API Calls : JSON Request

public static string GetHeader(string username, string password)
{
    var httpWebRequest = (HttpWebRequest)WebRequest.Create("https://api.google.com/header");
    httpWebRequest.ContentType = "application/json";
    httpWebRequest.Method = "POST";

    using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
    {
        string json = "{\"usercode\":\""+username+"\"," +
                        "\"password\":\""+password+"\"}";

        streamWriter.Write(json);
    }

    var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
    using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
    {
        var result = streamReader.ReadToEnd();

        return result;
    }
}