#234 – Getting a DrawingVisual Object Rendered in a Window

A class deriving from DrawingVisual that draws one or more 2D objects needs to be hosted in another object in order to render the DrawingVisual object in a window or a page.

You can host the lower level control in either an UIElement or a FrameworkElementUIElement has basic support for layout and is the minimum functionality required in order to host a control within a Window (or a container control).

Here’s an example of overriding FrameworkElement to host our new control.

    public class EllAndRectHost : FrameworkElement
    {
        private EllipseAndRectangle _ellAndRect = new EllipseAndRectangle();

        // EllipseAndRectangle instance is our only visual child
        protected override Visual GetVisualChild(int index)
        {
            return _ellAndRect;
        }

        protected override int VisualChildrenCount
        {
            get
            {
                return 1;
            }
        }
    }

We create a FrameworkElement with one visual child, overriding GetVisualChild and VisualChildrenCount.

Now we can use this new element directly in XAML:

		<local:EllAndRectHost Margin="30"/>

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About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

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