In gridview how to use rowcommand event for a button

I am using a gridview in aspx and i have two pages that registration and details.aspx once registration completed it should goto details page in details.aspx i have kept a gridview in that GV i am supposed be use row command event for a button it should show the all the rsults for the students with the edit button as the last column for all the students i used item template for that. but in row command event i dont know the function to write if user clicking edit it should goto the edit page using the userid the id should be noon editable mode and other fields can editable.

How to detect which button was clicked in code behind?

I have three buttons each calling btn_Clicked on their onClick event. In code behind I want to get the ID of the button that caused postback. I know I can assign each button to call a different method but I would like to learn a bit of ASP.Net. Also tell me which method is more efficient? Calling different methods on different button clicks or calling the same method (if the functionality of each button is same).