AggregateException is throwing while waiting for PostAsJsonAsync

Question

AggregateException is throwing while waiting for API post to complete how i could fix this?

My API call is similar like this

using (var httpClient = new HttpClient())
{
    httpClient.BaseAddress = new Uri(workflowUrl);
    var task = httpClient.PostAsJsonAsync("api/apiname/execute/", executeModel)
                             .ContinueWith(x => x.Result.Content.ReadAsAsync<bool>().Result);

    Task continuation = task.ContinueWith(x =>
    {
        bool response = x.Result;
    });
    continuation.Wait(); 

}

I am getting Exception given below while waitng for POST to complete.

  System.AggregateException was caught
  Message=One or more errors occurred.
  Source=mscorlib
  StackTrace:
       at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
       at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
       at System.Threading.Tasks.Task.Wait()
       at 
  InnerException: System.AggregateException
       Message=One or more errors occurred.
       Source=mscorlib
       StackTrace:
            at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
            at System.Threading.Tasks.Task`1.get_Result()
            at 
            at System.Threading.Tasks.Task`1.<>c__DisplayClass17.<ContinueWith>b__16(Object obj)
            at System.Threading.Tasks.Task.InnerInvoke()
            at System.Threading.Tasks.Task.Execute()
       InnerException: System.AggregateException
            Message=One or more errors occurred.
            Source=mscorlib
            StackTrace:
                 at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
                 at System.Threading.Tasks.Task`1.get_Result()
                 at WebUI.ListController.<ListRepeater_ItemCommand>b__f(Task`1 x) in PostAsJsonAsync:line 741
                 at System.Threading.Tasks.Task`1.<>c__DisplayClass1a`1.<ContinueWith>b__19()
                 at System.Threading.Tasks.Task`1.InvokeFuture(Object futureAsObj)
                 at System.Threading.Tasks.Task.InnerInvoke()
                 at System.Threading.Tasks.Task.Execute()
            InnerException: System.Threading.Tasks.TaskCanceledException
                 Message=A task was canceled.
                 InnerException:

Answer 1

Are you posting a big piece of data ? Once I had a similar issue. I believe the underlying problem is occasional timeout due to bandwidth issues. I tried getting the task and manually waiting on it then checking .IsFaulted and .IsCancelled but the .Result throws AggregateException / TaskCancelledException.

Maybe you should try to increase HttpClient.Timeout property which is 100 sec by default ?