异步迭代任务＆LT;＆IEnumerable的LT; T＆GT;＆GT; [英] Asynchronous iterator Task<IEnumerable<T>>

问题描述

我想实现一个返回一个迭代异步函数。这个想法是：

I’m trying to implement an asynchronous function that returns an iterator. The idea is the following:

    private async Task<IEnumerable<char>> TestAsync(string testString)
    {
        foreach (char c in testString.ToCharArray())
        {
            // do other work
            yield return c;
        }
    }

但是，该功能不能是迭代器块，因为任务℃的错误信息; IEnumerable的＆LT;焦炭＆GT;＆GT; 不是一个迭代器接口类型。有没有解决的办法？

However, there is an error message that the function cannot be an iterator block because Task<IEnumerable<char>> is not an iterator interface type. Is there a solution?

推荐答案

这听起来像你可能真的要寻找的是类似的＆的IObservable LT; T＆GT; ，这有点像一个基于推送的异步的IEnumerable＆LT; T＆取代。请参见无扩展，微软开放技术又名接收（code Apache-下许可2.0）（没有隶属关系）为与的IObservable＆LT工作方法，一个巨大的主机; T＆GT;使它象LINQ到对象和更多的工作。

It sounds like what you may really be looking for is something like IObservable<T>, which is sort of like a push-based asynchronous IEnumerable<T>. See Reactive Extensions, a.k.a. Rx from Microsoft Open Technologies (code licensed under Apache-2.0) (no affiliation) for a huge host of methods that work with IObservable<T> to make it work like LINQ-to-Objects and more.

与IEnumerable的＆LT的问题; T＆GT;是没有什么，真正使枚举本身异步的。如果你不希望添加在RX的依赖（这是真的什么使的IObservable＆LT; T＆GT;光泽），这种替​​代可能会为你工作：

The problem with IEnumerable<T> is that there's nothing that really makes the enumeration itself asynchronous. If you don't want to add a dependency on Rx (which is really what makes IObservable<T> shine), this alternative might work for you:

public async Task<IEnumerable<char>> TestAsync(string testString)
{
    return GetChars(testString);
}

private static IEnumerable<char> GetChars(string testString)
{
    foreach (char c in testString.ToCharArray())
    {
        // do other work
        yield return c;
    }
}

但我想指出的是，不知道什么的实际被异步完成的，有可能是一个更好的方式来实现自己的目标。在code你贴实际上将做任何事情异步的，我真的不知道，如果在 //事情做其他工作的无是异步的（在这种情况下，这不是你的潜在问题的解决方案，虽然它会让你的code编译）。

though I'd like to point out that without knowing what's actually being done asynchronously, there may be a much better way to accomplish your goals. None of the code you posted will actually do anything asynchronously, and I don't really know if anything in // do other work is asynchronous (in which case, this isn't a solution to your underlying problem though it will make your code compile).

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