c# .net 3.5 post json httpclient
System.Net.WebClient client = new System.Net.WebClient();
client.Headers.Add("content-type", "application/json");//set your header here, you can add multiple headers
string s = Encoding.ASCII.GetString(client.UploadData("http://localhost:1111/Service.svc/SignIn", "POST", Encoding.Default.GetBytes("{\"EmailId\": \"[email protected]\",\"Password\": \"pass#123\"}")));