检查Action是否为异步Lambda [英] Check if Action is async lambda

问题描述

因为我可以将动作定义为

Since I can define an Action as

Action a = async () => { };

我能以某种方式确定(在运行时)动作a是否异步?

Can I somehow determine (at run time) whether the action a is async or not?

推荐答案

否-至少不明智. async只是源代码注释，用于告诉C#编译器您确实需要异步函数/匿名函数.

No - at least not sensibly. async is just a source code annotation to tell the C# compiler that you really want an asynchronous function/anonymous function.

您可以获取委托的MethodInfo并检查其是否具有适当的属性.我个人不会-需要知道的是设计气味.特别是，请考虑一下，如果您将大部分代码从lambda表达式中重构为另一个方法，然后使用:

You could fetch the MethodInfo for the delegate and check whether it has an appropriate attribute applied to it. I personally wouldn't though - the need to know is a design smell. In particular, consider what would happen if you refactored most of the code out of the lambda expression into another method, then used:

Action a = () => CallMethodAsync();

到那时，您没有拥有异步lambda，但是语义是相同的.为什么要让使用委托的任何代码表现不同?

At that point you don't have an async lambda, but the semantics would be the same. Why would you want any code using the delegate to behave differently?

此代码似乎有效，但我强烈建议不要使用它:

This code appears to work, but I would strongly recommend against it:

using System;
using System.Runtime.CompilerServices;

class Test
{
    static void Main()        
    {
        Console.WriteLine(IsThisAsync(() => {}));       // False
        Console.WriteLine(IsThisAsync(async () => {})); // True
    }

    static bool IsThisAsync(Action action)
    {
        return action.Method.IsDefined(typeof(AsyncStateMachineAttribute),
                                       false);
    }
}

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