C# to call WebApi implementation

private void button1_Click(object sender, EventArgs e)
        {
           string ss= HttpPost("http://localhost:41558/api/Demo/PostXXX", "{Code:\"test089\",Name:\"test1\"}");
        }

        public static string HttpPost(string url, string body)
        {
            // = new RemoteCertificateValidationCallback(CheckValidationResult);
            Encoding encoding = Encoding.UTF8;
            HttpWebRequest request = (HttpWebRequest)(url);
             = "POST";
             = "text/html, application/xhtml+xml, */*";
             = "application/json";
       
            byte[] buffer = (body);
             = ;
            ().Write(buffer, 0, );
            HttpWebResponse response = (HttpWebResponse)();
            using (StreamReader reader = new StreamReader((), Encoding.UTF8))
            {
                return ();
            }
        }

private void button1_Click(object sender, EventArgs e)
        {
            string ss = HttpGet("http://localhost:41558/api/Demo/GetXXX?Name=Beijing");        }

        public static string HttpGet(string url)
        {
            // = new RemoteCertificateValidationCallback(CheckValidationResult);
            Encoding encoding = Encoding.UTF8;
            HttpWebRequest request = (HttpWebRequest)(url);
             = "GET";
             = "text/html, application/xhtml+xml, */*";
             = "application/json";
           
            HttpWebResponse response = (HttpWebResponse)();
            using (StreamReader reader = new StreamReader((), Encoding.UTF8))
            {
                return ();
            }
        }

private async void button2_Click(object sender, EventArgs e)
{
     HttpClient client = new HttpClient();
     //Deliver Method is issued by HttpClient     HttpResponseMessage response = await ("http://localhost:41558/api/Demo"+"/1");
     if ()
         ("success");
}

private async void button3_Click(object sender, EventArgs e)
{
     //Create a DataContractJsonSerializer that handles serialization     DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(People));
     MemoryStream ms = new MemoryStream();
     //Write the data to MemoryStream     (ms, new People() { Id = 1, Name = "Hello ni" });
     //Be sure to set Position here      = 0;
     HttpContent content = new StreamContent(ms);//Convert MemoryStream to HttpContent      = new ("application/json");
     HttpClient client = new HttpClient();
     // Issue Put Method by HttpClient     HttpResponseMessage response = await ("http://localhost:41558/api/Demo"+ "/1", content);
     if ()
         ("success");
}

using (WebClient client = new WebClient())
{
     ["Type"] = "GET";
     ["Accept"] = "application/json";
      = Encoding.UTF8;
      += (senderobj, es) =>
     {
         var obj = ;
     };
     ("http://localhost:41558/api/Demo");
}