Question

I have an application with two Canvas controls. When the application starts, it loads from a DLL a UserControl which is basically Canvas with a bunch of XAML code.

I want to be able to display this control in the two Canvases, however, when I use the ContentPresenter and bind it in both Canvases to the control loaded from the DLL it shows only on one canvas and on the other it doesn’t. I guess it’s something that has to do with the fact that I’m actually using the same resource in two different Canvases, but since I wanted to avoid using too much memory (the control loaded from the DLL is pretty heavy) I didn’t want to create two copies of the same control.

Does anyone have a better approach / solution for this situation?

This is the XAML for showing the loaded control in one of the two canvases (the other canvas uses similar code)

<Canvas Width="{Binding MapModel.MapControl.Bounds.Width}" Height="{Binding MapModel.MapControl.Bounds.Height}">
    <Canvas.Background>
         <VisualBrush>
             <VisualBrush.Visual>
                  <ContentPresenter Content="{Binding MapModel.MapControl}" />
             </VisualBrush.Visual>
         </VisualBrush>
    </Canvas.Background>
 </Canvas>

And loading from the DLL is performed by:

  // Load the map library assembly (Using reflection)
  Assembly asm = Assembly.LoadFile(m_fileName);
  Type[] tlist = asm.GetTypes();

  // Find the class that represents the airport XAML drawing in the assembly, if it finds the airport class then 
  // set the value to be an instance of that class.
  foreach (Type t in tlist)
  {
    if (t.Name == "Map")
    {
      MapControl = Activator.CreateInstance(t) as UserControl;
      break;
    }
  }

Thanks in advance!

Answer 1

Set attribute x:Shared="False" to your resource.
It is 'true' so wpf creates one resource (for optimize performance) by default. When you set it 'false' wpf creates new instance per request.
There are sample of this