Difference between ref and out parameters

Here I will explain difference between ref and out parameters in c#.net with example.

 Both ref and out parameters are used to pass arguments within a method. 
These ref and out parameters are useful whenever your method wants to return more than one value. 
Regarding ref parameter you need to initialize it before passing to the method and out parameter you don’t need to initialize before passing to function.    

Ref Parameter

If you want to pass a variable as ref parameter you need to initialize it before you pass it as ref parameter to method. Ref keyword will pass parameter as a reference this means when the value of parameter is changed in called method it get reflected in calling method also.

Declaration of Ref Parameter

Generally we will use ref parameters like as shown below

int i=3; // variable need to be initialized

Refsample(ref i);


If you observe above code first we declared variable and initialized with value 3 before it pass a ref parameter to Refsample method

Example
 

class Program

{

static void Main()

{

int i; // variable need to be initialized

i = 3;

Refsample(ref i);

Console.WriteLine(i);

}

public static void Refsample(ref int val1)

{

val1 += 10;

}

}

When we run above code we will get like as shown below

Output

*********Output************

13

*********Output************

As we discussed if ref parameter value changed in called method that parameter value reflected in calling method also

Out Parameter

If you want to pass a variable as out parameter you don’t need to initialize it before you pass it as out parameter to method. Out keyword also will pass parameter as a reference but here out parameter must be initialized in called method before it return value to calling method.

Declaration of Out Parameter

Generally we will use out parameters like as shown below

int i,j; // No need to initialize variable

Outsample(out i, out j);



If you observe above code first we declared variable and we it pass a out parameter to Outsample method without initialize the values to variables



Example

class Program

{

static void Main()

{

int i,j; // No need to initialize variable

Outsample(out i, out j);

Console.WriteLine(i);

Console.WriteLine(j);

}

public static int Outsample(out int val1, out int val2)

{

val1 = 5;

val2 = 10;

return 0;

}

}

If we observe code we implemented as per our discussion like out parameter values must be initialized in called method before it return values to calling method

When we run above code we will get like as shown below


Output

5

10

using System;

class Program
{
    static void Main()
    {
 int val = 0;

 Example1(val);
 Console.WriteLine(val); // Still 0!

 Example2(ref val);
 Console.WriteLine(val); // Now 2!

 Example3(out val);
 Console.WriteLine(val); // Now 3!
    }

    static void Example1(int value)
    {
 value = 1;
    }

    static void Example2(ref int value)
    {
 value = 2;
    }

    static void Example3(out int value)
    {
 value = 3;
    }
}

Output

0
2
3