Securing and authenticating azure service bus relay messages using a shared secret. : http://acaseyblog.wordpress.com/2013/03/22/securing-and-authenticating-azure-service-bus-relay-messages-using-a-shared-secret/

gistfile1.cs

 using (var serviceRequest = new WebClient())
      {
      string token = GetAuthorizationToken("yourservice","owner", "NW1wr7/nlgggTFnB5L7nDBrOLC+o1E1P4ZZqPaP2mY4=");
      serviceRequest.Headers["Authorization"] = string.Format("WRAP access_token=\"{0}\"", token);
      string response = serviceRequest.DownloadString(new Uri(url));
      return response;
    }


// connects to ACS and gets WRAP Authorization token

public string GetAuthorizationToken(string serviceNamespace, string issuerName, string issuerPassword)
        {
            string acsEndpoint = "https://" + serviceNamespace + "-sb.accesscontrol.windows.net/WRAPv0.9";
            string relyingPartyAddress = "http://" + serviceNamespace + ".servicebus.windows.net";

            NameValueCollection postData = new NameValueCollection
            {
                { "wrap_scope", relyingPartyAddress },
                { "wrap_name", issuerName },
                { "wrap_password", issuerPassword },
            };

            WebClient webClient = new WebClient();
            byte[] responseBuffer = webClient.UploadValues(acsEndpoint, "POST", postData);
            string response = Encoding.UTF8.GetString(responseBuffer);

            string encodedtoken = response.Split('&')
                .Single(value => value.StartsWith("wrap_access_token="))
                .Split('=')[1];

            string token = System.Web.HttpUtility.UrlDecode(encodedtoken);
            
            return token;
        }