you cannot check the key char until tthe key is pressed and when any key is pressed a keyevent is fired..
and this depends on you that which event u want to fire either event on pressing or after pressing or after key is up and so on..

so u only need is in event is the args as (object sender, KeyEventArgs e)
now u have different properties with 'e' and using intellisence check whether there is keychar prop so u write as follows..
if(e.keychar<64 && e.keychar>91) to check if Capitol alphabet is pressed(i.e caps +alphabet) and so on..
e.keychar returns ascii values of key pressed

Check and do tel me how it runs.. m waiting