title: Get selected date from calendarextender
body: <p>I have a textbox extended with the calendar extender in ASP.NET Ajax. If I get the selected date of the calendar, the variable is null, and the text of the textbox always defaults to the value I specified (Default) for when the page loads.</p>
  
  <p>How can I get the selected date when I change it? I need this for the button click event handler.</p>
  
  <p>Thanks</p>