you can get the button name with request.forms collection 
in the page load.

try 2 remember which button u had clicked. again select 
that button, go its property window by just right click on 
that button. n u get its name. which r unique.ok.

for that purpose they give the option is the tooltip that is
the shows the button name when you put the curser on the
button and also they might wrote the name of the button name.

due to the question i have one doubt?
The click event is done while i creating the web 
application time or after the deployment?

do a Response.write(sender.toString()) inside each of the 
click event methods

Just write code on page load

Response.Write(Request.Form[1].ToString());

u got button name which one u clicked.

Useing commandName property we can find out.

Just write code on page load and ur getting a control name
which one u clicked

string ctrlname = Page.Request.Params["__EVENTTARGET"];

the above code was returning the hidden field value. which 
will be non readble format.please make sure before entering 
the answer will it work or not.

i have two button btnadd and btnupdate
If (Array.IndexOf(Request.Form.AllKeys, btnadd.ClientID)) 
{
}