In my ASP.Net web application, there is a textbox .When the user enters data  and moves to the next textbox, I want to validate the data against a table and if matching record is found, I want to display details in different controls  else I want to display a message and continue. I do not want to do the verification AFTER the user enters all data and press the Save button, but it should be done immediately. I was hoping that the Web Form textbox would have a LostFocus event, but do not know how to handle the requirement.