title: DatePicker control WP7
body: <p>I am using the DatePicker control from WP7 control toolkit in my app for the user to enter in an expiration date.  One of the scenarios is that the record doesn't have an expiration date.  How can I use the control such that by default, there is no date specified in the control and the user can select a different date?</p>
  
  <p>Also, if I user sets an expiration date but letter wants to clear it, I need to enable that as well.</p>
  
  <p>Pratik</p>