PostAsync crashes

Hi, in the following code, I want to send the data via a post service but the app crashes. Here is the code from App.Xaml.cs. Help will be appreciated !!

{

        string requestUri = "http://xxxxxxxxxxxxxxxxxxxx";


        var uri = new Uri(string.Format(requestUri, string.Empty));

        try
        {


            using (var client = new HttpClient())
            using (var content = new MultipartFormDataContent())
            {
                var values = new[]
                    {
                    new KeyValuePair<string, string>("Language","en"),
                    new KeyValuePair<string, string>("Platform","Android"),
                     new KeyValuePair<string, string>("Title","abc123")




                    };

                foreach (var keyValuePair in values)
                    content.Add(new StringContent(keyValuePair.Value), keyValuePair.Key);

                using (var result = await client.PostAsync(uri, content))
                {
                    var input = await result.Content.ReadAsStringAsync();

                    if (result.IsSuccessStatusCode)
                    {
                        MainPage = new App1.MainPage();
                    }
                    else
                    {
                      //do nothing
                    }
                }
            }
        }

        catch (Exception ex)
        {
            Debug.WriteLine("Failed to submit");
        }

}