title: Databinding textbox can't exit
body: <p>I have the same issue as <a href="https://stackoverflow.com/questions/217912/data-bound-textbox-cant-exit">this post</a>. It is caused bij a numeric nullable value of my dataset object. When the property of this object has an initial value of null, I can exit my textbox. When my textbox has a initial numeric value and clear the textbox, I cannot exit.</p>
  
  <p>I want to be able to supply a null value by clearing the textbox. I know this is a validating issue, when setting the "CausesValidating" property to false, I can exit. Also my property setting function is never reached.</p>
  
  <p>Any ideas or suggestions? Many thanks in advance!</p>