Methode PostRequest

        // Methode post request
        async void PostRequest()
        {
            IEnumerable<KeyValuePair<string, string>> queries = new List<KeyValuePair<string, string>>()
            {
                new KeyValuePair<string,string>("query1","Abdessalam"),
                new KeyValuePair<string,string>("query2","Kilya")
            };
            HttpContent q = new FormUrlEncodedContent(queries);
            using (HttpClient client = new HttpClient())
            {
                using (HttpResponseMessage response = await client.PostAsync("https://posttestserver.com/post.php", q))
                {
                    using (HttpContent content = response.Content)
                    {
                        string mycontent = await content.ReadAsStringAsync();
                        Console.WriteLine(mycontent);
                    }
                }
            }
        }