Jun 28, 2010

WCF COMPLETE TUTORIAL

Getting Started

Welcome to the world of windows communication foundation. This section you will learn what is WCF and how it is differ from web service. Tools require setting up the environment for WCF development and great books on WCF also mention here.
  • Introduction to WCF
  • Development Tools
  • Difference between WCF and Web service

Introduction to WCF

Windows Communication Foundation (Code named Indigo) is a programming platform and runtime system for building, configuring and deploying network-distributed services. It is the latest service oriented technology; Interoperability is the fundamental characteristics of WCF. It is unified programming model provided in .Net Framework 3.0. WCF is a combined features of Web Service, Remoting, MSMQ and COM+. WCF provides a common platform for all .NET communication.
Below figures shows the different technology combined to form WCF.

Advantage

  1. WCF is interoperable with other services when compared to .Net Remoting,where the client and service have to be .Net.
  2. WCF services provide better reliability and security in compared to ASMX web services.
  3. In WCF, there is no need to make much change in code for implementing the security model and changing the binding. Small changes in the configuration will make your requirements.
  4. WCF has integrated logging mechanism, changing the configuration file settings will provide this functionality. In other technology developer has to write the code.

Disadvantage

Making right design for your requirement is little bit difficult. I will try to help you on solving these difficulties in the following article.

Development Tools

WCF application can be developed by the Microsoft Visual Studio. Visual studio is available at different edition. You can use Visual Studio 2008 Expression edition for the development.
Visual Studio 2008 SDK 1.1

Microsoft Visual Studio 2008

Microsoft Visual studio 2008 provides new features for WCF compared to Visual Studio 2005. These are the new features added to VS 2008.

  1. Multi-targeting

    You can create application in different framework like Framework 2.0, 3.0 and 3.5

  2. Default template is available for WCF


  3. WCF - Test Client tools for testing the WCF service.

    Microsoft provides inbuilt application to test the WCF application. This can be done by opening the Visual Studio command prompt and type the wcfClient Serviceurl shows below. This will help the developer to test the service before creating the client application.

  4. WCF services can be debugged now in Visual Studio 2008. Wcfsvchost.exe will do it for you because service will be self hosted when you start debugging.

    Difference between WCF and Web service

    Web service is a part of WCF. WCF offers much more flexibility and portability to develop a service when comparing to web service. Still we are having more advantages over Web service, following table provides detailed difference between them.
    Features Web Service WCF
    Hosting It can be hosted in IIS It can be hosted in IIS, windows activation service, Self-hosting, Windows service
    Programming [WebService] attribute has to be added to the class [ServiceContraact] attribute has to be added to the class
    Model [WebMethod] attribute represents the method exposed to client [OperationContract] attribute represents the method exposed to client
    Operation One-way, Request- Response are the different operations supported in web service One-Way, Request-Response, Duplex are different type of operations supported in WCF
    XML System.Xml.serialization name space is used for serialization System.Runtime.Serialization namespace is used for serialization
    Encoding XML 1.0, MTOM(Message Transmission Optimization Mechanism), DIME, Custom XML 1.0, MTOM, Binary, Custom
    Transports Can be accessed through HTTP, TCP, Custom Can be accessed through HTTP, TCP, Named pipes, MSMQ,P2P, Custom
    Protocols Security Security, Reliable messaging, Transactions

    WCF Fundamental

    In this part of tutorial you are going to learn about some fundamental concepts in WCF. These concepts and terms will be used throughout this tutorial.

    EndPoint

    WCF Service is a program that exposes a collection of Endpoints. Each Endpoint is a portal for communicating with the world.
    All the WCF communications are take place through end point. End point consists of three components.

    Address

    Basically URL, specifies where this WCF service is hosted .Client will use this url to connect to the service. e.g
    http://localhost:8090/MyService/SimpleCalculator.svc

    Binding

    Binding will describes how client will communicate with service. There are different protocols available for the WCF to communicate to the Client. You can mention the protocol type based on your requirements.
    A binding has several characteristics, including the following:
    • Transport -Defines the base protocol to be used like HTTP, Named Pipes, TCP, and MSMQ are some type of protocols.
    • Encoding (Optional) - Three types of encoding are available-Text, Binary, or Message Transmission Optimization Mechanism (MTOM). MTOM is an interoperable message format that allows the effective transmission of attachments or large messages (greater than 64K).
    • Protocol(Optional) - Defines information to be used in the binding such as Security, transaction or reliable messaging capability
    The following table gives some list of protocols supported by WCF binding.
    Binding Description
    BasicHttpBinding Basic Web service communication. No security by default
    WSHttpBinding Web services with WS-* support. Supports transactions
    WSDualHttpBinding Web services with duplex contract and transaction support
    WSFederationHttpBinding Web services with federated security. Supports transactions
    MsmqIntegrationBinding Communication directly with MSMQ applications. Supports transactions
    NetMsmqBinding Communication between WCF applications by using queuing. Supports transactions
    NetNamedPipeBinding Communication between WCF applications on same computer. Supports duplex contracts and transactions
    NetPeerTcpBinding Communication between computers across peer-to-peer services. Supports duplex contracts
    NetTcpBinding Communication between WCF applications across computers. Supports duplex contracts and transactions

    Contract

    Collection of operation that specifies what the endpoint will communicate with outside world. Usually name of the Interface will be mentioned in the Contract, so the client application will be aware of the operations which are exposed to the client. Each operation is a simple exchange pattern such as one-way, duplex and request/reply.
    Below figure illustrate the functions of Endpoint

    Example:

    Endpoints will be mentioned in the web.config file on the created service.
    <system.serviceModel>
<services>
      <service name="MathService"
        behaviorConfiguration="MathServiceBehavior">
       <endpoint
         address="http://localhost:8090/MyService/MathService.svc" contract="IMathService"
          binding="wsHttpBinding"/> 
    

          </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="MathServiceBehavior">
          <serviceMetadata httpGetEnabled="True"/>
          <serviceDebug includeExceptionDetailInFaults="true" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
    

     
    

    

    

Binding and Behavior
    

    

    

    

Binding
    

    
Simple definition for Binding describes how the client will 
communicate with service.  We can understand with an example.
    
Consider a scenario say, I am creating a service that has to be used 
by two type of client. One of the client will access SOAP using http and
 other client will access Binary using TCP. How it can be done?  With 
Web service it is very difficult to achieve, but in WCF its just we need
 to add extra endpoint in the configuration file.

    

    

    <system.serviceModel>
    <services>
      <service name="MathService"
        behaviorConfiguration="MathServiceBehavior">
      <endpoint address="http://localhost:8090/MyService/MathService.svc" 
        contract="IMathService"
          binding="wsHttpBinding"/>
<endpoint address="net.tcp://localhost:8080/MyService/MathService.svc" 
contract="IMathService"
          binding="netTcpBinding"/> 
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="MathServiceBehavior">
          <serviceMetadata httpGetEnabled="True"/>
          <serviceDebug includeExceptionDetailInFaults="true" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>

  
    

    
See how simple it is in WCF. Microsoft is making everything 
simple.cording to its scope: common behaviors affect all endpoints 
globally, service behaviors affect only service-related aspects, 
endpoint behaviors affect only endpoint-related properties, and 
operation-level behaviors affect particular operations.
    

    

    

Example:
    
In the below configuration information, I have 
mentioned the Behavior at Service level. In the service behavior I have 
mention the servieMetadata node with attribute httGetEnabled='true'. 
This attribute will specifies the publication of the service metadata. 
Similarly we can add more behavior to the service.
    

    

    <system.serviceModel>
    <services>
      <service name="MathService"
        behaviorConfiguration="MathServiceBehavior">
        <endpoint address="" contract="IMathService"
    

              binding="wsHttpBinding"/>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="MathServiceBehavior">
          <serviceMetadata httpGetEnabled="True"/>
          <serviceDebug includeExceptionDetailInFaults="true" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
    

    

    

Contracts and Service Host
    

    

    

    

Contracts
    

    
In WCF, all services are exposed as contracts. Contract is a 
platform-neutral and standard way of describing what the service does. 
Mainly there are four types of contracts available in WCF
    

    

    

Service Contract
    
Service contracts describe the 
operation that service can provide. For Eg, a Service provide to know 
the temperature of the city based on the zip code, this service is 
called as Service contract. It will be created using Service and 
Operational Contract attribute.
    

    
To know more on Service contract see Service contract tutorial.
    

    

    

Data Contract
    
Data contract describes the custom data 
type which is exposed to the client. This defines the data types, that 
are passed to and from service. Data types like int, string are 
identified by the client because it is already mention in XML schema 
definition language document, but custom created class or data types 
cannot be identified by the client e.g. Employee data type. By using 
DataContract we can make client to be aware of Employee data type that 
are returning or passing parameter to the method.
    

    
To know more on DataContract see DataContract
 tutorial.
    

    

    

Message Contract
    
Default SOAP message format is provided
 by the WCF runtime for communication between Client and service. If it 
is not meeting your requirements then we can create our own message 
format. This can be achieved by using Message Contract attribute.
    

    
To know more on Message Contract see Message contract tutorial.
    

    

    

Fault Contract
    
Suppose the service I consumed is not 
working in the client application. I want to know the real cause of the 
problem. How I can know the error? For this we are having Fault 
Contract. Fault Contract provides documented view for error occurred in 
the service to client. This helps us to easy identity, what error has 
occurred.
    

    
To know more on Fault Contract see Fault
 Contract tutorial.
    

    

    

Service Host
    

    

    
Service Host object is in the process of hosting the WCF service
 and registering endpoints. It loads the service configuration 
endpoints, apply the settings and start the listeners to handle the 
incoming request. System.ServiceModel.ServiceHost namespace hold 
this object. This object is created while self hosting the WCF service.
    
In the below example you can find that WCF service is self hosted 
using console application.
    

    

    //Creating uri for the hosting the service
Uri uri = new Uri("http://localhost/CategoryService");
//Creating the host object for MathService
  ServiceHost host = new ServiceHost(typeof(CategoryService), uri);
//Adding endpoint to the Host object
  host.AddServiceEndpoint(typeof(ICategoryService),new WSHttpBinding(), uri);
  host.Open(); //Hosting the Service
  Console.WriteLine("Waiting for client invocations");
  Console.ReadLine();
    

      host.Close();
    

    

      
    

    

    

    

Note: 
    

    
Application can be controlled either through coding, configuring or 
through combination of both. Specification mention in the configuration 
can also be overwritten in code.
    

    

    

    

    

Message and Channel
    

    

    

    

Message
    

    
WCF Message is the unit of data exchange between client and service. 
 It consists of several parts, including a body and headers.
    

    

    

WCF Runtime
    

    
WCF runtime is the set of object responsible for sending and 
receiving message. For example formatting the message, applying security
 and transmitting and receiving message using various protocol.
    

    

    

Channels:
    

    
Channels are the core abstraction for sending message to and 
receiving message from an Endpoint. Broadly we can categories channels 
as
    

    

Transport Channels - Handles sending and receiving message from 
network.  Protocols like HTTP, TCP name pipes and MSMQ.
    

    

Protocol Channels
    
- Implements SOAP based protocol by 
processing and possibly modifying message. e.g. WS-Security and 
WS-Reliability.
    

    

    

    

    

WCF Client and Metadata
    

    

    

    

WCF Client
    

    
WCF client is a client application creates to expose the service 
operations as method. Any application can host a WCF client, including 
an application that host a service. Therefore it is possible to create a
 service that includes WCF clients of other services.
    
A client application is a managed application that uses a WCF client 
to communicate with another application. To create a client application 
for a WCF service requires the following steps:
    

      

    1. Get the Proxy class and service end point information
      2. 

      

      
Using SvcUtil.exe we can create proxy class for the 
service and configuration information for endpoints. Example type the 
following sentence in the Visual studio command prompt, this will 
generate the class file and configuration file which contain information
 about the endpoints.
      
svcutil /language:vb /out:ClientCode.vb /config:app.config http://localhost:8090/MyService/SimpleCalculator.svc?wsdl
      

      

    2. Call operations.
      3. 
Add this class files in the client application. Then create the 
object for this class and invoke the service operation. Configuration 
information we got from the above step has to be added to the client 
application configuration file. When the client application calls the 
first operation, WCF automatically opens the underlying channel. This 
underlying channel is closed, when the object is recycled.
      

      

      

      //Creating the proxy on client side
MyCalculatorServiceProxy.MyServiceProxy proxy 
= new MyCalculatorServiceProxy.MyServiceProxy();
 Console.WriteLine("Counter: " + proxy.MyMethod());
      

      

      

    3. Close the WCF client object.
      4. 
After using the object created in the above steps, we have to dispose
 the object. Channel will be closed with the service, when the object is
 cleared.
    

    

    

Metadata
    

    
Characteristics of the service are described by the metadata. This 
metadata can be exposed to the client to understand the communication 
with service. Metadata can be set in the service by enabling the 
ServiceMetadata  node inside the servcieBehaviour node of the service 
configuration file.
    

