Exception in HttpResponseMessage for async POST method.

Question

HI

This exception is bothering me since many days now. I am trying to send a POST call to a Last.fm API method. But whenever I send a call, I get the following exception -  "An exception of type 'System.Net.Http.HttpRequestException' occurred in mscorlib.dll but was not handled in user code".
Additional information: An error occurred while sending the request. If I print out the exception it says -

System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.WebException: The underlying connection was closed: The connection was closed unexpectedly.

My GET calls to the authentication API of last.fm are working fine.

I am attaching a code snippet:

private async void Collection_Click_1(object sender, RoutedEventArgs e)
        {
/* .
   .
   .
*/

HttpClient Cli = new HttpClient();
string track_updateNowPlaying = "method=track.updateNowPlaying&track=" + id3.Title + "&artist=" +id3.Artist + "&album=" + id3.Album + "&api_key=" + lfm_api_key + "&api_sig=" + updtrack_sig + "&sk=" + Globalv.session_key;

HttpContent tunp =new StringContent(track_updateNowPlaying);

try
{
    //getting exception in the following line
    HttpResponseMessage upd_now_playing = await cli.PostAsync(new Uri("http://ws.audioscrobbler.com/2.0/", UriKind.RelativeOrAbsolute), tunp);

}
catch(Exception ex) {textblock.text = ex.ToString();}
}

private async void LoginBtn_Click_1(object sender, RoutedEventArgs e) //this function is called before collection_click_1 function
{
/* .
   .
   .
*/
    HttpClient cli = new HttpClient();
    string auth_request = "http://ws.audioscrobbler.com/2.0/?method=auth.getMobileSession&username=" + UsernameTBx.Text + "&authToken=" + lfm_authToken + "&api_key=" + lfm_api_key + "&api_sig=" + lfm_api_sig;

    HttpResponseMessage auth = await cli.GetAsync(auth_request); //this works fine...

}

Need some help here.

---

-Sagar

Answer 1

Can you send a reproduction app to me?  MSMALL at Microsoft

---

Matt Small - Microsoft Escalation Engineer - Forum Moderator

Answer 2

Hi

I guess I figured it out. I'm keeping the post for others to refer.

The case was that Last.fm servers do not accept Expect:100Continue in the header field. So I had to explicitly change it to false. Last.fm hasn't mentioned this issue clearly in their documentation. Took long to figure out...

Had to add the following:

HttpClient cli = new HttpClient();
cli.DefaultRequestHeaders.ExpectContinue = false;

---

-Sagar