ClearCanvas.Desktop.View.WinForms.BindingTreeView.OnDragOver C# (CSharp) Method

        protected override void OnDragOver(DragEventArgs e)
        {
            // determine the node under the cursor
			Point cursor = _treeCtrl.PointToClient(new Point(e.X, e.Y));
            BindingTreeNode node = (BindingTreeNode)_treeCtrl.GetNodeAt(cursor);
 
            // determine what effect the user is trying to accomplish
            DragDropEffects desiredEffect = GetDragDropDesiredEffect(e);

			// determine if the user is trying to drag to the top, middle or bottom areas of the node
        	DragDropPosition position = DragDropPosition.Default;
        	if (this.AllowDropToIndex && node != null)
        	{
        		float result = 1f*(cursor.Y - node.Bounds.Y)/node.Bounds.Height;
        		if (result <= 0.2f)
        			position = DragDropPosition.Before;
        		else if (result >= 0.8f)
        			position = DragDropPosition.After;
        	}

            // optimization: only care if different than the last known drop-target node, or different desired effect, or different drop position
        	if (node != _dropTargetNode || desiredEffect != _dropEffect || position != _dropPosition)
            {
                _treeCtrl.BeginUpdate();    // suspend drawing

                // un-highlight the last known drop-target node
				HighlightNode(_dropTargetNode, false);
				SetInsertMark(_dropTargetNode, DragDropPosition.Default);

                // set the drop target node to this node
                _dropTargetNode = node;
                _dropEffect = desiredEffect;
				_dropPosition = position;

                // check if drop target node exists and what kind of operation it will accept
                DragDropKind acceptableKind = (_dropTargetNode == null) ?
                    DragDropKind.None : _dropTargetNode.CanAcceptDrop(GetDragDropData(e), GetDragDropKind(desiredEffect), _dropPosition);

                // display the appropriate effect cue based on the result
                e.Effect = GetDragDropEffect(acceptableKind);

                // if the drop target is valid and willing to accept data, highlight it
                if (acceptableKind != DragDropKind.None)
                {
					HighlightNode(_dropTargetNode, _dropPosition == DragDropPosition.Default);
					SetInsertMark(_dropTargetNode, _dropPosition);
                }

                _treeCtrl.EndUpdate(); // resume drawing
            }

			// perform drag scrolling
			if (_treeCtrl.ClientRectangle.Contains(cursor))
			{
				if (cursor.Y > _treeCtrl.Height - _treeCtrl.ItemHeight/2)
					SendMessage(_treeCtrl.Handle, (int) WindowsMessages.WM_VSCROLL, new IntPtr(1), IntPtr.Zero);
				else if (cursor.Y < _treeCtrl.ItemHeight/2)
					SendMessage(_treeCtrl.Handle, (int) WindowsMessages.WM_VSCROLL, IntPtr.Zero, IntPtr.Zero);
			}
            
            base.OnDragOver(e);
        }