    

    <system.serviceModel>
    <services>
      <service name="MathService"
        behaviorConfiguration="MathServiceBehavior">
        <endpoint address="" contract="IMathService"
          binding="wsHttpBinding"/>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="MathServiceBehavior">
    <serviceMetadata httpGetEnabled="True"/>
          <serviceDebug includeExceptionDetailInFaults="true" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
    

    
This metadata can be viewed while creating WCF client application 
using SvcUtil.exe
    

    

    

    

WCF Architecture
    

    

    
The following figure illustrates the major components of WCF.
    

    

    
Figure 1: WCF Architecture

    

    

    

Contracts
    

    
Contracts layer are next to that of 
Application layer. Developer will directly use this contract to develop 
the service. We are also going to do the same now. Let us see briefly 
what these contracts will do for us and we will also know that WCF is 
working on message system.
    

    

    

Service contracts 
    
- Describe about the operation that 
service can provide. Example, Service provided to know the temperature 
of the city based on the zip code, this service we call as Service 
contract. It will be created using Service and Operational Contract 
attribute.
    

    

    

Data contract
    
- It describes the custom data type which 
is exposed to the client. This defines the data types, are passed to and
 from service. Data types like int, string are identified by the client 
because it is already mention in XML schema definition language 
document, but custom created class or datatype cannot be identified by 
the client e.g. Employee data type. By using DataContract we can make 
client aware that we are using Employee data type for returning or 
passing parameter to the method.
    

    

    

Message Contract
    
- Default SOAP message format is 
provided by the WCF runtime for communication between Client and 
service. If it is not meeting your requirements then we can create our 
own message format. This can be achieved by using Message Contract 
attribute.
    

    

    

Policies and Binding
    
- Specify conditions required to 
communicate with a service e.g security requirement to communicate with 
service, protocol and encoding used for binding.
    

    

    

Service Runtime
    
- It contains the behaviors that occur 
during runtime of service.
    

      

    • Throttling Behavior- Controls how many messages are processed.
      • 

    • Error Behavior - Specifies what occurs, when internal error 
occurs on the service.
      • 

    • Metadata Behavior - Tells how and whether metadata is available 
to outside world.
      • 

    • Instance Behavior - Specifies how many instance of the service 
has to be created while running.
      • 

    • Transaction Behavior - Enables the rollback of transacted 
operations if a failure occurs.
      • 

    • Dispatch Behavior - Controls how a message is processed by the 
WCF Infrastructure.
      • 

    

    

    

    

Messaging
    
- Messaging layer is composed of channels. A 
channel is a component that processes a message in some way, for 
example, by authenticating a message. A set of channels is also known as
 a channel stack. Channels are the core abstraction for sending message 
to and receiving message from an Endpoint. Broadly we can categories 
channels as 
    

      

    • Transport Channels Handles sending and receiving message from
 network.  Protocols like HTTP, TCP, name pipes and MSMQ.
      • 

    • Protocol Channels Implements SOAP based protocol by 
processing and possibly modifying message. E.g. WS-Security and 
WS-Reliability.
      • 

    

    

    

    

Activation and Hosting
    
- Services can be hosted or 
executed, so that it will be available to everyone accessing from the 
client. WCF service can be hosted by following mechanism
    

      

    • IIS Internet information Service provides number of 
advantages if a Service uses Http as protocol. It does not require Host 
code to activate the service, it automatically activates service code.
      

 
      • 

    • Windows Activation Service (WAS) is the new process 
activation mechanism that ships with IIS 7.0. In addition to HTTP based 
communication, WCF can also use WAS to provide message-based activation 
over other protocols, such as TCP and named pipes.
      
 
      • 

    • Self-Hosting WCF service can be self hosted as console 
application, Win Forms or WPF application with graphical UI.
      
 
      • 

    • Windows Service WCF can also be hosted as a Windows Service, 
so that it is under control of the Service Control Manager (SCM).
      

      

      

      

      

WCF Hosting
      

      

      
In this part of the tutorial we are going to see the four 
different way of hosting the WCF service. WCF service cannot exist on 
its own; it has to be hosted in windows process called as host process. 
Single host process can host multiple servers and same service type can 
be hosted in multiple host process. As we discussed there are mainly 
four different way of hosting the WCF service.
      

Multiple hosting and protocols supported by WCF.Microsoft has 
introduced the WCF concept in order to make distributed application 
development and deployment simple.
      


      

      

      
  

      
     Hosting Environment
     Supported protocol
  
      

      
     Windows console and form application
     HTTP,net.tcp,net.pipe,net.msmq
  
      

      
     Windows service application (formerly known as NT services)
     HTTP,net.tcp,net.pipe,net.msmq
  
      

      
     Web server IIS6
     http, wshttp
  
      

      
     Web server IIS7 - Windows Process Activation Service (WAS)
     HTTP,net.tcp,net.pipe,net.msmq
  
      

      

      
A summary of hosting options and supported features. 
      


  
      

      

      
     Feature
     Self-Hosting
     IIS Hosting
     WAS Hosting
  
      

      
     Executable Process/ App Domain
     Yes
     Yes
     Yes
  
      

      
     Configuration
     App.config
     Web.config
     Web.config
  
      

      
     Activation
     Manual at startup
     Message-based
     Message-based
  
      

      
     Idle-Time Management
     No
     Yes
     Yes
  
      

      
     Health Monitoring
     No
     Yes
     Yes
  
      

      
     Process Recycling
     No
     Yes
     Yes
  
      

      
     Management Tools
     No
     Yes
     Yes
      

      

      

      

      

      

      

IIS 5/6 Hosting
      

      
The main advantage of hosting service in IIS is that, it will 
automatically launch the host process when it gets the first client 
request. It uses the features of IIS such as process recycling, idle 
shutdown, process health monitoring and message based activation. The 
main disadvantage of using IIS is that, it will support only HTTP 
protocol.
      
 
Let as do some hands on, to create service and host in IIS
      


      

      
Step 1:Start the Visual Studio 2008 and click 
File->New->Web Site. Select the 'WCF Service' and Location as 
http. This will directly host the service in IIS and click OK.
      


      

      
Step 2:
I have created sample HelloWorld service, which will accept name as 
input and return with 'Hello' and name. Interface and implementation of 
the Service is shown below. 
      
IMyService.cs

      

      

      [ServiceContract]
public interface IMyService
{
    [OperationContract]
    string HelloWorld(string name);    

}
      

      
MyService.cs

      

      public class MyService : IMyService
{

    #region IMyService Members

    public string HelloWorld(string name)
    {
        return "Hello " + name;
    }

    #endregion
}
      

      

      
Step 3:
Service file (.svc) contains name of the service and code behind file 
name. This file is used to know about the service.
      
MyService.svc

      

      

      <%@ ServiceHost Language="C#" Debug="true" 
Service="MyService" CodeBehind="~/App_Code/MyService.cs" %>
      

      

      

      
Step 4:
Server side configurations are mentioned in the config file. Here I have
 mention only one end point which is configured to 'wsHttpBinding', we 
can also have multiple end point with differnet binding. Since we are 
going to hosted in IIS. We have to use only http binding. We will come 
to know more on endpoints and its configuration in later tutorial.
Web.Config
      

      

      <system.serviceModel>
  <services>
   <service behaviorConfiguration="ServiceBehavior" name="MyService">
 <endpoint address="http://localhost/IISHostedService/MyService.svc" 
 binding="wsHttpBinding" contract="IMyService">
 <identity>
 <dns value="localhost"/>
 </identity>
 </endpoint>
 <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
   </service>
 </services>
 <behaviors>
  <serviceBehaviors>
    <behavior name="ServiceBehavior">
 <!-- To avoid disclosing metadata information, 
 set the value below to false and remove the 
 metadata endpoint above before deployment -->
      <serviceMetadata httpGetEnabled="true"/>
 <!-- To receive exception details in faults for 
 debugging purposes, set the value below to true.  
 Set to false before deployment to avoid disclosing exception information -->
 <serviceDebug includeExceptionDetailInFaults="false"/>
 </behavior>
   </serviceBehaviors>
  </behaviors>
</system.serviceModel>
      

      
Note:  
You need to mention the service file name, along with the Address 
mention in the config file.
IIS Screen shot
      


This screen will appear when we run the application.
      



      

      
Step 5:
Now we successfully hosted the service in IIS. Next we have to consume 
this service in client application. Before creating the client 
application, we need to create the proxy for the service. This proxy is 
used by the client application, to interact with service.
To create the proxy, run the Visual Studio 2008 command prompt. Using 
service utility we can create the proxy class and its configuration 
information.
      

      svcutil  http://localhost/IISHostedService/MyService.svc
      

      

After executing this command we will find two file generated in the 
default location.
      



      • 

    • MyService.cs - Proxy class for the WCF service
      • 

    • output.config - Configuration information about the service.
      • 

    

    
Step 6:
Now we will start creating the Console application using Visual Studio 
2008(Client application).
    


    

    
Step 7:
Add the reference 'System.ServiceModel'; this is the core dll for WCF.
    


    

    
Step 8:
Create the object for the proxy class and call the HelloWorld method. 
    

    

    static void Main(string[] args)
        {
            //Creating Proxy for the MyService 
             MyServiceClient client = new MyServiceClient();
             Console.WriteLine("Client calling the service...");
             Console.WriteLine(client.HelloWorld("Ram"));
             Console.Read();

        }
    

    

    

    
Step 9:
If we run the application we will find the output as shown below.
    

I hope you have enjoyed the Service hosted in IIS. Now let start the 
look on the self hosted service.
    

    

    

    

Self Hosting
    

    
In web service, we can host the service only in IIS, but WCF provides
 the user to host the service in any application (e.g. console 
application, Windows form etc.). Very interestingly developer is 
responsible for providing and managing the life cycle of the host 
process. Service can also be in-pro i.e. client and service in the same 
process. Now let's us create the WCF service which is hosted in Console 
application.  We will also look in to creating proxy using 'ClientBase'
 abstract class.
    
Note:  
Host process must be running before the client calls the service, which 
typically means you have to prelaunch it.
    

    
Step 1:
First let's start create the Service contract and it implementation. 
Create a console application and name it as MyCalculatorService. This is
 simple service which return addition of two numbers.
    


    

    
Step 2:
Add the System.ServiceModel reference to the project.
    


    

    
Step 3:
Create an ISimpleCalculator interface, Add ServiceContract and 
OperationContract attribute to the class and function as shown below. 
You will know more information about these contracts in later session. 
These contracts will expose method to outside world for using this 
service.
    
IMyCalculatorService.cs

    

    

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;

namespace MyCalculatorService
{
    [ServiceContract()]
    public interface ISimpleCalculator
    {
        [OperationContract()]
        int Add(int num1, int num2);
    }

}
    

    

    

    
Step 4:
MyCalculatorService is the implementation class for IMyCalculatorService
 interface as shown below.
    
MyCalculatorService.cs

    

    

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace MyCalculatorService
{
    class SimpleCalculator : ISimpleCalculator
    {
        public int Add(int num1, int num2)
        {
            return num1 + num2;
        }

    }
}
    

    

    

    
Step 5:
Now we are ready with service. Let's go for implementing the hosting 
process. Create a new console application and name it as 
'MyCalculatorServiceHost'
    


    

    
Step 6:
ServiceHost is the core class use to host the WCF service. It 
will accept implemented contract class and base address as contractor 
parameter. You can register multiple base addresses separated by commas,
 but address should not use same transport schema.
    

    

    Uri httpUrl 
= new Uri("http://localhost:8090/MyService/SimpleCalculator");

Uri tcpUrl 
= new Uri("net.tcp://localhost:8090/MyService/SimpleCalculator");

ServiceHost host 
= new ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl, tcpUrl);
    

    
Multiple end points can be added to the Service using AddServiceEndpoint()
 method. Host.Open() will run the service, so that it can be used
 by any client.
    
 

    

    
Step 7:
Below code show the implementation of the host process.
    

    

     
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
using System.ServiceModel.Description;

namespace MyCalculatorServiceHost
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a URI to serve as the base address
            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");
            //Create ServiceHost
            ServiceHost host 
            = new ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);
            //Add a service endpoint
            host.AddServiceEndpoint(typeof(MyCalculatorService.ISimpleCalculator)
            , new WSHttpBinding(), "");
            //Enable metadata exchange
            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            smb.HttpGetEnabled = true;
            host.Description.Behaviors.Add(smb);
            //Start the Service
            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());
            Console.WriteLine("Host is running... Press <Enter> key to stop");
            Console.ReadLine();

        }
    }
}
    

    

    

    
Step 8:
Service is hosted, now we need to implement the proxy class for the 
client. There are different ways of creating the proxy 
    

          

    • Using SvcUtil.exe, we can create the proxy class and 
configuration file with end points.
      • 
    

    • Adding Service reference to the client application.
      • 
    

    • Implementing ClientBase<T> class
      • 

    
 
Of these three methods, Implementing ClientBase<T> is 
the best practice. If you are using rest two method, we need to create 
proxy class every time when we make changes in Service implementation. 
But this is not the case for ClientBase<T>. It will create the 
proxy only at runtime and so it will take care of everything.
    
