Xamarin Android HttpClient PostAsync

Question

I have an android app in Xamarin native. I am trying to consume a Restful service from an API in another server.

I have this:

private async Task<string> CreateCellphone(string url, Cellphone cell)
        {
            string cellphone = JsonConvert.SerializeObject(cell);
            HttpContent content = new StringContent(cellphone, Encoding.UTF8, "application/json");
            using (HttpClient client = new HttpClient())
            {
                HttpResponseMessage response = await client.PostAsync(url, content);
                string responseMessage = await response.Content.ReadAsStringAsync();
                return responseMessage;
            }
        }

I execute this on a button call like this:

private void RegisterButtonOnClick(object sender, EventArgs e)
        {
            // Create new GUID
            Guid obj = Guid.NewGuid();

            // Store the created GUID in a private shared preferences file
            var localGUID = Application.Context.GetSharedPreferences("LocalSetup", FileCreationMode.Private);
            var guidEdit = localGUID.Edit();
            guidEdit.PutString("GUID", obj.ToString());
            guidEdit.PutBoolean("IsRegistered", true);
            guidEdit.Commit();

            // Create the cellphone record into the database for DB admin to activate
            _url = Resources.GetString(Resource.String.cellphone_api_url);
            Cellphone cell = new Cellphone();
            cell.CellphoneId = obj.ToString();
            var response = CreateCellphone(_url, cell);                
        }

But when my code gets to the postAsync method, nothing happens, it just continues without actually sending the code to the endpoint, I have no idea what I might be doing wrong, because all documentation I have on PostAsync tells me this is how to send json data for a Restful Web api endpoint.

Thank you in advance for any pointers.

score 1 · Accepted Answer · answered Jul 21 '17 at 15:25

You need to await the call to CreateCellphone or nothing will happen because the response Task will get disposed of almost immediately. Not sure if you can make your button click method async in Xamarin, but I would try this:

private async void RegisterButtonOnClick(object sender, EventArgs e)
      //^^^^^
      //Add this
{
    //snip

    await CreateCellphone(_url, cell);
}

Failing that, there are various way to call an async method synchronously, check this question.

I used to async methods, now I just execute the async on the actual request and it works like a charm, thank you! — V. Benavides, Jul 25 '17 at 02:09

Xamarin Android HttpClient PostAsync

1 Answers1