// Update Content of GridViewColumnHeader
 private void UpdateHeaderContent(GridViewColumnHeader header)
 {
     if (header != null && header.IsInternalGenerated)
     {
         GridViewColumn column = header.Column;
         if (column != null)
         {
             if (column.Header == null)
             {
                 header.ClearValue(ContentControl.ContentProperty);
             }
             else
             {
                 header.Content = column.Header;
             }
         }
     }
 }