MyCalculatorServiceProxy.cs

    

    

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
using MyCalculatorService;
namespace MyCalculatorServiceProxy
{
    public class MyCalculatorServiceProxy : 
        //WCF create proxy for ISimpleCalculator using ClientBase
        ClientBase<ISimpleCalculator>,
        ISimpleCalculator
    {
        public int Add(int num1, int num2)
        {
            //Call base to do funtion
            return base.Channel.Add(num1, num2);
        }
    }
}
    

    

    

    
Step 9:
In the client side, we can create the instance for the proxy class and 
call the method as shown below.
Add proxy assembly as reference to the project.
    

    

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;

namespace MyCalculatorServiceClient
{
    class Program
    {
        static void Main(string[] args)
        {
            MyCalculatorServiceProxy.MyCalculatorServiceProxy proxy ;
            proxy= new MyCalculatorServiceProxy.MyCalculatorServiceProxy();
            Console.WriteLine("Client is running at " + DateTime.Now.ToString());
            Console.WriteLine("Sum of two numbers... 5+5 ="+proxy.Add(5,5));
            Console.ReadLine();
        }
    }
}
    

    

    

    
Step 10 :
End point (same as service) information should be added to the 
configuration file of the client application.
    

    

    <?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>
    <client>
      <endpoint address ="http://localhost:8090/MyService/SimpleCalculator" 
                binding ="wsHttpBinding"
                contract ="MyCalculatorService.ISimpleCalculator">
        
      </endpoint>
    </client>
  </system.serviceModel>
</configuration>
    

    

    
Step 11:
Before running the client application, you need to run the service. 
Output of the client application is shown below.
    

This self host shows advantage such as in-Pro hosting, 
programmatic access and it can be used when there need singleton 
service. I hope you have enjoyed the Self hosting session, now let go 
for hosting using Windows Activation service.
    

    

    

    

Windows Activation Service
    

    
Windows Activation service is a system service available with Windows
 vista and windows server 2008. It is available with IIS 7.0 and it is 
more powerful compared to IIS 6.0 because it supports Http, TCP and 
named pipes were IIS 6.0 supports only Http. It can be installed and 
configured separately.
    
Hosting WCF in Activation service takes many advantages such as 
process recycling, isolation, idle time management and common 
configuration system.  WAS hosted service can be created using following
 steps
    

      

    1. Enable WCF for non-http protocols
      2. 

    2. Create WAS hosted service
      3. 

    3. Enable different binding to the hosted service
      4. 

    

    

    

Enable WCF for non-http protocols
    
Before Start creating the service we need to configure the system to 
support WAS. Following are the step to configure WAS.
    

      

    1. Click Start -> Control Panel -> programs and Features and 
click 'Turn Windows Components On or Off' in left pane. 
      2. 

    2. Expand 'Microsoft .Net Framework 3.0' and enable "Windows 
Communication Foundation HTTP Activation" and "Windows Communication 
Foundation Non- HTTP Activation".
      3. 

    3. Next we need to add Binding to the Default Web site. As an 
example, we will bind the default web site to the TCP protocol. Go to 
the Start menu -> Programs ->Accessories. Right click on the 
"Command Prompt" item, and select "Run as administrator" from the 
context menu.
      4. 

    4. Execute the following command
      5. 


    5. 

      
C:\Windows\system32\inetsrv> 
appcmd.exe set site
    "Default Web Site" -+bindings.[protocol='net.tcp',
      
bindingInformation='808:*']
      6. 

    

    

    

    

    

    

    

    5. 

  5. That command adds the net.tcp site binding to the default web 
site by modifying the applicationHost.config file located in the "C:\Windows\system32\inetsrv\config"
 directory. Similarly we can add different protocols to the Default Web 
site.
    6. 







Create WAS hosted service

Step 1:
Next we are going to create the service, Open the Visual Studio 2008 and
 click New->WebSite and select WCF Service from the template and 
Location as HTTP as shown below.






Step 2:
Create the Contract by creating interface IMathService and add 
ServiceContract attribute to the interface and add OperationContract 
attribute to the method declaration.

IMathService.cs





using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

 [ServiceContract]
public interface IMathService
{

    [OperationContract]
    int Add(int num1, int num2);

    [OperationContract]
    int Subtract(int num1, int num2);

}







Step 3:
Implementation of the IMathService interface is shown below.

MathService.cs





using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

public class MathService : IMathService
{
    public int Add(int num1, int num2)
    {
        return num1 + num2;
    }

    public int Subtract(int num1, int num2)
    {
        return num1 - num2;
    }
}







Step 4:
Service file is shown below.

MathService.svc





<%@ ServiceHost Language="C#" Debug="true" Service="MathService" 
CodeBehind="~/App_Code/MathService.cs" %>







Step 5:
In web.Config file, create end point with 'netTcpBinding' binding and 
service metadata will be published using Metadata Exchange point. So 
create the Metada Exchange end point with address as 'mex' and binding 
as 'mexTcpBinding'. Without publishing the service Metadata we cannot 
create the proxy using net.tcp address (e.g svcutil.exe 
net.tcp://localhost/WASHostedService/MathService.svc
) 

Web.Config




<system.serviceModel>
<services>
 <service name="MathService" behaviorConfiguration="ServiceBehavior">
 <!-- Service Endpoints -->
 <endpoint binding="netTcpBinding" 
 contract="IMathService" >
 </endpoint>
  <endpoint address="mex" 
  binding="mexTcpBinding" contract="IMetadataExchange"/>
  </service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="ServiceBehavior">
<!-- To avoid disclosing metadata information, set the value below 
to false and remove the metadata endpoint above before deployment -->
 <serviceMetadata httpGetEnabled="true"/>
 <!-- To receive exception details in
  faults for debugging purposes, set the value below to true. 
   Set to false before deployment to avoid disclosing 
   exception information -->
 <serviceDebug includeExceptionDetailInFaults="false"/>
 </behavior>
</serviceBehaviors></behaviors>
</system.serviceModel>








Enable different binding to the hosted service


    

  1. Go to the Start menu -> Programs ->Accessories. Right 
click on the "Command Prompt" item, and select "Run as administrator" 
from the context menu.
    2. 

  2. Execute the following command
    C:\Windows\system32\inetsrv>appcmd set app "Default Web 
Site/WASHostedServcie" /enabledProtocols:http,net.tcp
    3. 


Output will be shown below.






Step 6:
Now the service is ready to use. Next we can create the proxy class 
using service uttility and add the proxy class to the client 
application. 
Creat the proxy class using Visual Studio Command prompt and execute the
 command

svcutil.exe net.tcp://localhost/WASHostedService/MathService.svc
Proxy and configuration file are generated in the corresponding 
location.






Step 6:
Create the client application as shown below and add the reference 'System.ServiceModel',
 this is the core dll for WCF.






Step 8: 
Add the proxy class and configuration file to the client application. 
Create the object for the MathServiceClient and call the method.

Program.cs
  




 class Program
    {
        static void Main(string[] args)
        {
            MathServiceClient client = new MathServiceClient();
            Console.WriteLine("Sum of two number 5,6");
            Console.WriteLine(client.Add(5,6));
            Console.ReadLine();

        }




    }



The output will be shown as below.


So this tutorial clearly explains about the hosting the WCF in 
Windows Activation Service. So next we can see how to host the service 
using Windows Service.








Windows Service Hosting





In this tutorial we are going to see the hosting WCF service in 
Windows service. We will use same set of code used for hosting the WCF 
service in Console application to this. This is same as hosting the 
service in IIS without message activated. There is some advantage of 
hosting service in Windows service.


    

  • The service will be hosted, when system starts
    • 

  • Process life time of the service can be controlled by Service 
Control Manager for windows service
    • 

  • All versions of Windows will support hosting WCF service.
    • 






Step 1:
Now let start create the WCF service, Open the Visual Studio 2008 and 
click New->Project and select Class Library from the template.






Step 2:
Add reference System.ServiceModel to the project. This is the 
core assembly used for creating the WCF service. 



Step 3:
Next we can create the ISimpleCalulator interface as shown below.
 Add the Service and Operation Contract attribute as shown below.

ISimpleCalculator.cs






using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;

namespace WindowsServiceHostedContract
{
    [ServiceContract]
    public interface ISimpleCalculator
    {
        [OperationContract]
        int Add(int num1, int num2);

        [OperationContract]
        int Subtract(int num1, int num2);

        [OperationContract]
        int Multiply(int num1,int num2);

        [OperationContract]
        double Divide(int num1, int num2);

    }
}







Step 4:
Implement the ISimpleCalculator interface as shown below.

SimpleCalulator.cs





using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace WindowsServiceHostedService
{
    class SimpleCalculator
        : ISimpleCalculator
    {
 
        public int Add(int num1, int num2)
        {
            return num1+num2;
        }

        public int Subtract(int num1, int num2)
        {
             return num1-num2;
        }

        public int Multiply(int num1, int num2)
        {
             return num1*num2;
        }

        public double Divide(int num1, int num2)
        {
            if (num2 != 0)
                return num1 / num2;
            else
                return 0;
        }


    }
}







Step 5:
Build the Project and get the dll. Now we are ready with WCF service, 
now we are going to see how to host the WCF Service in Windows service.
Note:
In this project, I have mention that we are creating both Contract and 
Service(implementation) are in same project. It is always good practice 
if you have both in different project.



Step 6:
Open Visual Studio 2008 and Click New->Project and select Windows 
Service.






Step 7:
Add the 'WindowsServiceHostedService.dll' as reference to the 
project. This assembly will going to act as service.






Step 8:
OnStart method of the service, we can write the hosting code for WCF. We
 have to make sure that we are using only one service host object. On 
stop method  you need to close the Service Host. Following code show how
 to host WCF service in Windows service.

WCFHostedWindowsService.cs





using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Linq;
using System.ServiceProcess;
using System.Text;
using System.ServiceModel;
using System.ServiceModel.Description;

namespace WCFHostedWindowsService
{
    partial class WCFHostedWindowsService : ServiceBase
    {
        ServiceHost m_Host;
        
        public WCFHostedWindowsService()
        {
            InitializeComponent();
        }

        protected override void OnStart(string[] args)
        {
            if (m_Host != null)
            {
                m_Host.Close();
            }
            //Create a URI to serve as the base address
            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");
            //Create ServiceHost
            m_Host = new ServiceHost
            (typeof(WindowsServiceHostedService.SimpleCalculator), httpUrl);
            //Add a service endpoint
            m_Host.AddServiceEndpoint
            (typeof(WindowsServiceHostedService.ISimpleCalculator), new WSHttpBinding(), "");
            //Enable metadata exchange
            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            smb.HttpGetEnabled = true;
            m_Host.Description.Behaviors.Add(smb);
            //Start the Service
            m_Host.Open();


        }

        protected override void OnStop()
        {
            if (m_Host != null)
            {
                m_Host.Close();
                m_Host = null;
            }
        }
        static void Main()
        {
            ServiceBase[] ServicesToRun;
            ServicesToRun = new ServiceBase[] 
   { 
    new WCFHostedWindowsService() 
   };
            ServiceBase.Run(ServicesToRun);

        }
    }
}







Step 9: 
In order to install the service we need to have the Installer class for 
the Windows service. So add new Installer class to the project, which is
 inherited from the Installer class. Please find the below code 
for mentioning the Service name, StartUp type etc of the service.

ServiceInstaller.cs






using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceProcess;
using System.Configuration.Install;
using System.ComponentModel;
using System.Configuration;


namespace WCFHostedWindowsService
{
    [RunInstaller(true)]
    public class WinServiceInstaller : Installer
    {
        private ServiceProcessInstaller process;
        private ServiceInstaller service;

        public WinServiceInstaller()
        {
            process = new ServiceProcessInstaller();
            process.Account = ServiceAccount.NetworkService;
            service = new ServiceInstaller();
            service.ServiceName = "WCFHostedWindowsService";
            service.DisplayName = "WCFHostedWindowsService";
            service.Description = "WCF Service Hosted";
            service.StartType = ServiceStartMode.Automatic;
            Installers.Add(process);
            Installers.Add(service);
        }
    }


}







Step 10:
Build the project, we will get the WCFHostedWindowsService.exe. 
Next we need to install the service using Visual Studio Command Prompt. 
So open the command prompt by clicking Start->All Programs-> 
Microsoft Visual Studio 2008-> Visual Studio Tools-> Visual Studio
 Command Prompt
Using installutil utility application, you can install the 
service as shown below.






Step 11:
Now service is Hosted sucessfully and we can create the proxy class for 
the service and start using in the client applcaiton.






Binding





Binding will describes how client will communicate with service.
 There are different protocols available for the WCF to communicate to 
the Client. You can mention the protocol type based on your 
requirements.

