问题描述
这是最小可能的场景,我能够准备:
This is the smallest possible scenario, I was able to prepare:
- 此代码连接到 imap.gmail.com
- 读取初始服务器问候语(使用 Read 方法)
- 发送 NOOP 命令(无操作)
- 读取 NOOP 命令响应(再次使用 Read 方法)
问题在于第二次读取挂起.如果使用'await ReadAsync',它可以完美运行.
The problem is that the second Read hangs. It works perfectly if 'await ReadAsync' is used.
当我中断程序时,我可以看到调用堆栈从 task.Wait() 开始并在 System.Threading.Monitor.Wait() 结束.
When I break the program I can see the Call Stack starts at task.Wait() and ends on System.Threading.Monitor.Wait().
如果我一步一步调试它,它不会挂起.我必须承认它看起来像一个 .NET 框架错误,但也许我遗漏了一些明显的东西.
If I debug this step by step, it does not hang. I must admit it looks like a .NET framework bug, but maybe I'm missing something obvious.
private static async Task<byte[]> ReadAsync(StreamSocket socket)
{
// all responses are smaller that 1024
IBuffer buffer = new byte[1024].AsBuffer();
await socket.InputStream.ReadAsync(
buffer, buffer.Capacity, InputStreamOptions.Partial);
return buffer.ToArray();
}
private static byte[] Read(StreamSocket socket)
{
Task<byte[]> task = ReadAsync(socket);
task.Wait();
return task.Result;
}
private async void Button_Click(object sender, RoutedEventArgs e)
{
Encoding encoding = Encoding.GetEncoding("Windows-1250");
using (StreamSocket socket = new StreamSocket())
{
await socket.ConnectAsync(
new HostName("imap.gmail.com"), "993", SocketProtectionLevel.Ssl);
// notice we are using Wait() version here without any problems:
byte[] serverGreetings = Read(socket);
await socket.OutputStream.WriteAsync(
encoding.GetBytes("A0001 NOOP\r\n").AsBuffer());
await socket.OutputStream.FlushAsync();
//byte[] noopResponse = await ReadAsync(socket); // works
byte[] noopResponse = Read(socket); // hangs
}
}
推荐答案
我解释了这个僵局的原因 在我最近的 MSDN 文章 以及 在我的博客上.
I explain the cause of this deadlock in my recent MSDN article as well as on my blog.
简短的回答是,您不应该在async
代码上调用Wait
或Result
;你应该一直使用 await
.
The short answer is that you're not supposed to call Wait
or Result
on async
code; you should use await
all the way.
这篇关于StreamSocket.InputStreamOptions.ReadAsync 在使用 Wait() 时挂起的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!