var user = new UserJson
{ 
Name = "Vladimir", 
Age = 21 
}; 
var jsonData = JsonConvert.SerializeObject(user); 

JsonWiew.Text = jsonData; 

var request = (HttpWebRequest)WebRequest.Create("мой web - сервер(здесь адрес главной страницы)";); 
var data = Encoding.ASCII.GetBytes(jsonData); 

request.Method = "POST"; 
request.ContentType = "application/json"; 
request.ContentLength = data.Length; 

using (var stream = request.GetRequestStream()) 
{ 
stream.Write(data, 0, data.Length); 
} 

var response = (HttpWebResponse)request.GetResponse(); 

var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();