First, please forgive (and correct!) any misconceptions – I’m brand new to anything .NET.
Me and my team are building an application in Silverlight, using the MVVM pattern. Right now, we a viewmodel for an object with various properties (e.g. its background color). The VM implements INotifyPropertyChanged so that when those properties are updated, listeners are notified.
The problem is that these are drag-and-drop objects on a canvas, and we want to run some logic every time the position on the canvas is changed. However, my understanding is that because Canvas.Left and Canvas.Top are attached properties I can’t treat them the same way as I did the properties native to the object.
Is there any way to make these attached properties work with INotifyPropertyChanged? If not, what’s the best way to react to changes in the Canvas.Left and Canvas.Top properties.
Thank you very much!
Two things:
(1) To keep with the MVVM pattern, I would suggest using style triggers for these attached properties and leave them out of your View Model altogether.
(2) Along those same lines, I wouldn’t have your view models know about concepts like “background color” that are purely view concerns. If there is something in your business logic/VM that keys a view concern like color, you can use value converters to translate from what the view model knows about to what the view needs to do.