C# 传入已取消的CancellationToken会导致HttpClient挂起

我想使用

CancellationToken

取消对

HttpClient.PostAsJsonAsync

的呼叫。但是，通过以下设置，对

PostAsJsonAsync

的调用将无限期挂起（我让它运行了几分钟）

---

这显然是您遇到的一个bug，您可以通过自己构建HttpContent/ObjectContent对象来解决它，如下所示

CancellationTokenSource source = new CancellationTokenSource();
source.Cancel();
HttpClient client = new HttpClient();

var content = new ObjectContent(typeof (MyObject), new MyObject(), new JsonMediaTypeFormatter());
content.LoadIntoBufferAsync().Wait();
try
{
    var task = client.PostAsync("http://server-address.com",content, source.Token);

    task.Wait();
}
catch (Exception ex)
{
    //This will get hit now with an AggregateException containing a TaskCancelledException.
}

---

调用

content.LoadIntoBufferAsync

会强制在PostAsync之前进行反序列化，似乎可以避免死锁。

同意@Darrel Miller的回答。这是一个错误。只是为bug报告添加更多细节

问题在于，内部使用了

TaskCompletionSource

，但在这种特定情况下，由于取消而引发异常时，它不会被捕获，并且

TaskCompletionSource

从未设置为一种已完成状态（因此，等待

TaskCompletionSource

的

任务将永远不会返回

使用ILSpy，查看
HttpClientHandler.SendAsync
，您可以看到
TaskCompletionSource
：

// System.Net.Http.HttpClientHandler
/// <summary>Creates an instance of  <see cref="T:System.Net.Http.HttpResponseMessage" /> based on the information provided in the <see cref="T:System.Net.Http.HttpRequestMessage" /> as an operation that will not block.</summary>
/// <returns>Returns <see cref="T:System.Threading.Tasks.Task`1" />.The task object representing the asynchronous operation.</returns>
/// <param name="request">The HTTP request message.</param>
/// <param name="cancellationToken">A cancellation token to cancel the operation.</param>
/// <exception cref="T:System.ArgumentNullException">The <paramref name="request" /> was null.</exception>
protected internal override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
    if (request == null)
    {
        throw new ArgumentNullException("request", SR.net_http_handler_norequest);
    }
    this.CheckDisposed();
    if (Logging.On)
    {
        Logging.Enter(Logging.Http, this, "SendAsync", request);
    }
    this.SetOperationStarted();
    TaskCompletionSource<HttpResponseMessage> taskCompletionSource = new TaskCompletionSource<HttpResponseMessage>();
    HttpClientHandler.RequestState requestState = new HttpClientHandler.RequestState();
    requestState.tcs = taskCompletionSource;
    requestState.cancellationToken = cancellationToken;
    requestState.requestMessage = request;
    this.lastUsedRequestUri = request.RequestUri;
    try
    {
        HttpWebRequest httpWebRequest = this.CreateAndPrepareWebRequest(request);
        requestState.webRequest = httpWebRequest;
        cancellationToken.Register(HttpClientHandler.onCancel, httpWebRequest);
        if (ExecutionContext.IsFlowSuppressed())
        {
            IWebProxy webProxy = null;
            if (this.useProxy)
            {
                webProxy = (this.proxy ?? WebRequest.DefaultWebProxy);
            }
            if (this.UseDefaultCredentials || this.Credentials != null || (webProxy != null && webProxy.Credentials != null))
            {
                this.SafeCaptureIdenity(requestState);
            }
        }
        Task.Factory.StartNew(this.startRequest, requestState);
    }
    catch (Exception e)
    {
        this.HandleAsyncException(requestState, e);
    }
    if (Logging.On)
    {
        Logging.Exit(Logging.Http, this, "SendAsync", taskCompletionSource.Task);
    }
    return taskCompletionSource.Task;
}

