//
// OnDragLeave event handler. Updates the dragged node's ghost image's position.
//
protected override void OnDragLeave(EventArgs e)
{
base.OnDragLeave(e);
DragHelper.ImageList_DragLeave(Handle);
// Disable timer for scrolling dragged item
_timer.Enabled = false;
}
//
// OnDragDrop event handler. Ends a node dragging
//
protected override void OnDragDrop(DragEventArgs drgevent)
{
base.OnDragDrop(drgevent);
// Cancel if no node is being dragged
if (_draggedNode == null)
{
return;
}
// Unlock updates
DragHelper.ImageList_DragLeave(Handle);
if (drgevent.Effect == DragDropEffects.None)
{
// Set drag node and temp drop node to null
_draggedNode = null;
_tempDropNode = null;
// Disable scroll timer
_timer.Enabled = false;
return;
}
// Get drop node
TreeNode dropNode = GetNodeAt(PointToClient(new Point(drgevent.X, drgevent.Y)));
// Launch the feedback for the drag operation
TreeViewNodeDragEventArgs evArgs = new TreeViewNodeDragEventArgs(TreeViewNodeDragEventType.DragEnd, TreeViewNodeDragEventBehavior.PlaceInside, _draggedNode, dropNode);
if (DragOperation != null)
{
DragOperation(evArgs);
// Cancel the operation if the user specified so
if (evArgs.Cancel)
{
return;
}
}
// If drop node isn't equal to drag node, add drag node as child of drop node
if (_draggedNode != dropNode)
{
// Remove drag node from parent
if (_draggedNode.Parent == null)
{
Nodes.Remove(_draggedNode);
}
else
{
_draggedNode.Parent.Nodes.Remove(_draggedNode);
}
// Place the dragged node before or after the target node depending on mouse position
if (evArgs.EventBehavior == TreeViewNodeDragEventBehavior.PlaceBeforeOrAfterAuto)
{
// Get drop node
Point mouseP = PointToClient(MousePosition);
// Figure out whether the node should be added uder or over the pointed item by checking if the mouse is under or over the middle of the item
evArgs.EventBehavior = mouseP.Y > dropNode.Bounds.Y + dropNode.Bounds.Height / 2
? TreeViewNodeDragEventBehavior.PlaceAfter
: TreeViewNodeDragEventBehavior.PlaceBefore;
}
// Place the dragged node before the target node
if (evArgs.EventBehavior == TreeViewNodeDragEventBehavior.PlaceBefore)
{
// Add drag node before drop node
if (dropNode.Parent != null)
{
dropNode.Parent.Nodes.Insert(dropNode.Index, _draggedNode);
}
else
{
Nodes.Insert(dropNode.Index, _draggedNode);
}
SelectedNode = _draggedNode;
}
// Place the dragged node after the target node
if (evArgs.EventBehavior == TreeViewNodeDragEventBehavior.PlaceAfter)
{
// Add drag node after drop node
if (dropNode.Parent != null)
{
dropNode.Parent.Nodes.Insert(dropNode.Index + 1, _draggedNode);
}
else
{
Nodes.Insert(dropNode.Index + 1, _draggedNode);
}
SelectedNode = _draggedNode;
}
// Place the dragged node inside the target node
if (evArgs.EventBehavior == TreeViewNodeDragEventBehavior.PlaceInside)
{
// Add drag node to drop node
dropNode.Nodes.Add(_draggedNode);
dropNode.ExpandAll();
}
// Launch the feedback for the drag operation
evArgs = new TreeViewNodeDragEventArgs(TreeViewNodeDragEventType.AfterDragEnd, evArgs.EventBehavior, _draggedNode, dropNode);
DragOperation?.Invoke(evArgs);
// Set drag node and temp drop node to null
_draggedNode = null;
_tempDropNode = null;
// Disable scroll timer
_timer.Enabled = false;
}
}
