EntityFramework Inner Exception Catch

在保存时加入这一段，就可以查看error具体是哪里出错了。正式发布需要删除这段，try catch毕竟会影响性能

 try
                {
                    entity.SaveChanges();
                }
                catch (DbEntityValidationException e)
                {
                    string error = "";
                    foreach (var eve in e.EntityValidationErrors)
                    {
                        error += string.Format("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:",
                             eve.Entry.Entity.GetType().Name, eve.Entry.State);
                        foreach (var ve in eve.ValidationErrors)
                        {
                            error += string.Format("- Property: \"{0}\", Error: \"{1}\"",
                                ve.PropertyName, ve.ErrorMessage);
                        }
                    }
                    throw new Exception(error);
                }