您会注意到，调用
ContinueWithStandard
中的委托在委托内没有异常处理，并且没有人保留返回的任务（因此，当此任务引发异常时，它将被忽略）。调用
this.StartGettingRequestStream（state）；
会引发异常：

System.Net.WebException occurred
  HResult=-2146233079
  Message=The request was aborted: The request was canceled.
  Source=System
  StackTrace:
       at System.Net.HttpWebRequest.BeginGetRequestStream(AsyncCallback callback, Object state)
  InnerException: 

>   System.dll!System.Net.HttpWebRequest.BeginGetRequestStream(System.AsyncCallback callback, object state) Line 1370   C#
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.StartGettingRequestStream(System.Net.Http.HttpClientHandler.RequestState state) + 0x82 bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.PrepareAndStartContentUpload.AnonymousMethod__0(System.Threading.Tasks.Task task) + 0x92 bytes    
    mscorlib.dll!System.Threading.Tasks.ContinuationTaskFromTask.InnerInvoke() Line 59 + 0xc bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.Execute() Line 2459 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) Line 2815 + 0x9 bytes C#
    mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 581 + 0xd bytes  C#
    mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 530 + 0xd bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) Line 2785  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) Line 2728   C#
    mscorlib.dll!System.Threading.Tasks.ThreadPoolTaskScheduler.TryExecuteTaskInline(System.Threading.Tasks.Task task, bool taskWasPreviouslyQueued) Line 91 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.TaskScheduler.TryRunInline(System.Threading.Tasks.Task task, bool taskWasPreviouslyQueued) Line 221 + 0x12 bytes    C#
    mscorlib.dll!System.Threading.Tasks.TaskContinuation.InlineIfPossibleOrElseQueue(System.Threading.Tasks.Task task, bool needsProtection) Line 259 + 0xe bytes   C#
    mscorlib.dll!System.Threading.Tasks.StandardTaskContinuation.Run(System.Threading.Tasks.Task completedTask, bool bCanInlineContinuationTask) Line 334 + 0xc bytes   C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWithCore(System.Threading.Tasks.Task continuationTask, System.Threading.Tasks.TaskScheduler scheduler, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions options) Line 4626 + 0x12 bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWith(System.Action<System.Threading.Tasks.Task> continuationAction, System.Threading.Tasks.TaskScheduler scheduler, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions continuationOptions, ref System.Threading.StackCrawlMark stackMark) Line 3840 C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWith(System.Action<System.Threading.Tasks.Task> continuationAction, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions continuationOptions, System.Threading.Tasks.TaskScheduler scheduler) Line 3805 + 0x1b bytes   C#
    System.Net.Http.dll!System.Net.Http.HttpUtilities.ContinueWithStandard(System.Threading.Tasks.Task task, System.Action<System.Threading.Tasks.Task> continuation) + 0x2c bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.PrepareAndStartContentUpload(System.Net.Http.HttpClientHandler.RequestState state) + 0x16b bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.StartRequest(object obj) + 0x5a bytes 
    mscorlib.dll!System.Threading.Tasks.Task.InnerInvoke() Line 2835 + 0xd bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.Execute() Line 2459 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) Line 2815 + 0x9 bytes C#
    mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 581 + 0xd bytes  C#
    mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 530 + 0xd bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) Line 2785  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) Line 2728   C#
    mscorlib.dll!System.Threading.Tasks.Task.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() Line 2664 + 0x7 bytes   C#
    mscorlib.dll!System.Threading.ThreadPoolWorkQueue.Dispatch() Line 829   C#
    mscorlib.dll!System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() Line 1170 + 0x5 bytes   C#
    [Native to Managed Transition]  

以下是发生异常时的完整调用堆栈：

System.Net.WebException occurred
  HResult=-2146233079
  Message=The request was aborted: The request was canceled.
  Source=System
  StackTrace:
       at System.Net.HttpWebRequest.BeginGetRequestStream(AsyncCallback callback, Object state)
  InnerException: 

