When Drag-n-Drop file (FileDrop), the indicator doesn't change [VS 2013 Preview]

I do drag-and-drop operation for Excel files, so I wrote the following handler for DragEnter (Window):

    Private Sub OnExcelFileDragEnter(sender As Object, e As DragEventArgs) Handles Me.DragEnter
        e.Effects = DragDropEffects.Copy
        If e.Data.GetDataPresent(DataFormats.FileDrop) Then
            Dim fileName = DirectCast(e.Data.GetData(DataFormats.FileDrop), String())(0)
            Dim ext = System.IO.Path.GetExtension(fileName)
            If {".XLSX", ".XLSM"}.Contains(ext.ToUpper()) Then
                e.Effects = DragDropEffects.Copy
            Else
                e.Effects = DragDropEffects.None
            End If
        Else
            e.Effects = DragDropEffects.None
        End If
    End Sub

Private Sub OnGiveFeedbackExcel(sender As Object, e As GiveFeedbackEventArgs) Handles Me.GiveFeedback
     If e.Effects = DragDropEffects.None Then Mouse.SetCursor(Cursors.No)
End Sub

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