基于回调异步方法转换为awaitable任务的最佳方式 [英] Best way to convert callback-based async method to awaitable task

问题描述

什么是转换的最佳方式/包装经典异步使用回调的东西，返回（awaitable）任务的方法？

What would be the best way to convert/wrap a "classic" asynchronous method that uses a callback to something that returns a (awaitable) Task?

例如，考虑以下方法：

public void GetStringFromUrl(string url, Action<string> onCompleted);

我知道要包装成返回任务的方法这个问题的唯一办法是：

The only way I know of to wrap this into a method returning a task is:

public Task<string> GetStringFromUrl(string url)
{
     var t = new TaskCompletionSource<string>();

     GetStringFromUrl(url, s => t.TrySetResult(s));

     return t.Task;
}

这是做到这一点的唯一途径？

Is this the only way to accomplish this?

和有没有办法来包装任务本身的调用GetStringFromUrl（URL，回调）（即调用本身将任务，而不是同步内运行）

And is there a way to wrap the call to GetStringFromUrl(url,callback) in the task itself (i.e. the call itself would run inside the task instead of synchronously)

推荐答案

您code是短的，可读的，高效的，所以我不明白你为什么要寻找替代品，但我想不出什么。我觉得你的做法是合理的。

Your code is short, readable and efficient, so I don't understand why are you looking for alternatives, but I can't think of anything. I think your approach is reasonable.

我也不清楚为什么你认为同步部分是原来的版本不错，但要避免它在工作为主的之一。如果你想同步某些部分可能要花很长时间，解决它的方法的两个版本。

I'm also not sure why do you think that the synchronous part is okay in the original version, but you want to avoid it in the Task-based one. If you think the synchronous part might take too long, fix it for both versions of the method.

但是，如果你希望异步运行（即在线程池）仅在工作的版本，你可以使用<一个href=\"http://msdn.microsoft.com/en-us/library/hh194918%28v=vs.110%29\"><$c$c>Task.Run():

But if you want to run it asynchronously (i.e. on the ThreadPool) only in the Task version, you can use Task.Run():

public Task<string> GetStringFromUrl(string url)
{
    return Task.Run(() =>
    {
        var t = new TaskCompletionSource<string>();

        GetStringFromUrl(url, s => t.TrySetResult(s));

        return t.Task;
    });
}

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