>   System.dll!System.Net.HttpWebRequest.BeginGetRequestStream(System.AsyncCallback callback, object state) Line 1370   C#
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.StartGettingRequestStream(System.Net.Http.HttpClientHandler.RequestState state) + 0x82 bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.PrepareAndStartContentUpload.AnonymousMethod__0(System.Threading.Tasks.Task task) + 0x92 bytes    
    mscorlib.dll!System.Threading.Tasks.ContinuationTaskFromTask.InnerInvoke() Line 59 + 0xc bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.Execute() Line 2459 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) Line 2815 + 0x9 bytes C#
    mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 581 + 0xd bytes  C#
    mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 530 + 0xd bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) Line 2785  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) Line 2728   C#
    mscorlib.dll!System.Threading.Tasks.ThreadPoolTaskScheduler.TryExecuteTaskInline(System.Threading.Tasks.Task task, bool taskWasPreviouslyQueued) Line 91 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.TaskScheduler.TryRunInline(System.Threading.Tasks.Task task, bool taskWasPreviouslyQueued) Line 221 + 0x12 bytes    C#
    mscorlib.dll!System.Threading.Tasks.TaskContinuation.InlineIfPossibleOrElseQueue(System.Threading.Tasks.Task task, bool needsProtection) Line 259 + 0xe bytes   C#
    mscorlib.dll!System.Threading.Tasks.StandardTaskContinuation.Run(System.Threading.Tasks.Task completedTask, bool bCanInlineContinuationTask) Line 334 + 0xc bytes   C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWithCore(System.Threading.Tasks.Task continuationTask, System.Threading.Tasks.TaskScheduler scheduler, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions options) Line 4626 + 0x12 bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWith(System.Action<System.Threading.Tasks.Task> continuationAction, System.Threading.Tasks.TaskScheduler scheduler, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions continuationOptions, ref System.Threading.StackCrawlMark stackMark) Line 3840 C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWith(System.Action<System.Threading.Tasks.Task> continuationAction, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions continuationOptions, System.Threading.Tasks.TaskScheduler scheduler) Line 3805 + 0x1b bytes   C#
    System.Net.Http.dll!System.Net.Http.HttpUtilities.ContinueWithStandard(System.Threading.Tasks.Task task, System.Action<System.Threading.Tasks.Task> continuation) + 0x2c bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.PrepareAndStartContentUpload(System.Net.Http.HttpClientHandler.RequestState state) + 0x16b bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.StartRequest(object obj) + 0x5a bytes 
    mscorlib.dll!System.Threading.Tasks.Task.InnerInvoke() Line 2835 + 0xd bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.Execute() Line 2459 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) Line 2815 + 0x9 bytes C#
    mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 581 + 0xd bytes  C#
    mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 530 + 0xd bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) Line 2785  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) Line 2728   C#
    mscorlib.dll!System.Threading.Tasks.Task.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() Line 2664 + 0x7 bytes   C#
    mscorlib.dll!System.Threading.ThreadPoolWorkQueue.Dispatch() Line 829   C#
    mscorlib.dll!System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() Line 1170 + 0x5 bytes   C#
    [Native to Managed Transition]  

