Weird behavior of HttpClient uploading file via PostAsync

Question

I hope someone has an explanation to this, because it drives me nuts.

I have the following code in a WinForms application to upload a file using HttpClient to a Web API service.

ProgressMessageHandler progressMsgHandler = new ProgressMessageHandler();
progressMsgHandler.HttpSendProgress += (s, e) =>
{
   this.InvokeIfNeeded(() =>
   {
      // LOG
      this.AddLogLine("Progress: " + e.ProgressPercentage.ToString());
    });
};

using (var client = HttpClientFactory.Create(progressMsgHandler))
{ 
   using (var content = new MultipartFormDataContent())
   {
      var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
      var streamContent = new StreamContent(stream);
      content.Add(streamContent);

      var url = String.Format("{0}?src={1}", STR_URL_FILEMGMT, "IM");
      client.PostAsync(new Uri(url), content).ContinueWith(task =>
      {
        if (task.Result.IsSuccessStatusCode)
         {
            this.InvokeIfNeeded(() =>
            {
               // LOG
               this.AddLogLine("File has been uploaded OK!");
            });
         }
         else
            this.InvokeIfNeeded(() =>
            {
               // LOG
               this.AddLogLine(String.Format("Error during upload: '{0}'", task.Exception.Message));
            });                                
      });
   }
}

Please note, entire code listed is also wrapped into a try catch where exception would be printed, if any.

Very weird to me is that I don't get any log line printed at all. Neither for progress, neither for posting with success, neither for posting with errors nor in the global try catch.

During debug, I see the code executing, but doesn't hit any breakpoints where the log lines are.

Probably I don't use correctly HttpClient or these tasks (I am beginner at this btw)? Does anyone know what's going wrong with my code?

---

UPDATE (after getting the solution from Noseratio):

Extra information which helps me understand that HttpClient does not need to be disposed can be found here

Answer 1

In your code, client.PostAsync returns instantly (while the operation continues in the background). This unwinds both of your using statements, so the HttpClient object gets disposed of before the upload has finished.

If you want to utilize using here, you'd need to use await instead of ContinueWith:

var result = await client.PostAsync(...);
if (result.IsSuccessStatusCode)
{
    // ...
}

If you need to target .NET 4.0 but develop with VS2012+ , you still can use async/await, Microsoft provides the Microsoft.Bcl.Async library for that.