what is ispostback in asp.net

Postback in an event that is triggered when a action is performed by a contol on a asp.net page. for eg. when you click on a button the data on the page is posted back to the server for processing.

Is Postback is normally used on page _load event to detect if the page is getting generated due to postback requested by a control on the page or if the page is getting loaded for the first time.

For Example:

if(!IsPostBack)//also you can write IsPostBack==false

{

//It means your page has loaded first time.

}

if(IsPostBack)//also you can write IsPostBack==true

{

//It means your page has submitted.

}

See below link for more details:

http://msdn.microsoft.com/en-us/library/aa720472(v=vs.71).aspx