EF 4.0 Linq to Enity 查询

Question

大家好，我需要在 Linq to Entity 中复制此 SQL 查询，

  select * from Subscriber a
  inner join User b on a.UserId = b.Id

  where b.Username = 'Name'

可能有人会有所帮助。

Answer 1

试试这个：

var query = from s in context.Subscribers.Include("User")
            where s.User.Username == "Name"
            select s;

假设 Subscriber 具有引用用户实例的导航属性 User。

如果您想使用联接（不需要），您可以将其用于内联接：

var query = from s in context.Subscribers
            join u in context.Users on s.User.Id equals u.Id
            where u.Username == "Name"
            select new 
                {
                    Subscriber = s, 
                    User = u
                };

或将其用于左外联接：

var query = from s in context.Subscribers
            join u in context.Users on s.User.Id equals u.Id into x
            where u.Username == "Name"
            from y in x.DefaultIfEmpty()
            select new 
                {
                    Subscriber = s 
                    User = y,
                };