0

我有一些类似于以下内容:

public class MyClass
{
    private List<MyOjectMapping> mappings;

    public void Start()
    {
        foreach (var mapping in mappings)
        {
            mapping.ObjectA.PropertyA.PropertyChanged += (s, e) =>
            {
                // do something with mapping.ObjectB
            };
        }
    }

    public void Stop()
    {
        // unhook events
    }
}

public class MyObject : INotifyPropertyChanged
{
    public object PropertyA;
    public object PropertyB;
}

public class MyOjectMapping
{
    public object SomeSortOfKey;
    public MyObject ObjectA;
    public MyObject ObjectB;
}

如您所见,我正在尝试对 lambda 事件处理程序中的 foreach 迭代器执行一些操作。这行得通,但是这样做,我不知道如何在 Stop() 方法中解开事件。

我应该如何连接 PropertyChanged 事件,以便以后可以将其解开并仍然可以访问 foreach 迭代器?

谢谢

4

1 回答 1

3

如果您想使用多个匿名事件处理程序并且以后仍然能够分离它们,您可以简单地将分离操作存储在单独的列表中,类似于:

// these actions should be invoked during cleanup
private readonly List<Action> _cleanupActions = new List<Action>();

public void Start()
{
    foreach (var m in mappings)
    {
        // you need both closures in order to reference them inside
        // the cleanup action
        var mapping = m;
        PropertyChangedEventHandler handler = (s, e) => { /* ... */ };

        // attach now
        mapping.PropertyChanged += handler;

        // add a cleanup action to detach later
        _cleanupActions.Add(() => mapping.PropertyChanged -= handler);

}

public void Stop()
{
    // invoke all cleanup actions
    foreach (var action in _cleanupActions)
        action();
}

这很简洁,因为它允许任意复杂的清理操作,并且它捕获正确的对象对及其事件处理程序。

于 2014-05-09T10:12:34.187 回答