How to use disposable view models in WPF?

问题

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.

回答1:

I accomplished this by doing the following:

Removing the StartupUri property from App.xaml.

Defining my App class as follows:

public partial class App : Application
{
    public App()
    {
        IDisposable disposableViewModel = null;

        //Create and show window while storing datacontext
        this.Startup += (sender, args) =>
        {
            MainWindow = new MainWindow();
            disposableViewModel = MainWindow.DataContext as IDisposable;

            MainWindow.Show();
        };

        //Dispose on unhandled exception
        this.DispatcherUnhandledException += (sender, args) => 
        { 
            if (disposableViewModel != null) disposableViewModel.Dispose(); 
        };

        //Dispose on exit
        this.Exit += (sender, args) =>
        { 
            if (disposableViewModel != null) disposableViewModel.Dispose(); 
        };
    }
}

回答2:

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();
    }

来源：https://stackoverflow.com/questions/6983801/how-to-use-disposable-view-models-in-wpf

标签

wpf

mvvm

idisposable