private void TabControlExt_TabOrderChanged(object sender, Syncfusion.Windows.Tools.Controls.TabOrderChangedEventArgs e)
 {
     var drag_Drop_Item = e.TargetItem;
     var oldIndex       = e.OldIndex;
     var newIndex       = e.NewIndex;
 }
 private void dockingmanager1_TabOrderChanged(object sender, Syncfusion.Windows.Tools.Controls.TabOrderChangedEventArgs e)
 {
     var dragged_Item = e.TargetItem;
     var oldIndex     = e.OldIndex;
     var newIndex     = e.NewIndex;
 }