Upload photo to Tumblr using RestSharp

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C#

I'm tying to upload photo to Tumblr via RestSharp. Here are my code.

var restClient = new RestClient("http://tumblr.com/api/write");
  var request = new RestRequest(Method.POST);


  request.RequestFormat = DataFormat.Json;

  request.AddParameter("email", "123@456.com");
  request.AddParameter("password", "acb");
  request.AddParameter("type", "photo");
  request.AddParameter("caption", "testing");
  request.AddFile("data", "C:\\photo\\photo1.jpg");

  IRestResponse response = restClient.Execute(request);

Nothing happen after the code been executed. Is there anything wrong with my code? Thanks in advance.

p.s : Is oauth needed?