What is isPostback?

Postback is a way to send information from the client  to the server and after processing it back to the client. So sometimes in our project we need to check whether the page loading is done by the user action(for eg. Button  click) or it is an initial loading of the page. To check this we have a property of the page called isPostback property.

It is mainly used in pageloads to check whether the page loading is done by the initial request or not. 

Let  us look one example to make this more clear.

For example, if we want to  display a name as "guest" in a label on the initial loading of the page and then take a username from the user and display it in that label.

To do this we need to keep in mind that we need the name "guest" only when the page is first loaded and after the button  click we need to show the name of the user that is entered in the textbox.

Design

Code Behind

Output

On initial load:

After entering my name and clicking the display button: