Drag And Drop Behavior

• Jan 23, 2019
• 4 minutes to read

The Drag and Drop Behavior allows you to add support for drag-and-drop operations between supported controls.

Supported controls

• GridControl (GridView)
• TreeList
• ListBoxControl

Behavior options

• Target—specifies the control to which the behavior is attached;
• PreviewVisible—specifies whether a preview of item(s) being dragged is displayed during operation;
• InsertIndicatorVisible—specifies whether the indicator is showing items’ insertion position;
• AllowDrop—specifies whether the attached control allows an end-user to drop the item(s) on it.

The code below shows how to assign a Drag and Drop Behavior to a control using the BehaviorManager.Attach method and specify its options.

C#

using DevExpress.Utils.DragDrop;

behaviorManager1.Attach<DragDropBehavior>(gridView1, behavior => {
    behavior.Properties.AllowDrop = true;
    behavior.Properties.InsertIndicatorVisible = true;
    behavior.Properties.PreviewVisible = true;
});

behaviorManager1.Attach<DragDropBehavior>(gridView2, behavior => {
    behavior.Properties.AllowDrop = false;
    behavior.Properties.InsertIndicatorVisible = false;
    behavior.Properties.PreviewVisible = false;
});

VB.NET

Imports DevExpress.Utils.DragDrop

behaviorManager1.Attach(Of DragDropBehavior)(gridView1, Sub(behavior)
    behavior.Properties.AllowDrop = True
    behavior.Properties.InsertIndicatorVisible = True
    behavior.Properties.PreviewVisible = True
End Sub)

behaviorManager1.Attach(Of DragDropBehavior)(gridView2, Sub(behavior)
    behavior.Properties.AllowDrop = False
    behavior.Properties.InsertIndicatorVisible = False
    behavior.Properties.PreviewVisible = False
End Sub)

Note

Drag and Drop Behaviors should be attached to the source and target controls to work correctly. Disable the source control’s AllowDrop setting to allow data to be transferred one way only.

Note

For a grid control with master-detail data presentation, attach a Drag and Drop Behavior to the main view (see GridControl.MainView).

Important

Business objects must have a default constructor with no parameters if the behavior is attached to data-aware controls that store these objects defined in code. Otherwise, rows that display these objects cannot be moved between controls.

Behavior events

• BeginDragDrop—occurs when a drag-and-drop operation starts allowing you to cancel the operation, or provide a custom preview image;
• DragEnter—occurs when an object is dragged into the control’s bounds;
• DragOver—occurs when an object is dragged over the control’s bounds;
• DragLeave—occurs when an object is dragged out of the control’s bounds;
• DragDrop—occurs when a drag-and-drop operation is completed;
• EndDragDrop—allows you to perform custom actions after a drag-and-drop operation is completed.

A DragDropEvents component is automatically added to your form when you attach a Drag and Drop Behavior to a control at design time. You can use this component to subscribe to the behavior’s events.

C#

dragDropEvents1.DragDrop += dragDropEvents1_DragDrop;
dragDropEvents1.DragOver += dragDropEvents1_DragOver;

VB.NET

AddHandler dragDropEvents1.DragDrop, AddressOf dragDropEvents1_DragDrop
AddHandler dragDropEvents1.DragOver, AddressOf dragDropEvents1_DragOver

When handling the drag and drop events for a grid view, use the following static (Shared in VB) methods to calculate GridView-specific arguments:

• DragOverGridEventArgs.GetDragOverGridEventArgs—for the DragOver event;
• DragDropGridEventArgs.GetDragDropGridEventArgs—for the DragDrop event.

C#

using DevExpress.Utils.DragDrop;
using DevExpress.XtraGrid.Views.Grid;

dragDropEvents1.DragOver += Behavior_DragOver;
private void Behavior_DragOver(object sender, DragOverEventArgs e) {
    DragOverGridEventArgs args = DragOverGridEventArgs.GetDragOverGridEventArgs(e);
    //You can also cast DragOverEventArgs to DragOverGridEventArgs.
    //DragOverGridEventArgs args = (DragOverGridEventArgs)e;
}

dragDropEvents1.DragDrop += Behavior_DragDrop;
private void Behavior_DragDrop(object sender, DragDropEventArgs e) {
    DragDropGridEventArgs args = DragDropGridEventArgs.GetDragDropGridEventArgs(e);
    //You can also cast DragDropEventArgs to DragDropGridEventArgs.
    //DragDropGridEventArgs args = (DragDropGridEventArgs)e;
}

VB.NET

Imports DevExpress.Utils.DragDrop
Imports DevExpress.XtraGrid.Views.Grid

AddHandler dragDropEvents1.DragOver, AddressOf Behavior_DragOver
Private Sub Behavior_DragOver(ByVal sender As Object, ByVal e As DragOverEventArgs)
    Dim args As DragOverGridEventArgs = DragOverGridEventArgs.GetDragOverGridEventArgs(e)
    'You can also cast DragOverEventArgs to DragOverGridEventArgs.
    'Dim args As DragOverGridEventArgs = CType(e, DragOverGridEventArgs)
End Sub

AddHandler DragDropEvents1.DragDrop, AddressOf Behavior_DragDrop
Private Sub Behavior_DragDrop(ByVal sender As Object, ByVal e As DragDropEventArgs)
    Dim args As DragDropGridEventArgs = DragDropGridEventArgs.GetDragDropGridEventArgs(e)
    'You can also cast DragDropEventArgs to DragDropGridEventArgs.
    'Dim args As DragDropGridEventArgs = CType(e, DragDropGridEventArgs)
End Sub

When handling the drag-and-drop events for a tree list, use the Default method to calculate TreeList-specific arguments.

C#

dragDropEvents1.DragOver += DragDropEvents1_DragOver;

private void DragDropEvents1_DragOver(object sender, DevExpress.Utils.DragDrop.DragOverEventArgs e) {
    e.Default();
    if (e.InsertType != DevExpress.Utils.DragDrop.InsertType.AsChild){
        e.Action = DevExpress.Utils.DragDrop.DragDropActions.None;
        e.InsertType = DevExpress.Utils.DragDrop.InsertType.None;
    }
    else {
        e.Action = DevExpress.Utils.DragDrop.DragDropActions.All;
    }
    e.Handled = true;
}

VB.NET

Private Sub DragDropEvents1_DragOver(sender As Object, e As DragOverEventArgs) Handles DragDropEvents1.DragOver
    e.Default()
    If e.InsertType <> DevExpress.Utils.DragDrop.InsertType.AsChild Then
        e.Action = DevExpress.Utils.DragDrop.DragDropActions.None
        e.InsertType = DevExpress.Utils.DragDrop.InsertType.None
    Else
        e.Action = DevExpress.Utils.DragDrop.DragDropActions.All
    End If
    e.Handled = True
End Sub

Note

The Handled event argument should be set to true for event handlers to be in effect.