Redmine REST upload file

Redmine redmine = new Redmine();
RestClient client = new RestClient("http://localhost/redmine/");
client.Authenticator = new HttpBasicAuthenticator("myuser", "mypsw");
var request2 = new RestRequest("uploads.json", Method.POST);
request2.AddHeader("Content-Type", "application/octet-stream");
request2.RequestFormat = RestSharp.DataFormat.Json;
byte[] dataToSend = File.ReadAllBytes(AddIssue.attach.Text);
request2.AddBody(dataToSend);
IRestResponse response2 = client.Execute(request2);
resultbox.Text = response2.Content;