DrawingVisual.RenderOpen Method ()


Opens the DrawingVisual object for rendering. The returned DrawingContext value can be used to render into the DrawingVisual.

Namespace:   System.Windows.Media
Assembly:  PresentationCore (in PresentationCore.dll)

public DrawingContext RenderOpen()

Return Value

Type: System.Windows.Media.DrawingContext

A value of type DrawingContext.

When you call the Close method of the DrawingContext, the current drawing content replaces any previous drawing content defined for the DrawingVisual. This means that there is no way to append new drawing content to existing drawing content.

In the following example, a DrawingVisual object is created, and its DrawingContext returned.

// Create a DrawingVisual that contains a rectangle.
private DrawingVisual CreateDrawingVisualRectangle()
    DrawingVisual drawingVisual = new DrawingVisual();

    // Retrieve the DrawingContext in order to create new drawing content.
    DrawingContext drawingContext = drawingVisual.RenderOpen();

    // Create a rectangle and draw it in the DrawingContext.
    Rect rect = new Rect(new System.Windows.Point(160, 100), new System.Windows.Size(320, 80));
    drawingContext.DrawRectangle(System.Windows.Media.Brushes.LightBlue, (System.Windows.Media.Pen)null, rect);

    // Persist the drawing content.

    return drawingVisual;

The order in which you draw into the drawing context is important—each succeeding drawing is drawn on top of the others. In the following example, the rectangle is drawn first, then the text.

// Retrieve the DrawingContext in order to draw into the visual object.
DrawingContext drawingContext = drawingVisual.RenderOpen();

// Draw a rectangle into the DrawingContext.
Rect rect = new Rect(new Point(160, 100), new Size(320, 80));
drawingContext.DrawRectangle(Brushes.LightBlue, (Pen)null, rect);

// Draw a formatted text string into the DrawingContext.
   new FormattedText("Hello, world",
      new Typeface("Verdana"),
      36, Brushes.Black),
      new Point(200, 116));

// Persist the drawing content.

.NET Framework
Available since 3.0
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