void VersionIdentifierControl_Validating(object sender, CancelEventArgs e)
{
string saved = null;
if( _versionIdentifier != null )
saved = XmlUtils.SerializeObject( _versionIdentifier );
ControlsToData();
ValidateToSchema(_versionIdentifier);
if (saved == null)
_versionIdentifier = null;
else
_versionIdentifier = (VersionIdentifier)XmlUtils.DeserializeObject(_versionIdentifier, saved);
}