public async Task <IHttpActionResult> Register(RegisterBindingModel model) { if (!ModelState.IsValid) { return(BadRequest(ModelState)); } Data.posDBDataContext db = new Data.posDBDataContext(); var currentUser = from d in db.MstUsers where d.UserName.Equals(model.UserName) select d; if (!currentUser.Any()) { return(BadRequest("Username does not exist.")); } var user = new ApplicationUser() { UserName = currentUser.FirstOrDefault().UserName, Email = currentUser.FirstOrDefault().UserName }; IdentityResult result = await UserManager.CreateAsync(user, currentUser.FirstOrDefault().Password); if (!result.Succeeded) { return(GetErrorResult(result)); } string registeredAspUserId = user.Id; if (currentUser.Any()) { var updateCurrentUser = currentUser.FirstOrDefault(); updateCurrentUser.AspNetUserId = registeredAspUserId; db.SubmitChanges(); } return(Ok()); }