Hi,guys, I am trying to use a button to check whether the register name is already registered or not , without submitting the whole form.

Now I have a problem: I use useSubmitBehavior and postbackUrl, so it firstly validate all other elements in the form , and I use requiredField in all other elements, so it need complete the form firstly , which doesn't meet my requirement , what can I do?
any sample code?

You can set a certain button to not perform complete form validation by setting the CausesValidation attribute to false.

-Peter

yes, thank you, now I have already solved this problem