Binding has several characteristics, including the following:


    

  • TransportDefines the base protocol to be used like 
HTTP, Named Pipes, TCP, and MSMQ are some type of protocols.
    • 

  • Encoding (Optional)Three types of encoding are 
available-Text, Binary, or Message Transmission Optimization Mechanism 
(MTOM). MTOM is an interoperable message format that allows the 
effective transmission of attachments or large messages (greater than 
64K). 
    • 

  • Protocol(Optional)Defines information to be used in 
the binding such as Security, transaction or reliable messaging 
capability
    

    

    

    

    

Bindings and Channel Stacks
    

    

    
In WCF all the communication details are handled by channel, it 
is a stack of channel components that all messages pass through during 
runtime processing. The bottom-most component is the transport channel. 
This implements the given transport protocol and reads incoming messages
 off the wire. The transport channel uses a message encoder to read the 
incoming bytes into a logical Message object for further processing. 
    

    
Figure
 1: Bindings and Channel Stacks (draw new diagram)
    

    
After that, the message bubbles up through the rest of the 
channel stack, giving each protocol channel an opportunity to do its 
processing, until it eventually reaches the top and WCF dispatches the 
final message to your service implementation. Messages undergo 
significant transformation along the way.
    
It is very difficult for the developer to work directly with channel 
stack architecture. Because you have to be very careful while ordering 
the channel stack components, and whether or not they are compatible 
with one other.
    
So WCF provides easy way of achieving this using end point. In end 
point we will specify address, binding and contract. To know more about 
end point.  Windows Communication Foundation follows the instructions 
outlined by the binding description to create each channel stack. The 
binding binds your service implementation to the wire through the 
channel stack in the middle.
    

    

    

    
Types of Binding
    

    
Let us see more detailed on predefined binding
    



    

    
BasicHttpBinding
    

      

    • It is suitable for communicating with ASP.NET Web services 
(ASMX)-based services that comfort with WS-Basic Profile conformant Web 
services.
      • 

    • This binding uses HTTP as the transport and text/XML as the 
default message encoding.
      • 

    • Security is disabled by default
      • 

    • This binding does not support WS-* functionalities like WS- 
Addressing, WS-Security, WS-ReliableMessaging
      • 

    • It is fairly weak on interoperability.
      • 

    

    

    

    
WSHttpBinding
    

      

    • Defines a secure, reliable, interoperable binding suitable for 
non-duplex service contracts.
      • 

    • It offers lot more functionality in the area of 
interoperability. 
      • 

    • It supports WS-* functionality and distributed transactions with
 reliable and secure sessions using SOAP security.
      • 

    • It uses HTTP and HTTPS transport for communication.
      • 

    • Reliable sessions are disabled by default.
      • 

    

    

    

    
WSDualHttpBinding
    
This binding is same as that of WSHttpBinding, except it supports 
duplex service. Duplex service is a service which uses duplex message 
pattern, which allows service to communicate with client via callback.
    

In WSDualHttpBinding reliable sessions are enabled by default. It 
also supports communication via SOAP intermediaries.
    


    

    

    
WSFederationHttpBinding
    
This binding support federated security. It helps implementing 
federation which is the ability to flow and share identities across 
multiple enterprises or trust domains for authentication and 
authorization. It supports WS-Federation protocol.
    
 
    

    

    
NetTcpBinding
    
This binding provides secure and reliable binding environment for 
.Net to .Net cross machine communication. By default it creates 
communication stack using WS-ReliableMessaging protocol for reliability,
 TCP for message delivery and windows security for message and 
authentication at run time. It uses TCP protocol and provides support 
for security, transaction and reliability.
    

    

    
NetNamedPipeBinding
    
This binding provides secure and reliable binding environment for 
on-machine cross process communication. It uses NamedPipe protocol and 
provides full support for SOAP security, transaction and reliability. By
 default it creates communication stack with WS-ReliableMessaging for 
reliability, transport security for transfer security, named pipes for 
message delivery and binary encoding.
    

    


    
NetMsmqBinding
    

      

    • This binding provides secure and reliable queued communication 
for cross-machine environment. 
      • 

    • Queuing is provided by using MSMQ as transport.
      • 

    • It enables for disconnected operations, failure isolation and 
load leveling 
      • 

    

    

    

    
NetPeerTcpBinding
    

      

    • This binding provides secure binding for peer-to-peer 
environment and network applications. 
      • 

    • It uses TCP protocol for communication
      • 

    • It provides full support for SOAP security, transaction and 
reliability.
      • 

    

    

    

    
Binding configuration
    

    
Binding can be configured either through configuration file or 
Programming.  Let us see the binding representation in each method.
    


    
Administrative (Configuration file):
    
In the configuration file of the hosting application, you can add the
 <bindings> element inside the <system.serviceModel> element
 and add the properties to particular binding type. Properties 
corresponding to the particular binding type can be mentioned below. 
Name of the binding properties that you are going to use has to be 
mention in the end point.
    


    

    <system.serviceModel>
  <services>
   <service  name="MyService">
 <endpoint address="http://localhost/IISHostedService/MyService.svc" 
 binding="wsHttpBinding" bindingName="wshttpbind" contract="IMyService">
 <identity>
 <dns value="localhost"/>
 </identity>
 </endpoint>
 <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
    </service>
  </services>
  <bindings>
      <wsHttpBinding>
        <binding name="wshttpbind"  allowCookies="true" closeTimeout="00:01:00" 
        receiveTimeout="00:01:00" />
      </wsHttpBinding>
  </bindings>
</system.serviceModel>
    

    

    

    
Programming Model:
    
In the following code, I have created the WSHttpBinding object
 and assign the properties which to be configured. This binding object 
is added to the Service endpoint for client communication. Similarly you
 can also create any type of binding and add to endpoint.
    

    

    //Create a URI to serve as the base address
            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");
            //Create ServiceHost
            ServiceHost host =
             new ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);

            //Create Binding to add to end point
            WSHttpBinding wshttpbind = new WSHttpBinding();
            wshttpbind.AllowCookies = true;
            wshttpbind.CloseTimeout = new TimeSpan(0, 1, 0);
            wshttpbind.ReceiveTimeout  = new TimeSpan(0, 1, 0);

            //Add a service endpoint
            host.AddServiceEndpoint
            (typeof(MyCalculatorService.ISimpleCalculator), wshttpbind, "");
            //Enable metadata exchange
            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            smb.HttpGetEnabled = true;
            host.Description.Behaviors.Add(smb);
            //Start the Service
            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());
            Console.WriteLine("Host is running... Press  key to stop");
            Console.ReadLine();
    

    

    

    

    
Note:
It is always good if you configure the binding properties using 
configuration file, because while moving to the production you no need 
to change in the code and recompile it. It is always good practice to 
represent in the configuration file.
    

    

    

    
Metadata Exchange
    

    
WCF provides rich infrastructure for Exporting, Publishing, 
retrieving and Importing the metadata. WCF uses the Metadata to describe
 how to interact with the service endpoint. Using the metadata, client 
will create the proxy class for the service using SvcUtil.exe
    


    
Exporting Service Metadata
    
It is the process of describing 
the service endpoint so that client can understand how to use the 
service. 
    


    
Publishing Service Metadata
    
It is the process publishing 
metadata. It involves converting CLR type and binding information into 
WSDL or some other low level representation.
    


    
Retrieving Service Metadata
    
It is the process of retrieving 
the metadata. It uses WS-MetadataExcahge or HTTP protocol for retrieving
 the metadata.
Importing Service Metadata - It is the process of generating the 
abstract representation of the service using metadata.
    


    
Now we are going to focus mainly on publishing metadata. There 
are two way to publish metadata, either we can use HTTP-GET or through 
message exchange endpoint. By default service metadata is turn-off due 
to security reason. WCF metadata infrastructure resides in System.ServiceModel.Description
 namespace. Service metadata can be used for following purpose
    


      

    • Automatically generating the client for consuming service
      • 

    • Implementing the service description
      • 

    • Updating the binding for a client
      • 

    

    
Now let us understand the publishing the metadata using HTTP-GET
 method.
    

    

    

    

    
HTTP_GET Enabled Metadata
    

    
We will use ServiceBehaviour to publish the metadata using HTTP-GET. 
This can be configures either administratively or Programmatically. Http
 and Https can expose by appending "?wsdl" to the end of the service 
address. For example service address is http://localhost:9090/MyCalulatorService
 , HTTP-Get metadata address is given by http://localhost:9090/MyCalulatorService?wsdl.
    


    

    
Administrative (Configuration file):
    
In the below mention configuration information, you can find the 
behavior section in the ServiceBehavior. You can expose the metadata 
using ServiceMetadata node with httpGetEnable='True'.
    

    

    <system.serviceModel>
   <services>
 <service behaviorConfiguration="ServiceBehavior" name="MyService">
    <endpoint address="http://localhost/IISHostedService/MyService.svc"
     binding="wsHttpBinding" contract="IMyService">
  <identity>
  <dns value="localhost"/>
  </identity>
     </endpoint>
 </service>
  </services>
  <behaviors>
    <serviceBehaviors>
 <behavior name="ServiceBehavior">
   <!-Setting httpGetEnabled you can publish the metadata -->
  <serviceMetadata httpGetEnabled="true"/>
  </behavior>
     </serviceBehaviors>
   </behaviors>
</system.serviceModel>
    

    

    

    
Progarmming Model:
    
Using ServiceMetadataBehavior you can enable the metadata exchange. 
In the following code, I have created the ServiceMetadataBehavior object
 and assigned HttpGetEnabled property to true. Then you have to add the 
behavior to host description as shown. This set of code will publish the
 metadata using HTTP-GET.
    

           
    

     //Create a URI to serve as the base address
            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");
            //Create ServiceHost
            ServiceHost host = new 
            ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);
            //Add a service endpoint
            host.AddServiceEndpoint
            (typeof(MyCalculatorService.ISimpleCalculator), new WSHttpBinding(), "");
            //Enable metadata exchange
            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();

            //Enable metadata exchange using HTTP-GET
            smb.HttpGetEnabled = true;

            host.Description.Behaviors.Add(smb);
            //Start the Service
            host.Open();
            Console.WriteLine("Service is host at " + DateTime.Now.ToString());
            Console.WriteLine("Host is running... Press  key to stop");
            Console.ReadLine();
    

     
    

     
    

    

    
Metadata Exchange Endpoint
    

    
Exposing the metadata using HTTP-GET has a disadvantage, such that 
there is no guarantee that other platforms you interact will support it.
 There is other way of exposing the using special endpoint is called as 
Metadata Exchange Endpoint. You can have as many metadata exchange 
endpoints as you want.
    


    

    
Address
    
It is basically Uri to identify the metadata. 
You can specify as address in the endpoint but append with "mex" 
keyword. For example "http://localhost:9090/MyCalulatorService/mex"
    


    
Binding
    
There are four types of bindings supported for 
metadata exchange. They are mexHttpBinding, mexHttpsBinding, 
mexNamedPipesBinding, mexTcpBinding.
    


    
Contract
    
IMetadataExchange is the contract used for MEX 
endpoint. WCF service host automatically provides the implementation for
 this IMetadataExcahnge while hosting the service.
    
You can create the Metadata Exchange Endpoint either Administrative 
(configuration file) or programmatically.
    


    

    
Administrative (Configuration file):
    
In the configuration file of the hosting application, you can add 
metadata exchange endpoint as shown below.
    
 

    

    <system.serviceModel>
<services>
 <service name="MyService">
 <endpoint address="http://localhost/IISHostedService/MyService.svc"
 binding="wsHttpBinding" contract="IMyService">
 <identity>
 <dns value="localhost"/>
 </identity>
 </endpoint>
 <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
 </service>
</services>  
</system.serviceModel>
    

    

    

    

    
Programming Model:
    
In the following code I have mention about creating the Metadata 
Exchange Endpoint through coding. Steps to create the metadata endpoint 
are
    

    

      

    • Create the ServiceMetadataBehavior object and add to 
Service host description.
      • 

      

      ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            host.Description.Behaviors.Add(smb);
      

      

    • Create the metadata binding object using MetadataExchangeBinding
      • 

      

      Binding mexBinding = MetadataExchangeBindings.CreateMexHttpBinding ();
      

      

    • 3. Add the endpoint to the service host with address, binding and 
contract.
      • 

      

      host.AddServiceEndpoint(typeof(IMetadataExchange), mexBinding, "mex");
      

      

    

    
Complete code for hosting the service with metadata exchange endpoint
 is shown below.
    


    

    //Create a URI to serve as the base address
            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");
            //Create ServiceHost
            ServiceHost host = new 
            ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);
            //Add a service endpoint
            host.AddServiceEndpoint
            (typeof(MyCalculatorService.ISimpleCalculator), new WSHttpBinding(), "");
            //Enable metadata exchange
            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            host.Description.Behaviors.Add(smb);
            Binding mexBinding = MetadataExchangeBindings.CreateMexHttpBinding ();
            //Adding metadata exchange endpoint
            host.AddServiceEndpoint(typeof(IMetadataExchange), mexBinding, "mex");
            //Start the Service
            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());
            Console.WriteLine("Host is running... Press  key to stop");
            Console.ReadLine();
    

     
    

     
    

     
    

    

    
Contracts
    

    
Windows Communication Foundation (WCF, formerly known as Indigo) is 
built upon the foundation of web services messaging and related 
standards, while at the same time makes it possible to serialize 
messages in a more compact binary format, or in a more proprietary way. 
Still, the core message can always be represented in XML, therefore be 
considered compatible with any platform that understands XML, and agrees
 on the contract that defines said messaging between systems.
    

