TreeViewControl.StartRecordDrag Event

Occurs when a drag-and-drop operation is started.

Assembly : DevExpress.Xpf.Grid.v25.2.dll

NuGet Package : DevExpress.Wpf.Grid.Core

Declaration

C#
VB.NET

csharp

public event EventHandler<StartRecordDragEventArgs> StartRecordDrag

Public Event StartRecordDrag As EventHandler(Of StartRecordDragEventArgs)

Event Data

The StartRecordDrag event's data class is StartRecordDragEventArgs. The following properties provide information specific to this event:

Property	Description
AllowDrag	Gets or sets whether an end-user can drag records.
AllowedEffects	Gets a member of the DragDropEffects enumeration that specifies which operations are allowed by the originator of the drag event.
Data	Gets or sets a data object that contains the data associated with the DataViewBase.StartRecordDrag event.
DragElement	Gets a drag element that is a control on which the drag-and-drop operation has been initiated.
Handled	Gets or sets a value that indicates the present state of the event handling for a routed event as it travels the route. Inherited from RoutedEventArgs.
OriginalSource	Gets the original reporting source as determined by pure hit testing, before any possible Source adjustment by a parent class. Inherited from RoutedEventArgs.
Records	Gets dragged records.
RoutedEvent	Gets or sets the RoutedEvent associated with this RoutedEventArgs instance. Inherited from RoutedEventArgs.
Source	Gets or sets a reference to the object that raised the event. Inherited from RoutedEventArgs.

The event data class exposes the following methods:

Method	Description
InvokeEventHandler(Delegate, Object)	When overridden in a derived class, provides a way to invoke event handlers in a type-specific way, which can increase efficiency over the base implementation. Inherited from RoutedEventArgs.
OnSetSource(Object)	When overridden in a derived class, provides a notification callback entry point whenever the value of the Source property of an instance changes. Inherited from RoutedEventArgs.

Remarks

You can use the StartRecordDrag event to cancel a drag operation.

The following code sample allows users to drag only records that do not have children:

XAML

xaml

<dxg:TreeViewControl x:Name="treeview"
                     AllowDragDrop="True"
                     StartRecordDrag="treeview_StartRecordDrag"/>

C#
VB.NET

csharp

void treeview_StartRecordDrag(object sender, DevExpress.Xpf.Core.StartRecordDragEventArgs e) {
    foreach (Employee employee in e.Records)
        e.AllowDrag = !treeview.GetNodeByValue(employee.Name).HasChildren;
    e.Handled = true;
}

Private Sub treeview_StartRecordDrag(ByVal sender As Object, ByVal e As DevExpress.Xpf.Core.StartRecordDragEventArgs)
    For Each employee As Employee In e.Records
        e.AllowDrag = Not treeview.GetNodeByValue(employee.Name).HasChildren
    Next

    e.Handled = True
End Sub

For information about drag-and-drop operations, refer to the following DevExpress WPF Grid help topic: Drag-and-Drop.