 <p><code>DateTime</code> is a value type object which mean that you cannot set it's value to <code>null</code>.</p> <p>Use the <code>DBNull.Value</code> to assign the data. </p> <hr> <p><a href="http://msdn.microsoft.com/en-us/library/s1ax56ch.aspx" rel="nofollow">Value Types</a></p>