public void Update (Rate a)
{
a = (from ee in DataContext.Rates
where ee.users_Id == a.users_Id && ee.books_Id == a.books_Id
select ee).SingleOrDefault();
DataContext.SubmitChanges();
}
错误:
违反PRIMARY KEY约束'PK_Rates' . 无法在对象'dbo.Rates'中插入重复键 . 重复键值为(3,1) .