在异步MSDN例如/等待 - 我不能在电话的await后达到破发点？ [英] MSDN example on async/await - can't I reach the break point after the await call?

问题描述

在试图MSDN对异步例如/ AWAIT，我为什么不能在运营商的await后达到一个破发点？

In trying MSDN's example on async/await, why I can't reach a break point after the await operator ?

private static void Main(string[] args)
{
    AccessTheWebAsync();
}

private async Task<int> AccessTheWebAsync()
{ 
    // You need to add a reference to System.Net.Http to declare client.
    HttpClient client = new HttpClient();

    // GetStringAsync returns a Task<string>. That means that when you await the
    // task you'll get a string (urlContents).
    Task<string> getStringTask = client.GetStringAsync("http://msdn.microsoft.com");

    // You can do work here that doesn't rely on the string from GetStringAsync.
    /*** not relevant here ***/
    //DoIndependentWork();

    // The await operator suspends AccessTheWebAsync.
    //  - AccessTheWebAsync can't continue until getStringTask is complete.
    //  - Meanwhile, control returns to the caller of AccessTheWebAsync.
    //  - Control resumes here when getStringTask is complete. 
    //  - The await operator then retrieves the string result from getStringTask.
    string urlContents = await getStringTask;

    // The return statement specifies an integer result.
    // Any methods that are awaiting AccessTheWebAsync retrieve the length value.
    return urlContents.Length;
}

我的理解是，AWAIT是从抽象开发商异步流结构 - 让他/她，仿佛同步工作。换句话说，在上述code，我不关心如何以及何时 getStringTask 结束，我只关心它完成，并使用其结果。我希望再能够在某个时候达到的await调用后破发点。

My understanding is that the await is a construct that abstracts the asynchronous flow from the developer - leaving him/her as if working synchronously. In other words, in the code above, I do not care about how and when the getStringTask finishes, I care only about it finishing and using its results. I would expect then to be able to reach the break point after the await call at sometime.

推荐答案

您调用从控制台应用程序的主要方法，你的异步方法，无需等待异步方法来完成。这样一来，你的进程终止之前你的任务有机会完成。

You call your asynchronous method from a Console application's Main method without waiting for the async method to finish. As a result, your process terminates before your task has a chance to complete.

既然你不能转换控制台应用程序的主到异步（异步任务）的方法，你必须阻止对异步方法，通过调用等待或。结果：

Since you can't convert a Console application's Main to an asynchronous (async Task) method, you'll have to block on the asynchronous method, by calling Wait or .Result:

private static void Main(string[] args)
{ 
    AccessTheWebAsync().Wait();
}

或

private static void Main(string[] args)
{ 
    var webTask=AccessTheWebAsync();
    //... do other work until the resuls is actually needed
    var pageSize=webTask.Result;
    //... now use the returned page size
}

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