this is very simple example to show my question.
1
public class TestControl : UserControl
{
public TestControl()
{
}
protected override void OnRender(DrawingContext context)
{
drawCircle(context);
base.OnRender(context);
}
private void drawCircle(DrawingContext context)
{
context.DrawEllipse(Brushes.Red, null, new Point(50, 50), 50, 50);
}
public void drawRect()
{
DrawingContext context = new DrawingVisual().RenderOpen();
context.DrawRectangle(Brushes.Green, null, new Rect(0, 0,200, 100));
}
}
2、 The Window front
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="300"/>
<RowDefinition Height="50"/>
</Grid.RowDefinitions>
<Grid Background="White" x:Name="root">
<local:TestControl x:Name="progressBar" HorizontalContentAlignment="Stretch"/>
</Grid>
<Grid Grid.Row="1">
<Button Content="Init" Click="Button_Click" Width="100" Height="40"/>
</Grid>
</Grid>
and 3、
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
Loaded += MainWindow_Loaded;
}
private void MainWindow_Loaded(object sender, RoutedEventArgs e)
{
}
private void Button_Click(object sender, RoutedEventArgs e)
{
progressBar.drawRect();
}
}
Question is:Red Circle in Render() showwed in windows.the green Rect never to show。 dont know why
I think when render finished,the DrawingContext disposed,how to append in the first drawingcontext
