重大变更破坏了 Rx 样本

发布于 2024-12-25 10:41:37 字数 729 浏览 0 评论 0 原文

Rx Wiki 的 101 个 Rx 示例中的一些示例实际上不再起作用。我认为这是因为我拥有最新的 Rx 版本（1.0.10621.2），但我想确认并看看如何让它们工作。

例如，以下示例代码不起作用：

class ObserveEvent_Generic
{
    public class SomeEventArgs : EventArgs { }
    public static event EventHandler<SomeEventArgs> GenericEvent;

    static void Main()
    {
        // To consume GenericEvent as an IObservable:
        IObservable<IEvent<SomeEventArgs>> eventAsObservable = Observable.FromEvent<SomeEventArgs>(
            ev => GenericEvent += ev,
            ev => GenericEvent -= ev);
    }
}

缺少 IEvent 并且“ev => GenericEvent += ev”导致“无法将类型 System.Action 隐式转换为 <代码>System.EventHandler 错误。

原文

There are a few samples from the 101 Rx Samples from Rx Wiki that don't actually work anymore. I think it's because the latest Rx version I have (1.0.10621.2) but I'd like to confirm and see how I can get them to work.

For example, the following sample code doesn't work:

class ObserveEvent_Generic
{
    public class SomeEventArgs : EventArgs { }
    public static event EventHandler<SomeEventArgs> GenericEvent;

    static void Main()
    {
        // To consume GenericEvent as an IObservable:
        IObservable<IEvent<SomeEventArgs>> eventAsObservable = Observable.FromEvent<SomeEventArgs>(
            ev => GenericEvent += ev,
            ev => GenericEvent -= ev);
    }
}

The IEvent is missing and "ev => GenericEvent += ev" is causing a "Cannot implicitly convert type System.Action<xxx> to System.EventHandler<xxx> error.

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苏佲洛 2025-01-01 10:41:37

在这种情况下，您有几种选择。第一个是提供与标准 EventHandler 模式匹配的委托（生成的 Observable 的类型为 IObservable）。请注意，我提供的 lamda 接受“o”（“发送者”），但未使用此参数：

IObservable<SomeEventArgs> eventAsObservable = 
Observable.FromEvent<SomeEventArgs>
(
    ev => GenericEvent += (o,e) => ev(e),
    ev => GenericEvent -= (o,e) => ev(e)
);

特别是在您的情况下（静态事件...哎呀！），我将不愿信任取消订阅会真正正确地清理，并且根据使用情况，您可能最终会出现严重的内存泄漏。作为替代方案，您可以指定委托类型。注意这里 FromEvent 的额外泛型参数

IObservable<SomeEventArgs> eventAsObservable = 
Observable.FromEvent<EventHandler<SomeEventArgs>, SomeEventArgs>
(
    ev => GenericEvent += ev,
    ev => GenericEvent -= ev
);

另一种替代方案是将源/发送者对象的处理移至观察者（使可观察类型为 IObservable>) 是使用 FromEventPattern 方法。我在某些构建中使用此方法遇到了一些麻烦，因此您的情况可能会有所不同，但这是替代方案：

IObservable<EventPattern<SomeEventArgs>> eventAsObservable = 
Observable.FromEventPattern<SomeEventArgs>
(
    ev => GenericEvent += ev,
    ev => GenericEvent -= ev
);

希望这会有所帮助。

You have a few options in this case. The first is to provide a delegate that matches the standard EventHandler pattern (the resulting Observable is of type IObservable<SomeEventArgs>). Notice the lamda I provided accepts "o" (the "sender"), but this param is not used:

IObservable<SomeEventArgs> eventAsObservable = 
Observable.FromEvent<SomeEventArgs>
(
    ev => GenericEvent += (o,e) => ev(e),
    ev => GenericEvent -= (o,e) => ev(e)
);

Especially in your situation (static event... yikes!), I would be reticent to trust that the unsubscribe would truly cleanup properly and you might end up with a nasty memory leak depending on usage. As an alternative, you can specify the delegate type. Notice here the extra generic parameter to FromEvent

IObservable<SomeEventArgs> eventAsObservable = 
Observable.FromEvent<EventHandler<SomeEventArgs>, SomeEventArgs>
(
    ev => GenericEvent += ev,
    ev => GenericEvent -= ev
);

One more alternative that moves the handling of the source/sender object to the Observer (making the observable of type IObservable<EventPattern<SomeEventArgs>>) is to use the FromEventPattern method. I've had a little trouble with this method in some builds, so your mileage may vary, but here is that alternative:

IObservable<EventPattern<SomeEventArgs>> eventAsObservable = 
Observable.FromEventPattern<SomeEventArgs>
(
    ev => GenericEvent += ev,
    ev => GenericEvent -= ev
);

Hopefully this helps a bit.

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