我怎样才能实现与DynamicObject事件acessors在C＃ [英] How can I implement event acessors with DynamicObject in C#

问题描述

我想实现一个通用的包装级使用C＃的DynamicObject Qt的等级制度。不过，我想写以下code：

I am trying to implement a generic Wrapper-Class for Qt's class system using C#'s DynamicObject. However, I want to write the following code:

dynamic obj = new SomeWrapperClass(....); // This extends DynamicObject
obj.OnMyEvent += (Action)(() => Console.WriteLine("DO something!"));

以上是有效的code根据VS2010（显式强制转换为行动是必需的），但究竟如何做我抓使用DynamicObject的方法，这种说法？

The above is valid code according to VS2010 (the explicit cast to Action is required), but how exactly do i "catch" that statement using DynamicObject's methods?

我想实现TryGetMember（），它被调用的语句，但我不知道我要回到使其工作。

I tried implementing TryGetMember() and it gets called for the statement, but I have no idea what I have to return to make it work.

任何提示？

推荐答案

反射是你的朋友在这一个。关于你的第二线所产生的code看起来是这样的（大约）：

Reflector is your friend on this one. The code generated for your second line looks something like this (approximately):

if(Binder.IsEvent("OnMyEvent", typeof(SomeWrapperClass)))
{
    Binder.InvokeMember("add_OnMyEvent", obj, myAction);
}
else
{
    var e = Binder.GetMember("OnMyEvent", obj);
    var ae = Binder.BinaryOperation(ExpressionType.AddAssign, e, myAction);
    Binder.SetMember("OnMyEvent", obj, ae);
}

如果您不能使用 OnMyEvent 真实的事件（在这种情况下，你可以在默认瘦 DynamicObject 实现），那么你就需要返回的东西，它实现中用addAssign 返回像多播委托。我建议前，如果可能的话...

If you can't use a real event for OnMyEvent (in which case you can lean on the default DynamicObject implementation), then you'll need to return something that implements AddAssign returning something like a multicast delegate. I'd suggest the former, if possible...

有关的乐趣，这里有一个hackish的例子，动态结合OnMyEvent到OnMyOtherEvent：

For fun, here's a hackish example that dynamically binds OnMyEvent to OnMyOtherEvent:

public class SomeWrapperClass : DynamicObject
{
    public event Action OnMyOtherEvent;

    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        if (binder.Name == "OnMyEvent")
        {
            result = OnMyOtherEvent;
            return true;
        }
        return base.TryGetMember(binder, out result);
    }

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        if (binder.Name == "OnMyEvent" && value is Action)
        {
            OnMyOtherEvent = (Action)value;
            return true;
        }
        return TrySetMember(binder, value);
    }

    public void Test()
    {
        if (OnMyOtherEvent != null)
            OnMyOtherEvent();
    }

    private static void TestEventHandling()
    {
        dynamic obj = new SomeWrapperClass(); // This extends DynamicObject
        obj.OnMyEvent += (Action)(() => Console.WriteLine("DO something!"));
        obj.Test();
    }
}

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