[c#] POSTing JSON to URL via WebClient in C#

You need a json serializer to parse your content, probably you already have it, for your initial question on how to make a request, this might be an idea:

var baseAddress = "http://www.example.com/1.0/service/action";

var http = (HttpWebRequest)WebRequest.Create(new Uri(baseAddress));
http.Accept = "application/json";
http.ContentType = "application/json";
http.Method = "POST";

string parsedContent = <<PUT HERE YOUR JSON PARSED CONTENT>>;
ASCIIEncoding encoding = new ASCIIEncoding();
Byte[] bytes = encoding.GetBytes(parsedContent);

Stream newStream = http.GetRequestStream();
newStream.Write(bytes, 0, bytes.Length);
newStream.Close();

var response = http.GetResponse();

var stream = response.GetResponseStream();
var sr = new StreamReader(stream);
var content = sr.ReadToEnd();

hope it helps,