处置WPF用户控件

Question

我创建了一个自定义WPF用户控件,供第三方使用.我的控件有一个一次性的私有成员,我想确保一旦包含窗口/应用程序关闭,它的dispose方法将始终被调用.但是,UserControl不是一次性的.我尝试实现IDisposable接口并订阅Unloaded事件,但在主机应用程序关闭时都不会被调用.如果可能的话,我不想依赖我控制的消费者记住调用特定的Dispose方法.

 public partial class MyWpfControl : UserControl
 {
     SomeDisposableObject x;

     // where does this code go?
     void Somewhere() 
     {
         if (x != null)
         {
             x.Dispose();
             x = null;
         }

     }
 }

到目前为止,我找到的唯一解决方案是订阅Dispatcher的ShutdownStarted事件.这是一种合理的方法吗？

this.Dispatcher.ShutdownStarted += Dispatcher_ShutdownStarted;

Answer 1

有趣的博客文章:

http://geekswithblogs.net/cskardon/archive/2008/06/23/dispose-of-a-wpf-usercontrol-ish.aspx

它提到订阅Dispatcher_ShutDownStarted来处理你的资源.

Answer 2

Dispatcher.ShutdownStarted事件仅在应用程序结束时触发.当控件不再使用时,调用处理逻辑是值得的.特别是在应用程序运行时期间多次使用控件时,它会释放资源.所以ioWint的解决方案更可取.这是代码:

public MyWpfControl()
{
     InitializeComponent();
     Loaded += (s, e) => { // only at this point the control is ready
         Window.GetWindow(this) // get the parent window
               .Closing += (s1, e1) => Somewhere(); //disposing logic here
     };
}

Answer 3

你必须小心使用析构函数.这将在GC Finalizer线程上调用.在某些情况下,您的释放可能不喜欢在与创建它们的线程不同的线程上释放的资源.

Answer 4

我使用以下Interactivity Behavior为WPF UserControls提供卸载事件.您可以在UserControls XAML中包含该行为.因此,您可以拥有该功能,而无需将逻辑放在每个UserControl中.

XAML声明:

xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"

<i:Interaction.Behaviors>
    <behaviors:UserControlSupportsUnloadingEventBehavior UserControlClosing="UserControlClosingHandler" />
</i:Interaction.Behaviors>

CodeBehind处理程序:

private void UserControlClosingHandler(object sender, EventArgs e)
{
    // to unloading stuff here
}

行为代码:

/// <summary>
/// This behavior raises an event when the containing window of a <see cref="UserControl"/> is closing.
/// </summary>
public class UserControlSupportsUnloadingEventBehavior : System.Windows.Interactivity.Behavior<UserControl>
{
    protected override void OnAttached()
    {
        AssociatedObject.Loaded += UserControlLoadedHandler;
    }

    protected override void OnDetaching()
    {
        AssociatedObject.Loaded -= UserControlLoadedHandler;
        var window = Window.GetWindow(AssociatedObject);
        if (window != null)
            window.Closing -= WindowClosingHandler;
    }

    /// <summary>
    /// Registers to the containing windows Closing event when the UserControl is loaded.
    /// </summary>
    private void UserControlLoadedHandler(object sender, RoutedEventArgs e)
    {
        var window = Window.GetWindow(AssociatedObject);
        if (window == null)
            throw new Exception(
                "The UserControl {0} is not contained within a Window. The UserControlSupportsUnloadingEventBehavior cannot be used."
                    .FormatWith(AssociatedObject.GetType().Name));

        window.Closing += WindowClosingHandler;
    }

    /// <summary>
    /// The containing window is closing, raise the UserControlClosing event.
    /// </summary>
    private void WindowClosingHandler(object sender, CancelEventArgs e)
    {
        OnUserControlClosing();
    }

    /// <summary>
    /// This event will be raised when the containing window of the associated <see cref="UserControl"/> is closing.
    /// </summary>
    public event EventHandler UserControlClosing;

    protected virtual void OnUserControlClosing()
    {
        var handler = UserControlClosing;
        if (handler != null) 
            handler(this, EventArgs.Empty);
    }
}

Answer 5

我的情况略有不同,但我想知道当托管我的用户控件的父窗口关闭/关闭时,意图是相同的.视图(即我的usercontrol)应该调用oncloseView上的演示者来执行某些功能并执行清理.(我们正在WPF PRISM应用程序上实现MVP模式).

我只是想在usercontrol的Loaded事件中,我可以将ParentWindowClosing方法连接到Parent windows Closing事件.这样我的Usercontrol可以在父窗口关闭时知道并采取相应的行动!