Answer:   IsPostBack is a property of the asp.net page that tells whether or not the page is on its initial load or if a user has perform a button click on your web page that has caused the page to post back to itself.

We use Not Ispostback to check if it is not a postback but the initial loading if the asp.net page. If page postback property is true then page is being post back and if property is false then page is not postback.

Answer:   IsPostBack is the property of the web Page class which is used to determine whether the page is posted back from the client. Whenever we don’t want to execute the code within the load event, then the page load event fires then we will use (! IsPostBack).