title: How to validate a calculated column on an ADO.NET DataTable
body: <p>According to MS, calculated columns (AKA expression columns) don't raise any DataTable events: </p>
  
  <p><a href="http://msdn.microsoft.com/en-us/library/w9y9a401%28v=vs.80%29.aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/w9y9a401%28v=vs.80%29.aspx</a>, </p>
  
  <p>This makes it impossible to use the DataTable.ColumnChanging event to validate the value of such column by using the technique documented at:</p>
  
  <p><a href="http://msdn.microsoft.com/en-us/library/ms171930%28v=vs.80%29.aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/ms171930%28v=vs.80%29.aspx</a> </p>
  
  <p>I'd like to know if someone has thought of a way to add some form of validation to such calculated columns so that it will work with the standard ErrorProvider control on a Windows Form ?</p>
  
  <p>Thank you</p>