C#Linq To Entry

public void updateUser(Server.Data.User User, out string resMsg)
        {           
            try
            {               
                var tempF = db.User.First(f => f.Id == User.Id);
                var tempFT = db.UserType.First(ft => ft.Id == User.UserTypeId);
                if (tempF!=null)
                {
                    if (tempFT != null)
                    {
                        tempF.CreatorId = User.CreatorId;
                        tempF.UserName = User.UserName;
                        tempF.UserSize = User.UserSize;
                        tempF.UserType = tempFT;
                        tempF.LatestVersion = User.LatestVersion;
                        tempF.ModifierId = User.ModifierId;
                        tempF.ModifyDate = DateTime.Now.ToString();
                        db.SaveChanges();
                        resMsg = "Update User success";
                    }
                    else
                    {
                        resMsg = "Update User failure：UserType not found";
                    }
                }
                else
                {
                    resMsg = "Update User failure：User not found";
                }
            }
            catch (Exception ex)
            {
                resMsg = "Update User failure\n" + ex.ToString();
            }
        }注意外鍵約束，如果主鍵ID為自增長，注意將表的 IDentity 設為 on