Perform action when user presses <Enter> on keyboard.

[token]

Okay, i found the solution, by searching the internet.
Simply put this line of code in your OnLoad event in your code-behind:

Page.RegisterHiddenField("__EVENTTARGET", "btnSearch")

and voila it works.

Thanks again everyone for helping me out.

Here is the page i found the solution on:
http://www.developer.com/net/asp/article.php/1594521