等待操作者只能异步方法中使用 [英] Await operator can only be used within an Async method

问题描述

我试图做一个简单的程序到Visual Studio 2012年。我一般用BackgroundWorkers运行中测试新的.NET异步功能耗时code异步方式，但有时它似乎是一个麻烦的比较操作简单（但价格昂贵）。新的异步修饰符看起来这将是伟大的使用，但不幸的是我似乎无法得到一个简单的测试准备。

I'm trying to make a simple program to test the new .NET async functionality within Visual Studio 2012. I generally use BackgroundWorkers to run time-consuming code asynchronously, but sometimes it seems like a hassle for a relatively simple (but expensive) operation. The new async modifier looks like it would be great to use, but unfortunately I just can't seem to get a simple test going.

下面是我的code，在C＃控制台应用程序：

Here's my code, in a C# console application:

static void Main(string[] args)
{
    string MarsResponse = await QueryRover();
    Console.WriteLine("Waiting for response from Mars...");
    Console.WriteLine(MarsResponse);
    Console.Read();
}

public static async Task<string> QueryRover()
{
    await Task.Delay(5000);
    return "Doin' good!";
}

我检查了MSDN上的一些例子，它看起来对我来说，这个code应该是工作，而是我对包含该行收到生成错误等待QueryRover（）;我是不是疯了还是有鬼发生？

I checked out some examples on MSDN and it looks to me like this code should be working, but instead I'm getting a build error on the line containing "await QueryRover();" Am I going crazy or is something fishy happening?

推荐答案

您只能使用等待在异步方法，和 主不能异步 。

You can only use await in an async method, and Main cannot be async.

您将不得不使用自己的异步兼容的情况下，调用等待在返回工作在主的方法，或者忽略返回工作和公正阻塞调用读。需要注意的是等待将包装中的任何异常的 AggregateException 。

You'll have to use your own async-compatible context, call Wait on the returned Task in the Main method, or just ignore the returned Task and just block on the call to Read. Note that Wait will wrap any exceptions in an AggregateException.

如果你想有一个很好的介绍，请参阅我的<一个href="http://blog.stephencleary.com/2012/02/async-and-await.html"><$c$c>async/<$c$c>await开场后。

If you want a good intro, see my async/await intro post.

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