Using TextChange event and asp.net ajax

Question

i am new to asp.net . i want to update a datagridview which is placed int updatepanel. i want to write some text in a TextBox and want to populate the datagridview just like a
"keyword search". on every TextChange Event i want to update the datagridview .

i dont know how to do that.

advance thanks for help provided.

mansoor.