Question

I want to add a few basic properties to an image. I would normally do this by doing

public class ExtendedImage: Image
{
}

But ofcourse this isn’t allowed because it’s sealed.

What other ways can I do this? The reason I want to extend Image, is because I’m looking to dynamically create and destroy objects, which get dragged and dropped around the application. So I want to add manipulation handlers, and gestures, as well as adding and removing the object from various display objects.

I don’t believe I’m able to inject an instance of Image into my base class, because then the data and the image will be decoupled when I try to have my dynamically created images respond to various manipulation events etc. (Based on the location the image is placed on in the main canvas, I need it to have different functionality.

Any advice on this issue is greatly appreciated.

Answer 1

You could use the Tag property to associate instances and get the kind of behavior you desire. Something like:

public class ExtendedImageController
{
    // add methods and properties as necessary
}

// client code
var img = new Image(); // ...
img.Tag = new ExtendedImageController(img); // with reference to image

// in some event handler:
var ctrl = (ExtendedImageController)img.Tag;
ctrl.DoCleanupThings(); 
// ...