Private offset As Point = Point.Empty
 
Protected Overrides Sub OnMouseDown(e As MouseEventArgs)
	MyBase.OnMouseDown(e)
	If (e.Button And MouseButtons.Left) = MouseButtons.Left Then
		offset = e.Location
		DoDragDrop(e, DragDropEffects.Move)
	End If
End Sub
'AllowDrop muss true sein!
Protected Overrides Sub OnDragDrop(e As DragEventArgs)
	MyBase.OnDragDrop(e)
	SetLocation(e)
End Sub
 
Protected Overrides Sub OnDragOver(e As DragEventArgs)
	MyBase.OnDragOver(e)
	e.Effect = DragDropEffects.Move
	SetLocation(e)
End Sub
 
Private Sub SetLocation(e As DragEventArgs)
	Dim clientPoint As Point = Parent.PointToClient(New Point(e.X, e.Y))
	If e.Effect = DragDropEffects.Move Then
		Me.Location = Point.Subtract(clientPoint, New Size(offset))
	End If
End Sub

Gruß
Christoph