The contract is a platform-neutral and standard way of describing 
what the service does. WCF defines four types of contracts:
    



    

    

    
Service Contract
    

    

    
Service contract describes the operation that service provide. A
 Service can have more than one service contract but it should have at 
least one Service contract.
    
 
Service Contract can be define using [ServiceContract] and 
[OperationContract] attribute. [ServiceContract]  attribute is similar 
to the [WebServcie] attribute in the WebService and [OpeartionContract] 
is similar to the [WebMethod] in WebService.
    


      

    • It describes the client-callable operations (functions) exposed 
by the service 
      • 

    • It maps the interface and methods of your service to a 
platform-independent description 
      • 

    • It describes message exchange patterns that the service can have
 with another party. Some service operations might be one-way; others 
might require a request-reply pattern 
      • 

    • It is analogous to the  element in WSDL
      • 

    
To create a service contract you define an interface with related 
methods representative of a collection of service operations, and then 
decorate the interface with the ServiceContract Attribute to 
indicate it is a service contract. Methods in the interface that should 
be included in the service contract are decorated with the OperationContract
 Attribute.
    

    

    [ServiceContract()]
    public interface ISimpleCalculator
    {
        [OperationContract()]
        int Add(int num1, int num2);
    }
    

    
Once we define Service contract in the interface, we can create 
implement class for this interface.
    


    

    public  class SimpleCalculator : ISimpleCalculator
    {
    
        public int Add(int num1, int num2)
        {
            return num1 + num2;
        }

    }
    

    
With out creating the interface, we can also directly created the 
service by placing Contract in the implemented class. But it is not good
 practice of creating the service
    


    

    [ServiceContract()]
   public class SimpleCalculator 
   {
       [OperationContract()]
       public int Add(int num1, int num2)
       {
           return num1 + num2;
       }
    

    

    
   }
    

    
Now you have some fundamental idea on Service contract. Next we will 
look into Data Contract.
    

    

    

    
Data Contract
    

    

    
A data contract is a formal agreement between a service and a 
client that abstractly describes the data to be exchanged.
    

Data contract can be explicit or implicit. Simple type such as int, 
string etc has an implicit data contract. User defined object are 
explicit or Complex type, for which you have to define a Data contract 
using [DataContract]  and [DataMember] attribute.
    

A data contract can be defined as follows:
    
 
    

      

    • It describes the external format of data passed to and from 
service operations 
      • 

    • It defines the structure and types of data exchanged in service 
messages 
      • 

    • It maps a CLR type to an XML Schema 
      • 

    • t defines how data types are serialized and deserialized. 
Through serialization, you convert an object into a sequence of bytes 
that can be transmitted over a network. Through deserialization, you 
reassemble an object from a sequence of bytes that you receive from a 
calling application. 
      • 

    • It is a versioning system that allows you to manage changes to 
structured data
      • 

    
We need to include System.Runtime.Serialization reference to 
the project. This assembly holds the DataContract and DataMember
 attribute.
    

Create user defined data type called Employee. This data type should 
be identified for serialization and deserialization by mentioning with 
[DataContract] and [DataMember] attribute.
    


    

     [ServiceContract]
    public interface IEmployeeService
    {
        [OperationContract]
        Employee GetEmployeeDetails(int EmpId);
    }

    [DataContract]
    public class Employee
    {
        private string m_Name;
        private int m_Age;
        private int m_Salary;
        private string m_Designation;
        private string m_Manager;

        [DataMember]
        public string Name
        {
            get { return m_Name; }
            set { m_Name = value; }
        }

        [DataMember]
        public int Age
        {
            get { return m_Age; }
            set { m_Age = value; }
        }

        [DataMember]
        public int Salary
        {
            get { return m_Salary; }
            set { m_Salary = value; }
        }

        [DataMember]
        public string Designation
        {
            get { return m_Designation; }
            set { m_Designation = value; }
        }

        [DataMember]
        public string Manager
        {
            get { return m_Manager; }
            set { m_Manager = value; }
        }

    }
    

    
Implementation of the service class is shown below.  In GetEmployee 
method we have created the Employee instance and return to the client. 
Since we have created the data contract for the Employee class, client 
will aware of this instance whenever he creates proxy for the service.
    


    

    public class EmployeeService : IEmployeeService
    {
        public Employee GetEmployeeDetails(int empId)
        {
            
            Employee empDetail = new Employee();

            //Do something to get employee details and assign to 'empDetail' properties

            return empDetail;
        }
    }
    

    

    

    
Client side
    

    
On client side we can create the proxy for the service and make use 
of it. The client side code is shown below.
    


    protected void btnGetDetails_Click(object sender, EventArgs e)
        {
            EmployeeServiceClient objEmployeeClient = new EmployeeServiceClient();
            Employee empDetails;
            empDetails = objEmployeeClient.GetEmployeeDetails(empId);
//Do something on employee details
    

    

    

    
Message Contract
    

    

    
Message
    

    
Message is the packet of data which contains important 
information. WCF uses these messages to transfer information from Source
 to destination. 
    

WCF uses SOAP(Simple Object Access Protocol) Message format for 
communication. SOAP message contain Envelope, Header and Body.SOAP 
envelope contails name, namespace,header and body element. SOAP Hear 
contain important information which are not directly related to message.
 SOAP body contains information which is used by the target.
    
Diagram Soap envelope

    

    
Message Pattern
    
It describes how the programs will exchange message each other. There
 are three way of communication between source and destination
    


      

    1. Simplex - It is one way communication. Source will send 
message to target, but target will not respond to the message.
      2. 

    2. Request/Replay - It is two way communications, when 
source send message to the target, it will resend response message to 
the source. But at a time only one can send a message
      3. 

    3. Duplex - It is two way communication, both source and 
target can send and receive message simultaniouly.
      4. 

    

    
What is Message contract?
    
As I said earlier, WCF uses SOAP message for communication. Most of 
the time developer will concentrate more on developing the DataContract,
 Serializing the data, etc. WCF will automatically take care of message.
 On Some critical issue, developer will also require control over the 
SOAP message format. In that case WCF provides Message Contract to 
customize the message as per requirement.
    

WCF supports either RPC(Remote Procedure Call) or Message style 
operation model. In the RPC model, you can develop operation with Ref 
and out parameter. WCF will automatically create the message for 
operation at run time. In Message style operation WCF allows to 
customize the message header and define the security for header and body
 of the message.
    


    

    

    
Defining Message Contract
    
Message contract can be applied to type using MessageContract 
attribute. Custom Header and Body can be included to message using 
'MessageHeader' and 'MessageBodyMember'atttribute. Let us see the
 sample message contract definition.
    


    

    [MessageContract]
public class EmployeeDetails
{
    [MessageHeader]
    public string EmpID;
    [MessageBodyMember]
    public string Name;
    [MessageBodyMember]
    public string Designation;
    [MessageBodyMember]
    public int Salary;
    [MessageBodyMember]
    public string Location;
}
    

    
When I use this EmployeeDeatils type in the service operation as 
parameter. WCF will add extra header call 'EmpID' to the SOAP envelope. 
It also add Name, Designation, Salary, Location as extra member to the 
SOAP Body.
    
 

    

    

    
Rules :
    
You have to follow certain rules while working with Message contract
    

    

      

    1. When using Message contract type as parameter, Only one 
parameter can be used in servicie Operation

      

      [OperationContract]
void SaveEmployeeDetails(EmployeeDetails emp);
      

      

      2. 

    2. Service operation either should return Messagecontract type or it 
should not return any value

      

      [OperationContract]
EmployeeDetails GetEmployeeDetails();
      

      

      3. 

    3. Service operation will accept and return only message contract type.
 Other data types are not allowed.

      

      [OperationContract]
EmployeeDetails ModifyEmployeeDetails(EmployeeDetails emp);
 
      

      

      4. 

    

    

    
Note:
If a type has both Message and Data contract, service operation will 
accept only message contract.
    

    

    

    
Fault Contract
    

    

    
Service that we develop might get error in come case. This error
 should be reported to the client in proper manner. Basically when we 
develop managed application or service, we will handle the exception 
using try- catch block. But these exceptions handlings are technology 
specific.
    
    
In order to support interoperability and client will also be 
interested only, what wents wrong? not on how and where cause the error.
    

 
By default when we throw any exception from service, it will not 
reach the client side. WCF provides the option to handle and convey the 
error message to client from service using SOAP Fault contract.
    

Suppose the service I consumed is not working in the client 
application. I want to know the real cause of the problem. How I can 
know the error? For this we are having Fault Contract. Fault Contract 
provides documented view for error accorded in the service to client. 
This help as to easy identity the what error has accord. Let us try to 
understand the concept using sample example. 
    

Step 1: I have created simple calculator service with Add 
operation which will throw general exception as shown below
    

    

    //Service interface
[ServiceContract()]
    public interface ISimpleCalculator
    {
        [OperationContract()]
        int Add(int num1, int num2);
    }
//Service implementation
public  class SimpleCalculator : ISimpleCalculator
    {
    
        public int Add(int num1, int num2)
        {
            //Do something
            throw new Exception("Error while adding number");
            
        }

    }

    

    
Step 2: On client side code. Exceptions are handled using 
try-Catch block. Even though I have capture the exception when I run the
 application. I got the message that exceptions are not handled 
properly.
    


    

    try
   {
      MyCalculatorServiceProxy.MyCalculatorServiceProxy proxy
       = new MyCalculatorServiceProxy.MyCalculatorServiceProxy();
      Console.WriteLine("Client is running at " + DateTime.Now.ToString());
      Console.WriteLine("Sum of two numbers... 5+5 =" + proxy.Add(5, 5));
      Console.ReadLine();
   }
   catch (Exception ex) 
   {
      Console.WriteLine(ex.Message);
      Console.ReadLine();
   }
    

    

    

    
Step 3: Now if you want to send exception information form 
service to client, you have to use FaultException as shown below.
    


    

            public int Add(int num1, int num2)
        {
            //Do something
            throw new FaultException("Error while adding number");
            
        }
    

    
Step 4: Output window on the client side is show below.
    


    

    
Step 5: You can also create your own Custom type and send the 
error information to the client using FaultContract.
These are the steps to be followed to create the fault contract.
    


      

    • Define a type using the data contract and specify the fields you
 want to return. 
      • 

    • Decorate the service operation with the FaultContract attribute 
and specify the type name.
      • 

    • Raise the exception from the service by creating an instance and
 assigning properties of the custom exception.
      • 

    
Step 6: Defining the type using Data Contract
    


    

        [DataContract()]
    public class CustomException
    {
        [DataMember()]
        public string Title;
        [DataMember()]
        public string ExceptionMessage;
        [DataMember()]
        public string InnerException;
        [DataMember()]
        public string StackTrace;        
    }
    

    
Step 7: Decorate the service operation with the FaultContract
    


    

        [ServiceContract()]
    public interface ISimpleCalculator
    {
        [OperationContract()]
        [FaultContract(typeof(CustomException))]
        int Add(int num1, int num2);
    }
    

    
Step 8: Raise the exception from the service
    


    

            public int Add(int num1, int num2)
        {
            //Do something
            CustomException ex = new CustomException();
            ex.Title = "Error Funtion:Add()";
            ex.ExceptionMessage = "Error occur while doing add function.";
            ex.InnerException = "Inner exception message from serice";
            ex.StackTrace = "Stack Trace message from service.";
            throw new FaultException(ex,"Reason: Testing the Fault contract") ;
            
        }
    

    
Step 9: On client side, you can capture the service exception 
and process the information, as shown below.
    


    

       try
   {
      MyCalculatorServiceProxy.MyCalculatorServiceProxy proxy 
      = new MyCalculatorServiceProxy.MyCalculatorServiceProxy();
       Console.WriteLine("Client is running at " + DateTime.Now.ToString());
       Console.WriteLine("Sum of two numbers... 5+5 =" + proxy.Add(5, 5));
       Console.ReadLine();
    }
    catch (FaultException<MyCalculatorService.CustomException> ex)
     {
        //Process the Exception
     }
    

    

    

    

    

    
Instance Management
    

    
Instance management refers to the way a service handles a request 
from a client. Instance management is set of techniques WCF uses to bind
 client request to service instance, governing which service instance 
handles which client request. It is necessary because application will 
differ in their need for scalability, performance, durability, 
transaction and queued calls.
    

Basically there are three instance modes in WCF:
    




    
Configuration:
    
Instance mode can be configured using ServiceBehavior 
attribute. This can be specified at implementing the service contract as
 shown below.
    


