任务和线程在Asp.Net调度 [英] Tasks and Thread Scheduling in Asp.Net

问题描述

在一个Asp.Net网页按钮，点击下面我有code

  // $ C $，C是Asp.Net工作线程运行
VAR的HttpClient =新的HttpClient（）;
VAR任务= httpClient.GetAsync（/ someapiCall）; //创建一个新的线程，并在其上​​执行
task.Wait（）;
 

现在，当我打电话task.Wait会发生什么工作线程？

1. 会不会是挂起状态，等待HttpClient的调用完成？
2. 它会被返回到线程池，可用于处理其他请求？

有没有之间的上述code和下面的

有什么区别

  VAR的HttpClient =新的HttpClient（）;
VAR任务= httpClient.GetAsync（/ someapiCall）; //创建一个新的线程，并在其上​​执行
ManualResetEvent的MRE =新的ManualResetEvent（假）;
task.ContinueWith（（吨）=＆GT; {mre.Set（）;}）;
mre.WaitOne（）;
 

解决方案

您的线程将被阻塞同步等待操作完成在这两种情况下。它不会返回到线程池。

目前使用等待或隐含的由等待一个<$没有区别，如果你阻止的明确的C $ C>的ManualResetEvent 将异步操作后设置完成。

在一个异步操作阻止同步可能导致用户界面环境（和其他情况下的死锁，其中有一个的SynchronizationContext ，如ASP.Net）

要不会阻止你应该使用线程异步等待：

 等待新的HttpClient（）GetAsync（/ someapiCall）。
 

In a Asp.Net Web page button click I have below code

//Code is running on Asp.Net worker Thread
var httpClient = new HttpClient();
var task = httpClient.GetAsync("/someapiCall");  //Creates a new thread and executed on it
task.Wait();

Now when I call task.Wait what will happen to the worker thread?

1. Will it be in suspended state waiting for the httpClient call to complete?
2. Will it be returned to thread pool and be available to process other requests?

Is there any difference between the above code and the below

var httpClient = new HttpClient();
var task = httpClient.GetAsync("/someapiCall");  //Creates a new thread and executed on it
ManualResetEvent mre = new ManualResetEvent(false);
task.ContinueWith((t) => { mre.Set(); });
mre.WaitOne();

解决方案

Your thread will be blocked synchronously waiting for the operation to complete in both cases. It will not go back to the ThreadPool.

There's no difference if you're blocking explicitly by using Wait or implicitly by waiting on a ManualResetEvent that would be set after the asynchronous operation completes.

Blocking synchronously on an async operation can lead to deadlocks in UI environments (and other cases where there's a SynchronizationContext, i.e. ASP.Net)

To not block that thread you should be using async-await:

await new HttpClient().GetAsync("/someapiCall");

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