title: How to call a server side function on Leave event of a ASP.Net TextBox
body: <p>I am building a user registration form in asp.net. I want to check if the username is available or not on the leave event of the TextBox. I am not able to get the Leave Event of the TextBox.</p>
  
  <p>Should I use OnBlur event of the Html TextBox.
  Please Help.</p>