    

     [ServiceContract()]
    public interface IMyService
    {
        [OperationContract]
        int MyMethod();
    }

   
    [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]
    public class MyService:IMyService
    {

        public int MyMethod()
        {
            //Do something
        }       
    }
    

    

    

    

    

    

    
Per-Call Service
    

    

    
When WCF service is configured for Per-Call instance mode, 
Service instance will be created for each client request.  This Service 
instance will be disposed after response is sent back to client.
    


Following diagram represent the process of handling the request from 
client using Per-Call instance mode.
    


    
Let as understand the per-call instance mode using example.
    


    
Step 1:
Create the service contract called IMyService and implement the 
interface.  Add service behavior attribute to the service class and set 
the InstanceContextMode property to PerCall as show below.
    

 

    

        [ServiceContract()]
    public interface IMyService
    {
        [OperationContract]
        int MyMethod();
    }
    

    

    

    
Step 2:
In this implementation of MyMethod operation, increment the static 
variable(m_Counter). Each time while making call to the service, 
m_Counter variable is incremented and return the value to the client.
    


    

        [ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall)]
    public class MyService:IMyService
    {
        static int m_Counter = 0;

        public int MyMethod()
        {
            m_Counter++;
            return m_Counter;
        }       
    }
 
    

    

    

    
Step 3:
Client side, create the proxy for the service and call "myMethod" 
operation multiple time.
    
 

    

            static void Main(string[] args)
        {
            Console.WriteLine("Service Instance mode: Per-Call");
            Console.WriteLine("Client  making call to service...");
            //Creating the proxy on client side
            MyCalculatorServiceProxy.MyServiceProxy proxy =
             new MyCalculatorServiceProxy.MyServiceProxy();
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.ReadLine();
}
    

    
Surprisingly, all requests to service return '1', because we 
configured the Instance mode to Per-Call. Service instance will created 
for each request and value of static variable will be set to one. While 
return back, service instance will be disposed. Output is shown below.
    


    
Fig: PercallOutput.
    

    

    

    
Per-Session Service
    

    

    
When WCF service is configured for Per-Session instance mode, 
logical session between client and service will be maintained. When the 
client creates new proxy to particular service instance, a dedicated 
service instance will be provided to the client. It is independent of 
all other instance. 
    

Following diagram represent the process of handling the request from 
client using Per-Session instance mode.
    


Let as understand the Per-Session instance mode using example.
    

    
Step 1:
Create the service contract called IMyService and implement the 
interface.  Add service behavior attribute to the service class and set 
the InstanceContextMode property to PerSession as show 
below. 
    


    

        [ServiceContract()]
    public interface IMyService
    {
        [OperationContract]
        int MyMethod();
    }
    

    

    

    
Step 2:
   In this implementation of MyMethod operation, increment the static 
variable (m_Counter). Each time while making call to the service, 
m_Counter variable will be incremented and return the value to the 
client. 
    


    

        [ServiceBehavior(InstanceContextMode=InstanceContextMode.PerSession)]
    public class MyService:IMyService
    {
        static int m_Counter = 0;

        public int MyMethod()
        {
            m_Counter++;
            return m_Counter;
        }       
    }
    

    

    

    
Step 3:
Client side, create the proxy for the service and call "myMethod" 
operation multiple time.
    
 

    

            static void Main(string[] args)
        {
            Console.WriteLine("Service Instance mode: Per-Session");
            Console.WriteLine("Client  making call to service...");
            //Creating the proxy on client side
            MyCalculatorServiceProxy.MyServiceProxy proxy = 
            new MyCalculatorServiceProxy.MyServiceProxy();
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.ReadLine();
        }
    

    
All request to service return incremented value (1, 2, 3, 4), because
 we configured the instance mode to Per-Session. Service instance will 
be created once the proxy is created at client side. So each time 
request is made to the service, static variable is incremented. So each 
call to MyMethod return incremented value. Output is shown below.
    


    
Fig: PersessionOutput.
    

    

    

    
Singleton Service
    

    

    
When WCF service is configured for Singleton instance mode, all 
clients are independently connected to the same single instance. This 
singleton instance will be created when service is hosted and, it is 
disposed when host shuts down.
    

Following diagram represent the process of handling the request from 
client using Singleton instance mode.
    


Let as understand the Singleton Instance mode using example.
    

    
Step 1:
Create the service contract called IMyService and implement the 
interface.  Add service behavior attribute to the service class and set 
the InstanceContextMode property to Single as show below. 
    


    

        [ServiceContract()]
    public interface IMyService
    {
        [OperationContract]
        int MyMethod();
    }
    

    

    

    
Step 2:
      In this implementation of MyMethod operation, increment the static
 variable(m_Counter). Each time while making call to the service, 
m_Counter variable is incremented and return the value to the client
    

   
    

        [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]
    public class MyService:IMyService
    {
        static int m_Counter = 0;

        public int MyMethod()
        {
            m_Counter++;
            return m_Counter;
        }       
    }
    

    

    

    

Step 3:
Client side, create the two proxies for the service and made a multiple 
call to MyMethod.
    
  
  
    

    static void Main(string[] args)
        {
Console.WriteLine("Service Instance mode: Singleton");
            Console.WriteLine("Client 1 making call to service...");
            //Creating the proxy on client side
            MyCalculatorServiceProxy.MyServiceProxy proxy = 
            new MyCalculatorServiceProxy.MyServiceProxy();
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.WriteLine("Counter: " + proxy.MyMethod());
            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Client 2 making call to service...");
            //Creating new proxy to act as new client
            MyCalculatorServiceProxy.MyServiceProxy proxy2 =
             new MyCalculatorServiceProxy.MyServiceProxy();
            Console.WriteLine("Counter: " + proxy2.MyMethod());
            Console.WriteLine("Counter: " + proxy2.MyMethod());
            Console.ReadLine();
  }
  
    

    
When two proxy class made a request to service, single instance at 
service will handle it and it return incremented value (1, 2, 3, 4), 
because instance mode is configured to 'Single'. Service instance is 
created when it is hosted. So this instance will remain till host is 
shutdown. Output is shown below.
    
 

    
Fig: SingletonOutput.
    

    

    

    
Instance Deactivation
    

    

    
In Instance Management System tutorial, you learn how to create 
sessionful  service instance. Basically service instance is hosted in a 
context. Session actually correlated the client message not to the 
instance, but to the context that host it. When session starts, context 
is created and when it closes, context is terminated. WCF provides the 
option of separating the two lifetimes and deactivating the instance 
separately  from its context.
    
 
ReleaseInstanceMode property of the OberationalBehavior
 attribute used to control the instance in relation to the method call.
    

 
Followings are the list Release mode available in the ReleaseInstanceMode
    


      

    1. RealeaseInstanceMode.None
      2. 

    2. RealeaseInstanceMode.BeforeCall
      3. 

    3. RealeaseInstanceMode.AfterCall
      4. 

    4. RealeaseInstanceMode.BeforeAndAfterCall
      5. 

    

    

    
Below code show, how to add the 'ReleaseInstanceMode' property 
to the operational behavior.
    


    

        [ServiceContract()]
    public interface ISimpleCalculator
    {
        [OperationContract()]
        int Add(int num1, int num2);
    }
   [OperationBehavior(ReleaseInstanceMode=ReleaseInstanceMode.BeforeCall]
    public int Add(int num1, int num2)
    {
        return num1 + num2;            
    }
    

    

    

    


    
ReleaseInstanceMode.None
    
This property means that it will not affect the instance lifetime. By
 default ReleaseInstanceMode property is set to 'None'.
    
 

    

    


    
ReleaseInstanceMode.BeforeCall
    
This property means that it will create new instance before a call is
 made to the operation.
    

If the instance is already exist,WCF deactivates the instance and calls 
Dispose() before the call is done. This is designed to optimize a method
 such as Create()

    
 

    

    


    
ReleaseInstanceMode.AfterCall
    
This property means that it will deactivate the instance after call 
is made to the method.
    

This is designed to optimize a method such a Cleanup()
    
 

    

    


    
ReleaseInstanceMode.BeforeAndAfterCall
    
This is means that it will create new instance of object before a 
call and deactivates the instance after call. This has combined effect 
of using ReleaseInstanceMode.BeforeCall and ReleaseInstanceMode.AfterCall
    

 

    

    

    
Explicit Deactivate
    
You can also explicitly deactivate instance using InstanceContext
 object as shown below.
    


    

       [ServiceContract()]
    public interface IMyService
    {
        [OperationContract]
        void MyMethod();
    }

   
    [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]
    public class MyService:IMyService
    {

        public void MyMethod()
        {
           //Do something
           OperationContext.Current.InstanceContext.ReleaseServiceInstance();
            
        }       
    }
    

     
    

    

    
Durable Service
    

    

    
Durable services are WCF services that persist service state 
information even after service host is restarted or Client.  It means 
that durable services have the capability to restore their own state 
when they are recycled. It can use data store like SQL database for 
maintain instance state. It is new feature in .Net 3.5
    

You might think that we can also maintain session using WCF sessions,
 but content in the session environment is not persisted by default. If 
the service is shut down or client closes the proxy, data will be lost. 
But in case of Durable service it is still maintained.
    

    

    
Working:
    
When Durable service is created with database as data store, it will 
maintain all its state information in the table.
    

When a client make a request to the service, instance of the service 
is serialized, a new GUID is generated. This serialized instance xml and
 key will be saved in the database. We will call this GUID as 
instanceID. Service will send the instanceID to the client, so later it 
can use this id to get the instance state back. Even when client is shut
 down, instanceId will be saved at the client side. So when ever client 
opening the proxy, it can get back the previous state.
    

    

    
Defining the Durable Service
    
Durable service can be implemented using [DurableService()] 
attribute. It takes 'CanCreateInstance' and 'CompletesInstance' property
 to mention on which operation instance state has to be saved and 
destroyed.
    


      

    • CanCreateInstance = true: Calling this operation results 
in creating the serialization and inserting it into the datastore.
      • 

    • CompletesInstance = true: Calling this operation results 
in deleting the persisted instance from the datastore.
      • 

    

    

    

        [Serializable]
    [DurableService()]
    public class MyService :IMyservice
    {
        [DurableOperation(CanCreateInstance = true)]
        public int StartPersistance()
        {
            //Do Something
        }

     [DurableOperation(CompletesInstance = true)]
        public void EndPersistence()
        {
            //Do Something
        }
    }
    

     
    

    

    
How to Create Durable Service
    

    
Let us understand more about the durable service by creating Simple 
Calculator service which persist the instance state in SQL server 
database.
    
 

    
Step 1:
Start the Visual Studio 2008 and click File->New->Web Site. Select
 the 'WCF Service' as shown below.
    



    

    
Step 2:
Create interface and decorate with Service and Operation contract.
    


    

        [ServiceContract()]
    public interface ISimpleCalculator
    {
        [OperationContract]
        int Add(int num);

        [OperationContract]
        int Subtract(int num);

        [OperationContract]
        int Multiply(int num);

        [OperationContract]
        void EndPersistence();
    }
 
    

    

    

    
Step 3:
You need to add [Serializable] And [DurableService()] attribute to the 
service implementation. Set CanCreateInstance = true property to the 
operation in which instance state has to be persisted and set 
CompletesInstance = true when state has to be destroyed. In this 
implementation, we are going to persist the 'currentValue' variable 
value to the database.
    


    

    using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;
using System.ServiceModel.Description;
    [Serializable]
    [DurableService()]
    public class SimpleCalculator :ISimpleCalculator 
    {
        int currentValue = default(int);
        [DurableOperation(CanCreateInstance = true)]
        public int Add(int num)
        {
            return (currentValue += num);
        }
        [DurableOperation()]
        public int Subtract(int num)
        {
            return (currentValue -= num);
        }
        [DurableOperation()]
        public int Multiply(int num)
        {
            return (currentValue *= num);
        }
        [DurableOperation(CompletesInstance = true)]
        public void EndPersistence()
        {
        }
    

    

    

    
Step 4:
Before configuring the database information in the durable service, you 
need to set up DataStore environment. Microsoft provides inbuilt 
sqlPersistance provider. To set up the database environment, run the 
these sql query  located at following location 
'C:\Windows\Microsoft.NET\Framework\v3.5\SQL\EN'
    


      

    • SqlPersistenceProviderSchema.sql
      • 

    • SqlPersistenceProviderLogic.sql
      • 

    

    

    
Step 5:
In order to support durable service, you need to use Context binding 
type. <persistenceProvider> tag is 
used to configure the persistence provider.
    


