/Controllers/AuthenticationController.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Configuration;
using System.Web.Http;
using Newtonsoft.Json.Linq;

namespace HCHunchApp.Web.Controllers
{
    public class AuthenticationController : ApiController
    {
        private class AuthResponse
        {
            public string status { get; set; }
            public string ok { get; set; }
            public string auth_token { get; set; }
            public string user_id { get; set; }
        }

        // GET api/authentication
        public IEnumerable<string> Get()
        {
            return new string[] { "value1", "value2" };
        }

        // GET api/authentication/5
        public string Get(string id)
        {
            var auth_sig = WebConfigurationManager.AppSettings["auth_sig"];
            var app_id = WebConfigurationManager.AppSettings["app_id"];
            var getAuthTokenUrl = WebConfigurationManager.AppSettings["get_auth_token_url"];
            var url = String.Format(getAuthTokenUrl, app_id, id, auth_sig);

            var authTokenRequest = (HttpWebRequest)WebRequest.Create(url);
            authTokenRequest.ContentType = "application/json; charset=utf-8";

            var authTokenResponse = (HttpWebResponse)authTokenRequest.GetResponse();

            var responseData = new JObject();
            using (var sr = new StreamReader(authTokenResponse.GetResponseStream()))
            {
                var data = sr.ReadToEnd();
                responseData = JObject.Parse(data);
            }

            var auth_token = (string)responseData["auth_token"];

            return auth_token;
        }

        // POST api/authentication
        public void Post([FromBody]string value)
        {
        }

        // PUT api/authentication/5
        public void Put(int id, [FromBody]string value)
        {
        }

        // DELETE api/authentication/5
        public void Delete(int id)
        {
        }
    }
}