wpf forcing update UI window during a procedure

Question

Hi everyone!

I need only to show a custom control (a clock with rotating hands) and with this to replace the mouse cursor, if I use a file .cur or .ani to replace the mouse cursor Me.CUrsor = New Cursor("absolute path of the .ani file") there is no problem: I can change the cursor during a procedure: but the quality of the animation is very bad, and, also for other reasons, I'd prefer to use my little user-control. The problem is that if I write:

Me.gridScreen.Visibility = Visibility.Visible

' some operations that takes about 1 second

Me.gridScreen.Visibility = Visibility.Hidden

(gridScreen is the grid that contains the user-control)

Obviously I can see nothing, because the update of the UI happens at the end of the procedure. I have tried Me.UpdateLayout(), but it doesn't work.

I have tryed to use the dispacker in many way but none that works :-(

This is my lost attempt:

(uCurClock is the usercontrol, gridScreen a Grid placed at the top-level in the window, with trasparent background, that contains the usercontrol)

Private Sub showClock()G
    Dim thread = New System.Threading.Thread(AddressOf showClockIntermediate)
    thread.Start()
End Sub

Private Sub hideClock()
    Dim thread = New System.Threading.Thread(AddressOf hideClockIntermediate)
    thread.Start()
End Sub

Private Sub showClockIntermediate()
    Me.Dispatcher.BeginInvoke(DispatcherPriority.Normal, New Action(AddressOf showClockFinale))
End Sub

Private Sub hideClockIntermediate()
    Me.Dispatcher.BeginInvoke(DispatcherPriority.Normal, New Action(AddressOf hideClockFinale))
End Sub

Private Sub showClockFinale()
    Dim pt As Point = Mouse.GetPosition(Nothing)
    Me.uCurClock.Margin = New Thickness(pt.X - 9, pt.Y - 9, 0, 0)
    Me.gridScreen.Visibility = Visibility.Visible
    Me.Cursor = Cursors.None
    Me.UpdateLayout()
End Sub

Private Sub hideClockFinale()
    Me.gridScreen.Visibility = Visibility.Hidden
    Me.Cursor = Cursors.Arrow
    Me.UpdateLayout()
End Sub

Private Sub u_MouseMove(ByVal sender As System.Object, ByVal e As MouseEventArgs) Handles gridScreen.MouseMove
    Dim pt As Point = e.GetPosition(Nothing)
    Me.uCurClock.Margin = New Thickness(pt.X - 9, pt.Y - 9, 0, 0)

    e.Handled = True
End Sub

Private Sub u_MouseEnter(ByVal sender As System.Object, ByVal e As MouseEventArgs) Handles gridScreen.MouseEnter
    Me.uCurClock.Visibility = Visibility.Visible

    e.Handled = True
End Sub

Private Sub u_MouseLeave(ByVal sender As System.Object, ByVal e As MouseEventArgs) Handles gridScreen.MouseLeave
    Me.uCurClock.Visibility = Visibility.Hidden

    e.Handled = True
End Sub

PIleggi