C# 使用 HttpWebRequest.GetResponseAsync 异步和等待
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Async and Await with HttpWebRequest.GetResponseAsync
提问by John Koerner
I am trying to use Async and Await when making a web request and am finding that it never gets past the await line. I am doing this from a Metro app, but I also verified the problem in a winforms app.
我在发出 Web 请求时尝试使用 Async 和 Await，但我发现它永远不会超过 await 线。我是通过 Metro 应用程序执行此操作的，但我也在 winforms 应用程序中验证了该问题。
public async Task<string> DoSomething()
{
string url = "http://imgur.com/gallery/VcBfl.json";
HttpWebRequest request = HttpWebRequest.CreateHttp(url);
var ws = await request.GetResponseAsync();
return ws.ResponseUri.ToString(); ;
}
If I don't use await and instead perform a synchronous wait, it works, but I need this to run asynchronously.
如果我不使用 await 而是执行同步等待，它可以工作，但我需要它异步运行。
What am I missing in this code that is causing the await to never return?
我在这段代码中遗漏了什么导致等待永远不会返回？
采纳答案by Stephen Cleary
I suspect that further up your call stack, you're either calling Waitor Resulton the returned Task. This will cause a deadlock, as I describe on my blog.
我怀疑在你的调用堆栈上，你要么调用Wait要么Result在返回的Task. 这将导致僵局，正如我在我的博客中所描述的。
Follow these best practices to avoid the deadlock:
请遵循以下最佳实践来避免死锁：
- Don't block on
asynccode; useasyncall the way down. - In your "library" methods, use
ConfigureAwait(false).
- 不要阻塞
async代码；一直使用async下去。 - 在您的“库”方法中，使用
ConfigureAwait(false).
