尝试提取EntityValidationErrors时尝试/捕获失败

Question

我的程序出现问题，无法保存到数据库。我收到＆＃34;一个或多个实体的验证失败。请参阅＆＃39; EntityValidationErrors＆＃39;物业详情。＆＃34;我上网后发现了一些关于应用Try / Catch＆＃34; SaveChanges（）＆＃34;的文章。这个项目是MVC。该项目在本地工作没有问题，但当我按下它时，我收到错误消息。

控制器

//
    // GET: /Account/LogOff

    [Authorize]
    public ActionResult LogOff()
    {
            // get user information
            var user = Membership.GetUser();
            var userId = (int)user.ProviderUserKey;
            var userProfile = db.UserProfiles.Where(up => up.UserId == userId).Single();

            // used to display notifications, last login date is set when the user logs off
            var profile = db.UserProfiles.Where(up => up.UserId == userId).Single();
            profile.LastLoginDate = DateTime.Now.AddHours(2);
            db.Entry(profile).State = EntityState.Modified;

            try
            {
                // doing my logic here
                db.SaveChanges();
            }
            catch (DbEntityValidationException dbEx)
            {
                foreach (var validationErrors in dbEx.EntityValidationErrors)
                {
                    foreach (var validationError in validationErrors.ValidationErrors)
                    {
                        Trace.TraceInformation("Property: {0} Error: {1}", validationError.
          PropertyName, validationError.ErrorMessage);
                    }
                }

            }

            FormsAuthentication.SignOut();
            return RedirectToAction("LogOn", "Account"); // return user to login screen
    }