System.Windows.Forms.CustomTabControl.StartDragDrop C# (CSharp) Method

        private void StartDragDrop()
        {
            if (!this._dragStartPosition.IsEmpty){
              			    TabPage dragTab = this.SelectedTab;
              			    if (dragTab != null){
              			    	//	Test for movement greater than the drag activation trigger area
              				    Rectangle dragTestRect = new Rectangle(this._dragStartPosition, Size.Empty);
              				    dragTestRect.Inflate(SystemInformation.DragSize);
              				    Point pt = this.PointToClient(Control.MousePosition);
              				    if (!dragTestRect.Contains(pt)){
              			            this.DoDragDrop(dragTab, DragDropEffects.All);
              					    this._dragStartPosition = Point.Empty;
              				    }
              			    }
              			}
        }