Question

I am trying to implemented a custom dragging operation to sort panels.

I assign an object to a variable in the MouseDown event and track it’s relative position by examining the MouseMove event of the neighbouring panels as I drag the mouse over them.

Private Sub ThumbnailMouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs)

    _thumbnailMove = DirectCast(sender, Windows.Forms.Control)  ‘The object to move

End Sub

The problem is that the Sender parameter of the MouseMove event never changes – it always returns the object that received the MouseDown event.

Private Sub ThumbnailMouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs)

    Console.WriteLine(sender.Name)  'Always returns the name of the _thumbnailToMove

End Sub

Why is the Sender argument of MouseMove not returning the actual object that the mouse is currently over?

Answer 1

To override this behaviour, set the Control.Capure property to False.

Private Sub ThumbnailMouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs)

    DirectCast(sender, Windows.Forms.Control).Capture = False   'Don't capture the mouse
    _thumbnailMove = DirectCast(sender, Windows.Forms.Control)

End Sub

And now the MouseMove event returns the actual object that the mouse moves over!