TreeList.BeforeDragNode Event
Fires when an attempt to drag a node is performed.
Namespace: DevExpress.XtraTreeList
Assembly: DevExpress.XtraTreeList.v24.2.dll
Declaration
Event Data
The BeforeDragNode event's data class is BeforeDragNodeEventArgs. The following properties provide information specific to this event:
| Property | Description |
|---|---|
| CanDrag | Gets or sets a value indicating whether a Tree List node can be dragged. |
| Node | Gets the current Tree List node. Inherited from NodeEventArgs. |
| Nodes | Gets the list of nodes that are about to be dragged. |
| PreviewImage | Gets or sets the image displayed near the mouse cursor during a drag-and-drop operation. |
Remarks
Node drag-and-drop can be enabled with the TreeListOptionsDragAndDrop.DragNodesMode setting. The result of drag and drop operations performed over nodes is specified by the TreeListOptionsBehavior.AutoChangeParent and TreeListOptionsDragAndDrop.CanCloneNodesOnDrop options.
Each time an attempt to drag a node is made, the BeforeDragNode event fires. You can use this event to specify whether the node can be dragged. The BeforeDragNodeEventArgs.CanDrag event’s parameter must be set to false to prohibit node dragging. The node which is about to be dragged can be identified via the NodeEventArgs.Node parameter.
You may also want to perform specific actions each time a drag and drop operation has been canceled or successfully finished. This can be performed using the TreeList.AfterDragNode and TreeList.DragCancelNode events respectively.
Example
The following sample code prohibits parent node dragging. The TreeList.BeforeDragNode event is handled for this purpose. The TreeListNode.HasChildren property is used to identify whether the currently processed node has child nodes.
using DevExpress.XtraTreeList;
private void treeList1_BeforeDragNode(object sender, BeforeDragNodeEventArgs e) {
if (e.Node.HasChildren) e.CanDrag = false;
}