c# - Observable.FromEvent 可以与 DataContextChanged 一起使用吗

Question

我想获取控件的 DataContext 作为 IObservable。我试过这个:

Observable.FromEvent<DependencyPropertyChangedEventHandler,
     DependencyPropertyChangedEventArgs>
     (a => this.DataContextChanged += a, a => this.DataContextChanged -= a)
     .Subscribe(e => MessageBox.Show(e.NewValue.ToString()));

编译正常，但在调用 Subscribe 时抛出异常:错误绑定(bind)到目标方法。

我猜这是因为 DependencyPropertyChangedEventArgs 没有继承自事件参数，但我不确定。任何有关正确执行此操作的建议都将不胜感激。

Answer 1

FromEvent 的其他重载之一允许您从方法中自己创建委托(delegate)。允许您这样做:

Observable.FromEvent
    <DependencyPropertyChangedEventHandler, DependencyPropertyChangedEventArgs>
    (a => new DependencyPropertyChangedEventHandler(
        new Action<object, DependencyPropertyChangedEventArgs>((s, e) => a(e))),
        h => this.DataContextChanged += h, h => this.DataContextChanged -= h)
        .Subscribe(e => MessageBox.Show(e.NewValue.ToString()));

这似乎有效