title: Validating a textbox with AJAX Toolkit in ASP.NET
body: <p>I'm not really sure where or what to search for regarding the following question:</p>
  
  <p>I have a TextBox control and a Label control on my page. I have a database query ready and I would like to run it on the TextBox textchanged event in order to display a "valid" or "not valid" text in the Label.</p>
  
  <p>How can I achieve this without posting back the entire page on each textchanged event? I have installed the AJAX Control Toolkit and got the samples working but I don't seem to find an extender that would fit the bill. Any tips? Much appreciated, thank you.</p>