>System.dll！System.Net.HttpWebRequest.BeginGetRequestStream（System.AsyncCallback回调，对象状态）第1370 C行#
System.Net.Http.dll！System.Net.Http.HttpClientHandler.StartGettingRequestStream（System.Net.Http.HttpClientHandler.RequestState）+0x82字节
System.Net.Http.dll！System.Net.Http.HttpClientHandler.PrepareAndStartContentUpload.AnonymousMethod_uu0（System.Threading.Tasks.Task任务）+0x92字节
mscorlib.dll！System.Threading.Tasks.ContinuationTaskFromTask.InnerInvoke（）行59+0xc字节#
mscorlib.dll！System.Threading.Tasks.Task.Execute（）行2459+0xb字节C#
mscorlib.dll！System.Threading.Tasks.Task.ExecutionContextCallback（对象obj）行2815+0x9字节C#
mscorlib.dll！System.Threading.ExecutionContext.RunInternal（System.Threading.ExecutionContext ExecutionContext，System.Threading.ContextCallback回调，对象状态，bool preserveSyncCtx）第581行+0xd字节C#
mscorlib.dll！System.Threading.ExecutionContext.Run（System.Threading.ExecutionContext ExecutionContext，System.Threading.ContextCallback回调，对象状态，bool preserveSyncCtx）第530+0xd字节C#
mscorlib.dll！System.Threading.Tasks.Task.ExecuteWithThreadLocal（参考System.Threading.Tasks.Task currentTaskSlot）行2785 C#
mscorlib.dll！System.Threading.Tasks.Task.ExecuteEntry（bool bPreventDoubleExecution）行2728 C#
mscorlib.dll！System.Threading.Tasks.ThreadPoolTaskScheduler.TryExecuteTaskInline（System.Threading.Tasks.Task任务，bool taskWasPreviouslyQueued）行91+0xb字节C#
mscorlib.dll！System.Threading.Tasks.TaskScheduler.TryRunLine（System.Threading.Tasks.Task Task，bool taskWasPreviouslyQueued）行221+0x12字节C#
mscorlib.dll！System.Threading.Tasks.TaskContinuation.InlineIfPossibleRelSequeue（System.Threading.Tasks.Task Task，bool needsProtection）行259+0xe字节C#
mscorlib.dll！System.Threading.Tasks.StandardTaskContinuation.Run（System.Threading.Tasks.Task completedTask，bool bcanilineContinuationTask）第334行+0xc字节#
mscorlib.dll！System.Threading.Tasks.Task.ContinueWithCore（System.Threading.Tasks.Task continuationTask，System.Threading.Tasks.TaskScheduler调度程序，System.Threading.CancellationToken CancellationToken，System.Threading.Tasks.TaskContinuationOptions）第4626行+0x12字节C#
mscorlib.dll！System.Threading.Tasks.Task.ContinueWith（System.Action continuationAction，System.Threading.Tasks.TaskScheduler调度程序，System.Threading.CancellationToken CancellationToken，System.Threading.TaskContinuationOptions continuationOptions，参考System.Threading.StackCrawlMark stackMark）第3840 C行#
mscorlib.dll！System.Threading.Tasks.Task.ContinueWith（System.Action continuationAction，System.Threading.CancellationToken CancellationToken，System.Threading.TaskContinuationOptions continuationOptions，System.Threading.Tasks.TaskScheduler调度程序）行3805+0x1b字节C#
System.Net.Http.dll！System.Net.Http.HttpUtilities.ContinueWithStandard（System.Threading.Tasks.Task任务，System.Action continuation）+0x2c字节
System.Net.Http.dll！System.Net.Http.HttpClientHandler.PrepareAndStartContentUpload（System.Net.Http.HttpClientHandler.RequestState）+0x16b字节
System.Net.Http.dll！System.Net.Http.HttpClientHandler.StartRequest（objectobj）+0x5a字节
mscorlib.dll！System.Threading.Tasks.Task.InnerInvoke（）行2835+0xd字节C#
mscorlib.dll！System.Threading.Tasks.Task.Execute（）行2459+0xb字节C#
mscorlib.dll！System.Threading.Tasks.Task.ExecutionContextCallback（对象obj）行2815+0x9字节C#
mscorlib.dll！System.Threading.ExecutionContext.RunInternal（System.Threading.ExecutionContext ExecutionContext，System.Threading.ContextCallback回调，对象状态，bool preserveSyncCtx）第581行+0xd字节C#
mscorlib.dll！System.Threading.ExecutionContext.Run（System.Threading.ExecutionContext ExecutionContext，System.Threading.ContextCallback回调，对象状态，bool preserveSyncCtx）第530+0xd字节C#
mscorlib.dll！System.Threading.Tasks.Task.ExecuteWithThreadLocal（参考System.Threading.Tasks.Task currentTaskSlot）行2785 C#
mscorlib.dll！System.Threading.Tasks.Task.ExecuteEntry（bool bPreventDoubleExecution）行2728 C#
mscorlib.dll！System.Threading.Tasks.Task.System.Threadi
