BloggingSystem.Services.Controllers.UsersController.RegisterUser C# (CSharp) Method

        public HttpResponseMessage RegisterUser([FromBody]UserRegisterModel user)
        {
            HttpResponseMessage responseMessage = this.PerformOperation(() =>
            {
                UserValidator.ValidateAuthenticationCode(user.AuthCode);
                UserValidator.ValidateDisplayName(user.DisplayName);
                UserValidator.ValidateUsername(user.Username);

                var context = new BloggingSystemContext();
                using (context)
                {
                    User exstingUserEntity = context.Users.FirstOrDefault<User>(
                        u => u.Username == user.Username.ToLower() || u.DisplayName.ToLower() == user.DisplayName.ToLower());
                    if (exstingUserEntity != null)
                    {
                        throw new InvalidOperationException("User already exists!");
                    }

                    User newUserEntity = UsersMapper.ToEntity(user);
                    context.Users.Add(newUserEntity);
                    context.SaveChanges();

                    newUserEntity.SessionKey = UserValidator.GenerateSessionKey(newUserEntity.ID);
                    context.SaveChanges();

                    UserLoggedModel loggedUser = UsersMapper.ToModel(newUserEntity);
                    return this.Request.CreateResponse(HttpStatusCode.Created, loggedUser);
                }
            });

            return responseMessage;
        }