Question

How do I ensure view models are properly disposed of if they reference unmanaged resources or have event handlers such as handling elapsed on a dispatcher timer. In the first case, a finaliser is an option, although not ideal, but in the latter, it will never be called. How can we tell when there is no longer a view attached to the view model.

Answer 1

One possible, although not perfect solution:

Implement IDisposable on the View Model, then use this extension method in the constructor of the view.

    public static void HandleDisposableViewModel(this FrameworkElement Element)
    {
        Action Dispose = () =>
            {
                var DataContext = Element.DataContext as IDisposable;
                if (DataContext != null)
                {
                    DataContext.Dispose();
                }
            };
        Element.Unloaded += (s, ea) => Dispose();
        Element.Dispatcher.ShutdownStarted += (s, ea) => Dispose();
    }