    

    <system.serviceModel>
 <services>
  <service name="SimpleCalculator" behaviorConfiguration="ServiceBehavior">
  <!-- Service Endpoints -->
  <endpoint address="" binding="wsHttpContextBinding" 
  bindingConfiguration="browConfig" contract="ISimpleCalculator">
  <identity>
  <dns value="localhost"/>
  </identity>
  </endpoint>
  <endpoint address="mex" binding="mexHttpBinding" 
  contract="IMetadataExchange"/>
  </service>
 </services>
 <behaviors>
  <serviceBehaviors>
  <behavior name="ServiceBehavior">
  <serviceMetadata httpGetEnabled="true"/>
 <serviceDebug includeExceptionDetailInFaults="true"/>
    <persistenceProvider  
     type="System.ServiceModel.Persistence.SqlPersistenceProviderFactory,
        System.WorkflowServices, Version=3.5.0.0, Culture=neutral,
         PublicKeyToken=31bf3856ad364e35" connectionStringName="DurableServiceStore" 
                               persistenceOperationTimeout="00:00:10"
                               lockTimeout="00:01:00"
                               serializeAsText="true"/>
   </behavior>
   </serviceBehaviors>
  </behaviors>
    <bindings>
      <wsHttpContextBinding >
        <binding name="browConfig" >
          <security mode="None"></security>
        </binding>
      </wsHttpContextBinding>
    </bindings>
</system.serviceModel>
<connectionStrings>
<add name="DurableServiceStore" 
connectionString="Data Source=saravanakumar;Initial Catalog
    

    =DurableServiceStore;Integrated Security=True"/>
</connectionStrings>
    

    

    
Step 6:
Create the console client application and name it as 
DurableServiceClient
    

    

    

    
Throttling
    

    
WCF throttling provides some properties that you can use to limit how
 many instances or sessions are created at the application level.  
Performance of the WCF service can be improved by creating proper 
instance.
    


    
  

    
     Attribute
     Description 
  
    

    
     maxConcurrentCalls
     Limits the total number of calls that can currently be in 
progress across all service instances. The default is 16.
  
    

    
     maxConcurrentInstances
     The number of InstanceContext objects that execute at one time 
across a ServiceHost. The default is Int32.MaxValue.
  
    

    
     maxConcurrentSessions
     A positive integer that limits the number of sessions a 
ServiceHost object can accept. 
The default is 10.

  
    

    
Service Throttling can be configured either Adminstractive or 
Programatically
    


    
Administrative(configuration file)
    

    
Using <serviceThrottling> 
tag of the Service Behavior, you can configure the maxConcurrentCalls, maxConcurrentInstances
 , maxConcurrentSessions property as shown below.
    


    

    <system.serviceModel>
    <services >
      <service behaviorConfiguration="ServiceBehavior"  name="MyService">
        <endpoint address="" binding="wsHttpBinding" contract="IMyService">
          <identity>
            <dns value="localhost"/>
          </identity>
        </endpoint>
        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="ServiceBehavior">
          <serviceMetadata httpGetEnabled="true"/>
          <serviceDebug includeExceptionDetailInFaults="true "/>
          <serviceThrottling maxConcurrentCalls="500"
 maxConcurrentInstances ="100" 
maxConcurrentSessions ="200"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
    

    

    

    

    
Programming Model
    
Use ServiceThrottlingBehavior object to set concurrent calls, session
 and instance property.
    


    

               ServiceHost host = new ServiceHost(typeof(MyService));
           ServiceThrottlingBehavior throttle
 = host.Description.Behaviors.Find();
            if (throttle == null)
            {
                throttle = new ServiceThrottlingBehavior();
                throttle.MaxConcurrentCalls = 500;
                throttle.MaxConcurrentSessions = 200;
                throttle.MaxConcurrentInstances = 100;
                host.Description.Behaviors.Add(throttle);
            }

            host.Open();
    

    
   
    

    

    
Operations
    

    

    
In classic object or component- oriented programming model 
offered only single way for client to call a method. Client will issue a
 call, block while the call was in progress, and continue executing once
 the method returned.
    

WCF will support classical Request-Replay model, along with that it 
also supports One-Way call(call and forget operation) and 
callback(service to call back the client)
    

Three modes of communication between client and service are
    


      

    1. Request- Replay
      2. 

    2. One-Way
      3. 

    3. Callback
      4. 

    

    

    

    

    

    

    
   
    

    

    

    

     
    

    

     
    

    

    
Request-Reply
    

    

    
By default all WCF will operated in the Request-Replay mode. It 
means that, when client make a request to the WCF service and client 
will wait to get response from service (till receiveTimeout). 
After getting the response it will start executing the rest of the 
statement.  If service doesn't respond to the service within 
receiveTimeout, client will receive TimeOutException.
    

Apart from NetPeerTcpBinding and the NetMsmqBinding all
 other bindings will support request-reply operations.
    


    

    

    

    

    

    

    

    

    

    

    

    
One-Way
    

    

    
In One-Way operation mode, client will send a request to the 
server and does not care whether it is success or failure of service 
execution. There is no return from the server side, it is one-way 
communication.
    
 
Client will be blocked only for a moment till it dispatches its call 
to service. If any exception thrown by service will not reach the 
server.
    
 
Client can continue to execute its statement, after making one-way 
call to server. There is no need to wait, till server execute. Sometime 
when one-way calls reach the service, they may not be dispatched all at 
once but may instead be queued up on the service side to be dispatched 
one at a time, according to the service's configured concurrency mode 
behavior. If the number of queued messages has exceeded the queue's 
capacity, the client will be blocked even if it's issued a one-way call.
 However, once the call is queued, the client will be unblocked and can 
continue executing, while the service processes the operation in the 
background.
    
 

    

    

    
Definition :
    
One-way operation can be enabled by setting IsOneWay property to true
 in Operation contract attribute.
    


    

    [ServiceContract]
public interface IMyService
{
    [OperationContract(IsOneWay=true)]
    void MyMethod(EmployeeDetails emp);
}
    

    

    

    


    
One-Way Operations and Sessionful Services
    
Let us see the example, what will happen when you use the one-way 
communication with Sessionful service.
    


    

        [ServiceContract(SessionMode = SessionMode.Required)]
    interface IMyContract
    {
        [OperationContract(IsOneWay = true)]
        void MyMethod();
    }
    

    
As per above configuration, when client makes one-way call using 
MyMethod() operation and if it close the proxy. Client will be blocked 
until operation completes. It will be good practice, that one-way 
operation should be applied on per-call and singleton service.
    

Suppose If you want to make use of One-way operation in Sessionful 
service, use in the last operation of the service which will terminate 
the session. This operation should not return any value.
    


    

        [ServiceContract(SessionMode = SessionMode.Required)]
    interface IMyContract
    {
        [OperationContract]
        void MyMethod1();

        [OperationContract]
        string MyMethod2();

        [OperationContract(IsOneWay = true, IsInitiating = false,
                                           IsTerminating = true)]
        string CloseSessionService(int id);
       
    }
    

    

    

    

    
One-Way Operations and Exceptions
    
Suppose when we are using BasicHttpBinding or WSHttpBinding,
 i.e. no transport session is used, if any exception throw by service 
will not affect the client. Client can make a call to the service using 
same proxy
    


    

    [ServiceContract]
interface IMyContract
{
   [OperationContract(IsOneWay = true)]
   void MethodWithError( );

   [OperationContract]
   void MethodWithoutError( );
}
//Client side without transport session
MyContractClient proxy = new MyContractClient( );
proxy.MethodWithError( ); //No exception is thrown from serivce
proxy.MethodWithoutError( ); //Operation will execute properly
proxy.Close( );
    

    

    

    
In the presence of transport session, any exception thrown by 
service will fault the client channel. Client will not be able to make 
new call using same proxy instance.
    


    

    //Client side transport session
MyContractClient proxy = new MyContractClient( );
proxy.MethodWithError( ); 
proxy.MethodWithoutError( ); //Can not executre because channel is faulted
    

    

    proxy.Close( );
    

     
    

    

    
Callback Service
    

    

    
Till now we have seen that the all clients will call the service
 to get the things done. But WCF also provides the service to call the 
client. In which, service will act as client and client will act as 
service.
    


      

    • HTTP protocols are connectionless nature, so it is not supported
 for callback operation. So BasicHttpBinding and WSHttpBinding cannot be
 used for this operation.
      • 

    • WCF support WSDualHttpBinding for call back operation.
      • 

    • All TCP and IPC protocols support Duplex communication. So all 
these binding will be used for callback operation.
      • 

    

    

    

    
Defining and configuring a callback contract
    
Callback service can be enabled by using CallbackContract 
property in the ServiceContract attribute. In the below example 
you can find the decalration of the callback contract and it is 
configured in the ServiceContract attribute.
    


    

        public interface IMyContractCallback
    {
        [OperationContract]
        void OnCallback();
    }
    [ServiceContract(CallbackContract = typeof(IMyContractCallback))]
    public interface IMyContract
    {
        [OperationContract()]
        void MyMethod();
    }
    

    


    

    

    
Client Callback Setup
    
As I said earlier, in callback operation client will act as service 
and service will act as client. So client has to expose a callback 
endpoint to the service to call. In the earlier part of the tutorial I 
have mention that InstanceContext is the execution scope of inner most 
service instance. It provides a constructor that takes the service 
instance to the host.
    

    

     IMyContractCallback callback=new MyCallback();
        InstanceContext cntx=new InstanceContext(callback);

        MyServiceClient proxy = new MyServiceClient(cntx);
        proxy.MyMethod();   
    

    
The client must use a proxy that will set up the bidirectional 
communication and pass the callback endpoint reference to the service. 
This can be achieved by creating the proxy using DuplexClientBase
    


    

       class MyServiceClient:DuplexClientBase,IMyContract
    {
        public MyServiceClient(InstanceContext callbackCntx)
            : base(callbackCntx)
        {            
        }
        public void MyMethod()
        {
             base.Channel.MyMethod();
        }
    }
    

    

    
Service-Side Callback Invocation
    

    
The client-side callback endpoint reference is passed along with 
every call the client makes to the service, and it is part of the 
incoming message. The OperationContext class provides the service with 
easy access to the callback reference via the generic method GetCallbackChannel<T>(
 ).
Service can call the client side callback method using reference e to 
the client side callback instance. The following code shows the callback
 method invocation.

    

    

    IMyContractCallback
 callbackInstance=OperationContext.Current.GetCallbackChannel();
            callbackInstance.OnCallback();
    

    

     
    

     
    

    

    
Events
    

    

    
Events allow the client or clients to be notified about 
something that has occurred on the service side. An event may result 
from a direct client call, or it may be the result of something the 
service monitors. The service firing the event is called the publisher, 
and the client receiving the event is called the subscriber.
    
 


      

    • Publisher will not care about order of invocation of subscriber.
 Subscriber can be executed in any   manner. 
      • 

    • Implementation of subscriber side should be short duration. Let 
us consider the scenario in which you what to publish large volume of 
event. Publisher will be blocked, when subscriber is queued on previous 
subscription of the event. These make publishers to put in wait state. 
It may lead Publisher event not to reach other subscriber.
      • 

    • Large number of subscribers to the event makes the accumulated 
processing time of each subscriber could exceed the publisher's timeout
      • 

    • Managing the list of subscribers and their preferences is a 
completely service-side implementation. It will not affect the client; 
publisher can even use .Net delegates to manage the list of subscribers.
      • 

    • Event should always one-Way operation and it should not return 
any value
      • 

    

    

    

    
Definition
    

    

        public interface IMyEvents
    {
        [OperationContract(IsOneWay = true)]
        void Event1();
    }
    

    
Let us understand more on Event operation by creating sample service
    


    

    
Step 1 : 
Create ClassLibrary project in the Visual Studio 2008 and name it as 
WCFEventService as shown below.
    



    

    
Step 2: 
Add reference System.ServiceModel to the project
    

Create the Event operation at the service and set IsOnwWay 
property to true. This operation should not return any value. Since 
service has to communicate to the client, we need to use CallbackContract
 for duplex communication. Here we are using one operation to subscribe 
the event and another for firing the event.
    


    

    public interface IMyEvents
    {
        [OperationContract(IsOneWay = true)]
        void Event1();
    }

   [ServiceContract(CallbackContract = typeof(IMyEvents))]
   public interface IMyContract
   {
       [OperationContract]
       void DoSomethingAndFireEvent();

       [OperationContract]
       void SubscribeEvent();

   }
    

    

    

    
Step 3: 
Implementation of the Service Contract is shown below.
    

In the Subscription operation, I am using Operationcontext to get the
 reference to the client instance and Subscription
 method is added as event handler to the service event.
DoSomethingAndFireEvent operation will fire the event as shown.
    

MyPublisher.cs

    

       [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
   public  class MyPublisher : IMyContract
    {
        static Action m_Event1 = delegate { };

        public void SubscribeEvent()
        {
            IMyEvents subscriber = OperationContext.Current.GetCallbackChannel();
            m_Event1 += subscriber.Event1;
        }

        public static void FireEvent()
        {
            m_Event1();
        }

        public void DoSomethingAndFireEvent()
        {
            MyPublisher.FireEvent();           
        }
    }
    

    

    

    
Step 4:
Create the Console application using Visual Studio 2008 and name it as 
WcfEventServiceHost. This application will be used to self-host the 
service.

    



    

    
Step 5:
Add System.ServiceModel and WcfEventService as reference 
to the project.
    


