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PODrawingVisual is not refreshed
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copied!<p>I create my own <code>FrameworkElement</code> and override <code>VisualChildrenCount{get;}</code> and <code>GetVisualChild(int index)</code> by returning my own <code>DrawingVisual</code> instance. </p> <p>If I modify the content of the visual after initial rendering (e.g. in timer handler) using <code>DrawingVisual.RenderOpen()</code> and drawing into the context, the element is not refreshed.</p> <p>Here's the simplest sample:</p> <pre><code>using System; using System.Windows; using System.Windows.Media; using System.Windows.Threading; namespace VisualTest { public class TestControl : FrameworkElement { private readonly DrawingVisual _visual = new DrawingVisual(); public TestControl() { Draw(false); var timer = new DispatcherTimer {Interval = new TimeSpan(0, 0, 2)}; timer.Tick += (sender, args) => { Draw(true); InvalidateVisual(); timer.Stop(); }; timer.Start(); } protected override Visual GetVisualChild(int index) { return _visual; } protected override int VisualChildrenCount { get { return 1; } } private void Draw(bool second) { DrawingContext ctx = _visual.RenderOpen(); if (!second) ctx.DrawRoundedRectangle(Brushes.Green, null, new Rect(0, 0, 200, 200), 20, 20); else ctx.DrawEllipse(Brushes.Red, null, new Point(100, 100), 100, 100); ctx.Close(); } } } </code></pre> <p><code>InvalidateVisual()</code> does nothing. Although if you resize the window containing the element, it gets updated.</p> <p>Any ideas on how to properly refresh the content? Preferably <strong>without</strong> introducing new dependency properties for my element.</p>

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