Imports System.Windows.Controls.Primitives
 
Public Class CustomControl1
    Inherits System.Windows.Controls.Control
 
    Dim sw As New Stopwatch
    Dim AnzahlRechtecke As Integer
 
    Shared Sub New()
        DefaultStyleKeyProperty.OverrideMetadata(GetType(CustomControl1), New _
          FrameworkPropertyMetadata(GetType(CustomControl1)))
    End Sub
 
 
    Protected Overrides Sub OnRender(drawingContext As DrawingContext)
        MyBase.OnRender(drawingContext)
 
        Dim myBrush As New SolidColorBrush(Colors.LimeGreen)
        Dim myPen As New Pen(myBrush, 1)
        Dim x, y As Integer
 
        sw.Reset()
        sw.Start()
        AnzahlRechtecke = 0
 
        For x = 0 To 120 - 1
            For y = 0 To 90 - 1
                drawingContext.DrawRectangle(myBrush, myPen, New Rect(8 * x, 8 _
                  * y, 5, 5))
                AnzahlRechtecke += 1
            Next
        Next
 
        sw.Stop()
 
        Debug.WriteLine(Now & vbTab & AnzahlRechtecke & " Rechtecke gezeichnte" & _
          "in " & sw.ElapsedMilliseconds & " ms")
 
    End Sub
End Class

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="800" Width="1024" _
      xmlns:my="clr-namespace:TestWpfPerformance">
    <Grid Name="Grid1">
        <my:CustomControl1 HorizontalAlignment="Left"  x:Name="CustomControl11" _
          VerticalAlignment="Top" />
        <Button Content="Button" Height="23" HorizontalAlignment="Left" _
        Margin="869,21,0,0" Name="Button1" VerticalAlignment="Top" Width="75" _
        Click="Button1_Click" />
    </Grid>
</Window>

Class MainWindow 
 
 
    Private Sub Button1_Click(sender As System.Object, e As _
      System.Windows.RoutedEventArgs) Handles Button1.Click
        CustomControl11.InvalidateVisual()
    End Sub
End Class