How to extend Windows.UI.Xaml.Shapes.Shape in Win Store App (8.1)?

Question

After several hours of research on how to extend the Windows.UI.Xaml.Shapes.Shape class, I need to ask you guys if anybody can help me.

Basically I need an ordinary rectangle (since its sealed, I cannot extend the Windows.UI.Xaml.Shapes.Rectangle class) and add some members to it. So I need a class which draws a ordinary rectangle with additional members.

Answer 1

Have you tried Extension Methods ?

public static class MyExtensions
{
    public static Size GetSize(this Windows.UI.Xaml.Shapes.Rectangle rectangle)
    {
        return rectangle.RenderSize;
    }
}

public sealed partial class MainPage : Page
{
    public MainPage()
    {
        this.InitializeComponent();

        Rectangle rectangle = new Rectangle();
        Debug.WriteLine(rectangle.GetSize());
    }
}

The Windows Runtime C# projection has a bunch of extensions, eg, AsInputStream .

For a great example of using extensions with Windows Runtime APIs see this article in the MSDN Magazine .

Answer 2

The actual answer to the question would be to really extend a class by the Shape class ( Windows.UI.Xaml.Shapes.Shape ).

Nevertheless I found two solutions for my problem where it isnt necessary to use the Shape class:

1. extend your class by the Path class
   • since Path isnt sealed this is possible (see how to draw a custom graphic with this example http://code.msdn.microsoft.com/windowsapps/Drawing-bfc39296/ )
2. create your custom control based on an ordinary class
   • see this example here how to do this: http://code.msdn.microsoft.com/windowsapps/XAML-user-and-custom-a8a9505e