how to use key events in asp.net

You need to underestand the event handling technique in ASP.Net.
Events are handled on the server side - see http://msdn.microsoft.com/en-us/library/6w2tb12s(v=VS.100).aspx[^] on how to add events to your code.

In case you need client side events, you need to add events to the scripting language you are using on the client side.