Retail_manager/RMDataManager/Controllers/UserController.cs

using RMDataManagerLibrary.DataAcccess;
using System.Collections.Generic;
using System.Web.Http;
using RMDataManagerLibrary.Models;
using System.Web;
using Microsoft.AspNet.Identity;
using System.Linq;

namespace RMDataManager.Controllers
{
    [Authorize]
    public class UserController : ApiController
    {
        [HttpGet]
        public UserModel GetById()
        {
            string userId = RequestContext.Principal.Identity.GetUserId();

            UserData data = new UserData();

            return data.GetUserById(userId).First();
        }   
    }
}