    

    static void Main(string[] args)
        {
            Uri httpUrl = new Uri("http://localhost:8090/MyPublisher/");
            ServiceHost host = new ServiceHost(typeof(WcfEventService.MyPublisher), httpUrl);
            host.Open();
            Console.WriteLine("Service is Hosted at {0}", DateTime.Now.ToString());
            Console.WriteLine("Host is running...Press  key to stop the service.");
            Console.ReadLine();
            host.Close();
        }
  
    

    

    

    
Step 6:
Use Duplex binding to support Callback operation.
    

Web.Config

    

    <system.serviceModel>
    <services >
      <service behaviorConfiguration="ServiceBehavior"  
      name="WcfEventService.MyPublisher">
        <endpoint address="http://localhost:8090/MyPublisher" 
        binding="wsDualHttpBinding" contract="WcfEventService.IMyContract">
          <identity>
            <dns value="localhost"/>
          </identity>
        </endpoint>
        <endpoint address="mex" binding="mexHttpBinding"
         contract="IMetadataExchange"/>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="ServiceBehavior">
          <serviceMetadata httpGetEnabled="true"/>
          <serviceDebug includeExceptionDetailInFaults="true "/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
    

    

    

    
Step7:
Run the host application as shown below.


    

    
Step 8:
Create the console application using visual studio and name it as WcfEventServiceClient
 as shown below. This application will act a client which is used to 
subscribe the event from service.
    



    

    
Step 9:
Create the proxy class as shown below. Use DuplexClientBase to 
create the proxy, because it will support bidirectional communication. 
Create the contractor which will accept InstanceContext as parameter.
    

EventServiceClient.cs

    

     class EventServiceClient:DuplexClientBase<IMyContract>,IMyContract 
    {
        public EventServiceClient(InstanceContext eventCntx)
            : base(eventCntx)
        {
            
        }

        public void  DoSomethingAndFireEvent()
        {
            base.Channel.DoSomethingAndFireEvent();
        }

        public void SubscribeEvent()
        {
            base.Channel.SubscribeEvent();
        }
      
    }
    

    

    

    
Step 10:
Implementation of IMyEvents at client side is shown below. This method 
will be called when service publish the event.
    


    

    class MySubscriber : IMyEvents
    {
       public void Event1()
        {
            Console.WriteLine("Event is subscribed from the 
            service at {0}",DateTime.Now.ToString() );
        }
  
    }
    

    

    

    
Step 11:
Main method of the client side you can find the creating Subscription 
instance and it passed to service using InstanceContext
    


    

     static void Main(string[] args)
        {
            IMyEvents evnt = new MySubscriber();
            InstanceContext evntCntx = new InstanceContext(evnt);

            EventServiceClient proxy = new EventServiceClient(evntCntx);
            Console.WriteLine("Client subscribe the event
             from the service at {0}",DateTime.Now.ToString());
            proxy.SubscribeEvent();
            Console.WriteLine("Client call operation which will fire the event");
            proxy.DoSomethingAndFireEvent();
            Console.ReadLine();
        }
    

    

    

    
Step 12:
Run the client application and you see the when event is fired from the 
service. Subscriber got notification.
    



    

    

    

    

    
Transfer mode
    

    
In our normal day today life, we need to transfer data from one 
location to other location. If data transfer is taking place through WCF
 service, message size will play major role in performance of the data 
transfer. Based on the size and other condition of the data transfer, 
WCF supports two modes for transferring messages
    


    

    
Buffer transfer
    
When the client and the service exchange messages, these messages are
 buffered on the receiving end and delivered only once the entire 
message has been received. This is true whether it is the client sending
 a message to the service or the service returning a message to the 
client. As a result, when the client calls the service, the service is 
invoked only after the client's message has been received in its 
entirety; likewise, the client is unblocked only once the returned 
message with the results of the invocation has been received in its 
entirety.
    

    

    
Stream transfer
    
When client and Service exchange message using Streaming transfer 
mode, receiver can start processing the message before it is completely 
delivered. Streamed transfers can improve the scalability of a service 
by eliminating the requirement for large memory buffers. If you want to 
transfer large message, streaming is the best method.
    

    

    
StreamRequest
    
In this mode of configuration, message send from client to service 
will be streamed
    

    

    
StreamRespone
    
In this mode of configuration, message send from service to client 
will be streamed.
    

    

    
Configuration
    

    

    <system.serviceModel>
    <services >
      <service behaviorConfiguration="ServiceBehavior"  name="MyService">
        <endpoint address="" binding="netTcpBinding"
         bindingConfiguration="MyService.netTcpBinding" contract="IMyService">
          <identity>
            <dns value="localhost"/>
          </identity>
        </endpoint>
        <endpoint address="mex" binding="mexHttpBinding" 
        contract="IMetadataExchange"/>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="ServiceBehavior">
          <serviceMetadata httpGetEnabled="true"/>
          <serviceDebug includeExceptionDetailInFaults="true "/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
    <bindings >
      <netTcpBinding>
        <binding name="MyService.netTcpBinding" 
        transferMode="Buffered" closeTimeout ="0:01:00" openTimeout="0:01:00"></binding>
      </netTcpBinding>
    </bindings>
  </system.serviceModel>
    

    

    

    
Differences between Buffered and Streamed Transfers
    

    

    
     Buffered
     Streamed
  
    

    
     Target can process the message once it is completely received.
     Target can start processing the data when it is partially 
received
  
    

    
     Performance will be good when message size is small
     Performance will be good when message size is larger(more than 
64K)
  
    

    
     Native channel shape is IDuplexSessionChannel
     Native channels are IRequestChannel and IReplyChannel
    

    

     
    

    

    

    

    

    

    
Streaming
    

    

    
Client and Service exchange message using Streaming transfer 
mode, receiver can start processing the message before it is completely 
delivered. Streamed transfers can improve the scalability of a service 
by eliminating the requirement for large memory buffers. If you want to 
transfer large message, streaming is the best method.
    
 

    
Supported Bindings
    

      

    • BasicHttpBinding
      • 

    • NetTcpBinding
      • 

    • NetNamedPipeBinding
      • 

    

    

    

    
Restrictions
    
There are some restriction, when streaming is enabled in WCF
    


      

    • Digital signatures for the message body cannot be performed 
      • 

    • Encryption depends on digital signatures to verify that the data
 has been reconstructed correctly. 
      • 

    • Reliable sessions must buffer sent messages on the client for 
redelivery if a message gets lost in transfer and must hold messages on 
the service before handing them to the service implementation to 
preserve message order in case messages are received out-of-sequence. 
      • 

    • Streaming is not available with the Message Queuing (MSMQ) 
transport
      • 

    • Streaming is also not available when using the Peer Channel 
transport
      • 

    

    

    

    
I/O Streams
    
WCF uses .Net stream class for Streaming the message. Stream in base 
class for streaming, all subclasses like FileStream,MemoryStream, 
NetworkStream are derived from it. Stream the data, you need to do is, 
to return or receive a Stream as an operation parameter.
    


    

    [ServiceContract]
public interface IMyService
{
    [OperationContract]
    void SaveStreamData(Stream emp);

    [OperationContract]
    Stream GetStreamData();

}
    

    
Note: 

      

    1. Stream and it's  subclass can be used for streaming, but it 
should be serializable
      2. 

    2. Stream and MemoryStream are serializable and it will support 
streaming
      3. 

    3. FileStream is non serializable, and it will not support 
streaming
      4. 

    

    

    


    
Streaming and Binding
    
Only the TCP, IPC, and basic HTTP bindings support streaming. With 
all of these bindings streaming is disabled by default. TransferMode
 property should be set according to the desired streaming mode in the 
bindings.
    


    

    public enum TransferMode
{
   Buffered, //Default
   Streamed,
   StreamedRequest,
   StreamedResponse
}
public class BasicHttpBinding : Binding,...
{
   public TransferMode TransferMode
   {get;set;}
   //More members
}
    

    

      

    • StreamedRequest - Send and accept requests in streaming 
mode, and accept and return responses in buffered mode
      • 

    • StreamResponse - Send and accept requests in buffered 
mode, and accept and return responses in streamed mode
      • 

    • Streamed - Send and receive requests and responses in 
streamed mode in both directions
      • 

    • Buffered -Send and receive requests and responses in 
Buffered mode in both directions
      • 

    

    

    

    
Streaming and Transport
    
The main aim of the Streaming transfer mode is to transfer large size
 data, but default message size is 64K. So you can increase the message 
size using maxReceivedMessageSize attribute in the binding 
element as shown below.
    


    

    <system.serviceModel>
    <bindings >
      <netTcpBinding>
        <binding name="MyService.netTcpBinding"
         transferMode="Buffered" maxReceivedMessageSize="1024000">
        </binding>
      </netTcpBinding>
    </bindings>
  </system.serviceModel>
    

    

    
Transaction
    

    
A transaction is a collection or group of one or more units of 
operation executed as a whole. It provides way to logically group single
 piece of work and execute them as a single unit. In addition, WCF 
allows client applications to create transactions and to propagate 
transactions across service boundaries.
    


    

    
Recovery Challenge
    
Let us discuss more on challenge we will phased and how to recover 
from it.
    


      

    1. Consider a system maintained in consistent state, when 
application fail to perform particular operation, you should recover 
from it and place the system in the consistent state.
      2. 

    2. While doing singe operation, there will be multiple atomic sub 
operation will happen. These operations might success or fail. We are 
not considering about sub operation which are failed. We mainly consider
 about the success operation. Because we have to recover all these state
 to its previous consistence state.
      3. 

    3. Productivity penalty has to be payee for all effort required for
 handcrafting the recovery logic
      4. 

    4. Performance will be decreased because you need to execute huge 
amount of code.
      5. 

    

    

    

    
Solution
    
Best way to maintain system consistence and handling error-recovery 
challenge is to use transactions.
Below figure gives idea about transaction.
    



      

    • Committed transaction: Transaction that execute 
successfully and transfer the system from consistence state A to B.
      • 

    • Aborted transaction: Transaction encounters an error and 
rollback to Consistence State A from intermediate state.
      • 

    • In-doubt transaction: Transactions fail to either in 
commit or abort.
      • 

    

    

    

    
Transaction Resources
    
Transactional programming requires working with a resource that is 
capable of participating in a transaction, and being able to commit or 
roll back the changes made during the transaction. Such resources have 
been around in one form or another for decades. Traditionally, you had 
to inform a resource that you would like to perform transactional work 
against it. This act is called enlisting. Some resources support 
auto-enlisting.
    

    

    
Transaction Properties 
    
Transaction can be said as pure and successful only if meets four 
characteristics.
    


      

    • Atomic - When transaction completes, all the individual changes 
made to the resource while process must be made as to they were all one 
atomic, indivisible operation. 
      • 

    • Consistent - transaction must leave the system in consistent 
state.
      • 

    • Isolated - Resources participating in the transaction should be 
locked and it should not be access by other third party. 
      • 

    • Durable - Durable transactions must survive failures.
      • 

    

    
 

    

    

    

    

    

    

    

     
    

    

     
    

    

    

    

    
 

    

    

    
 

    • 




















Posted by
Vamsi Krishna Reddy.Munnamgi


at
11:53 AM



















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11 comments:








  1. anuradhaApril 13, 2012 at 12:59 PM
    Hi vamsi,
            This post is excellent for me. i searched many blogs but your blog is ultimate.
     Thanks for this.
    ReplyDelete
  2. AnonymousAugust 24, 2012 at 8:57 PM
    Hi Vamsi. This is the best WCF tutorial I have ever read. Thanks so much!
    ReplyDelete
  3. AnonymousOctober 3, 2012 at 9:17 PM
    Hi Vamsi,I am still going through it,its pretty good.However for the iis hosting example you missed out to provide the binding name in the constructor of the proxy class and to add the contents of the output.config file to the app.config file.
    ReplyDelete
  4. UnknownFebruary 3, 2013 at 12:24 AM
    Good one complete tutorial with good presentation Thanks Vams !....................
    ReplyDelete
  5. AnonymousMarch 21, 2013 at 10:59 PM
    Hi... Your post is by far the most exhaustive that I have seen. It encompasses material enough for a ebook. Everything is so easily explained and implemented.

    You are the best....

    Abhishek
    ReplyDelete
  6. AnonymousApril 10, 2013 at 5:02 PM
    its best tutorial... thanks
    ReplyDelete
  7. TijoJanuary 7, 2014 at 2:22 PM
    A complete reference for WCF beginers...Thanks a lot.
    It helped me a lot
    (softsprogrammer.blogspot.in)
    ReplyDelete
  8. AnonymousFebruary 13, 2014 at 4:50 PM
    Awesome tutorial...thanks for sharing...
    ReplyDelete
  9. AnonymousFebruary 19, 2015 at 1:20 AM
    go to youtube..search for 'KUDVENKAT WCF SERIES'...you wont regret
    ReplyDelete
  10. AnonymousJanuary 27, 2016 at 4:36 PM
    Good article and required information only. thank you for blog...
    Nilesh
    ReplyDelete


































        

      









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