使用 C# 调用 json

In your code you don't get the HttpResponse, so you won't see what the server side sends you back.

你需要得到类似于你得到请求的方式的回复.所以

public static bool SendAnSMSMessage(string message)
{
  var httpWebRequest = (HttpWebRequest)WebRequest.Create("http://api.pennysms.com/jsonrpc");
  httpWebRequest.ContentType = "text/json";
  httpWebRequest.Method = "POST";

  using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
  {
    string json = "{ \"method\": \"send\", " +
                      "  \"params\": [ " +
                      "             \"IPutAGuidHere\", " +
                      "             \"msg@MyCompany.com\", " +
                      "             \"MyTenDigitNumberWasHere\", " +
                      "             \"" + message + "\" " +
                      "             ] " +
                      "}";

    streamWriter.Write(json);
  }
  var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
  using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
  {
    var responseText = streamReader.ReadToEnd();
    //Now you have your response.
    //or false depending on information in the response
    return true;        
  }
}

I also notice in the pennysms documentation that they expect a content type of "text/json" and not "application/json". That may not make a difference, but it's worth trying in case it doesn't work.