event is raised when a row's Update button is clicked, but before the Grid View control updates the row.
This enables you to provide an event-handling method that performs a custom routine, such as canceling the update operation, whenever this event occurs.
You need to include the Grid View Command Field column to add Edit, Update and Cancel Buttons in the Grid View. You need to include Template Field for every column you want to provide Editing because Template Field provides you both Item Template and Edit Item Template to create interface for two separate Grid View modes. You need to handle Grid View events such as Row Editing, Row Canceling Edit and Row Updating to provide desired editing functionality.
Now I will show you the C# code behind file of the above ASP.
Take a look at the page load if you are binding on post back then the values get updated before you are able to access them.