How to Disable the Submit Button

If you want to prevent multiple clicks on a form submit button, disable the button.

It’s easy, simple. I’ll show you exactly how to do it.

Simply add the in the page load but in this the server isde code is not excuted

b1.Attributes.Add(

other wise try like this
<input

   type="submit"

   onclick="this.disabled=true;">
"onclick", "this.disabled=true;");