>   System.dll!System.Net.HttpWebRequest.BeginGetRequestStream(System.AsyncCallback callback, object state) Line 1370   C#
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.StartGettingRequestStream(System.Net.Http.HttpClientHandler.RequestState state) + 0x82 bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.PrepareAndStartContentUpload.AnonymousMethod__0(System.Threading.Tasks.Task task) + 0x92 bytes    
    mscorlib.dll!System.Threading.Tasks.ContinuationTaskFromTask.InnerInvoke() Line 59 + 0xc bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.Execute() Line 2459 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) Line 2815 + 0x9 bytes C#
    mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 581 + 0xd bytes  C#
    mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 530 + 0xd bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) Line 2785  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) Line 2728   C#
    mscorlib.dll!System.Threading.Tasks.ThreadPoolTaskScheduler.TryExecuteTaskInline(System.Threading.Tasks.Task task, bool taskWasPreviouslyQueued) Line 91 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.TaskScheduler.TryRunInline(System.Threading.Tasks.Task task, bool taskWasPreviouslyQueued) Line 221 + 0x12 bytes    C#
    mscorlib.dll!System.Threading.Tasks.TaskContinuation.InlineIfPossibleOrElseQueue(System.Threading.Tasks.Task task, bool needsProtection) Line 259 + 0xe bytes   C#
    mscorlib.dll!System.Threading.Tasks.StandardTaskContinuation.Run(System.Threading.Tasks.Task completedTask, bool bCanInlineContinuationTask) Line 334 + 0xc bytes   C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWithCore(System.Threading.Tasks.Task continuationTask, System.Threading.Tasks.TaskScheduler scheduler, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions options) Line 4626 + 0x12 bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWith(System.Action<System.Threading.Tasks.Task> continuationAction, System.Threading.Tasks.TaskScheduler scheduler, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions continuationOptions, ref System.Threading.StackCrawlMark stackMark) Line 3840 C#
    mscorlib.dll!System.Threading.Tasks.Task.ContinueWith(System.Action<System.Threading.Tasks.Task> continuationAction, System.Threading.CancellationToken cancellationToken, System.Threading.Tasks.TaskContinuationOptions continuationOptions, System.Threading.Tasks.TaskScheduler scheduler) Line 3805 + 0x1b bytes   C#
    System.Net.Http.dll!System.Net.Http.HttpUtilities.ContinueWithStandard(System.Threading.Tasks.Task task, System.Action<System.Threading.Tasks.Task> continuation) + 0x2c bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.PrepareAndStartContentUpload(System.Net.Http.HttpClientHandler.RequestState state) + 0x16b bytes  
    System.Net.Http.dll!System.Net.Http.HttpClientHandler.StartRequest(object obj) + 0x5a bytes 
    mscorlib.dll!System.Threading.Tasks.Task.InnerInvoke() Line 2835 + 0xd bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.Execute() Line 2459 + 0xb bytes    C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) Line 2815 + 0x9 bytes C#
    mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 581 + 0xd bytes  C#
    mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 530 + 0xd bytes  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) Line 2785  C#
    mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) Line 2728   C#
    mscorlib.dll!System.Threading.Tasks.Task.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() Line 2664 + 0x7 bytes   C#
    mscorlib.dll!System.Threading.ThreadPoolWorkQueue.Dispatch() Line 829   C#
    mscorlib.dll!System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() Line 1170 + 0x5 bytes   C#
    [Native to Managed Transition]