DragEnter Attached Event

DragDrop.DragEnter Attached Event

 

Occurs when an object is dragged into the bounds of an element that is acting as a drop target.

Namespace:   System.Windows
Assembly:  PresentationCore (in PresentationCore.dll)

See AddDragEnterHandler, RemoveDragEnterHandler

This event is raised once each time an object is dragged into the bounds of an element that is acting as a drop target. This event is not raised if the element’s AllowDrop property is false.

Handling this event is optional for the drop target, and is not necessary for all drag-and-drop scenarios. You typically handle this event to provide a preview of the effects of the drag-and-drop operation, if appropriate for your application. Do not set the DragEventArgs.Effects property in the DragEnter event, as it will be overwritten in the DragOver event.

Identifier field

DragEnterEvent

Routing strategy

Bubbling

Delegate

DragEventHandler

The corresponding tunneling event is PreviewDragEnter.

The following example shows the DragEnter event handler for an Ellipse element. This code previews the effects of the drag-and-drop operation by saving the current Fill brush. It then checks to see if the DataObject being dragged over the ellipse contains string data that can be converted to a Brush. If so, the Brush is applied to the ellipse. The change is reverted in the DragLeave event handler. If the data cannot be converted to a Brush, no action is performed.

Private _previousFill As Brush = Nothing
Private Sub Ellipse_DragEnter(ByVal sender As System.Object, ByVal e As System.Windows.DragEventArgs)
    Dim ellipse = TryCast(sender, Ellipse)
    If ellipse IsNot Nothing Then
        ' Save the current Fill brush so that you can revert back to this value in DragLeave.
        _previousFill = ellipse.Fill

        ' If the DataObject contains string data, extract it.
        If e.Data.GetDataPresent(DataFormats.StringFormat) Then
            Dim dataString = e.Data.GetData(DataFormats.StringFormat)

            ' If the string can be converted into a Brush, convert it.
            Dim converter As New BrushConverter()
            If converter.IsValid(dataString) Then
                Dim newFill As Brush = CType(converter.ConvertFromString(dataString), Brush)
                ellipse.Fill = newFill
            End If
        End If
    End If
End Sub
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