a question about Asp.net and Ajax?

[forde f]

There is a TextBox, if a user type his username , when he press the "Tab " or the cursor leave the TextBox , connect the SQlServer, find whether the username exists or not,if it exists ,then tell to the user,how do i come true by VB.net

[ajthepoolman]

I don't have the code in front of me here, but we do something similar with a sign in/out board. I can tell you to look up Update Panels in Yahoo and see if there is anything to guide you along.