How to define the default action of a form?

[Hailong Zhang]

I have a search bar contains a TextBox and a CommandLink. When user hit "Enter" in the TextBox, I don't know what happens, it seems that it refresh the page. Instead, I want to submit the form when "Enter" is hit, behave the same as use click the CommandLink.
I have tried "j4j Tag Library, defaultAction", but it doesn't work.

Any solutions?

Thanks in advance.

Regards,
Toby