我可以生成动态异步方法使用System.Linq.Ex pressions？ [英] Can I generate an async method dynamically using System.Linq.Expressions?

问题描述

我知道编译器不能异步拉姆达前pression转换为前pression树，但它是可以手动生成前pression树？

I know the compiler can't convert an async lambda expression to an expression tree, but is it possible to generate the expression tree manually ?

var expr = Expression.Lambda<Func<Task>>(
     // how do I use 'await' in the body here?
);
var func = expr.Compile();

我找不到异步与的任何方法或等待在防爆pression 类，但也许有另一种方式？

I can't find any method related to async or await in the Expression class, but perhaps there's another way?

推荐答案

的await 涉及的显著编译器重新编写;生成的IL是相当不同的原来的C＃，具有可变悬挂（上一个类）和分支，任务，延续等，这肯定是不是可以重新在的简单拉姆达，尽管最近有更丰富的防爆pression 支持（防爆pression.Block 等）的技术上的我想这大概是可以模仿大多数编译器的事情等待 - 但你可能去挺糊涂试图手工做。

await involves significant compiler re-writing; the generated IL is quite dissimilar to the original C#, with variable hoisting (onto a class) and branching, tasks, continuations, etc. It certainly isn't something that can be represented in a simple lambda, although in recent versions of .NET with richer Expression support (Expression.Block etc), technically I suppose it is probably possible to mimic most of the things the compiler does for await - but you'd probably go quite loopy trying to do it by hand.

没有，据我所知，没有任何设施的自动化的这个翻译存在防爆pression API中，坦白说我不会永远应该会存在。

No, AFAIK, no facility to automate this translation exists in the Expression API, and frankly I wouldn't ever expect there to be.

同样的大概可能是的ILGenerator 的说;坦率地说，据我所知唯一的轻松的方式（我用的是易非常不正确地）使用等待中的元编程将生成C＃和运行它通过罗斯林或 CSHARP codeProvider 。

The same probably could be say of ILGenerator; frankly, AFAIK the only "easy" way (and I use the word "easy" quite incorrectly) to use await in meta-programming would be to generate C# and run it through roslyn or CSharpCodeProvider.

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