c# - LINQ LEFT JOIN，用 OR 组合多个 WHERE 子句

Question

林奇，

var clause = PredicateBuilder.False<User>();
clause = clause.Or(u => u.uid.Equals(1));
clause = clause.Or(u => u.uid.Equals(2));

var usersInGroup = (from u in db.Users
                    join g in db.GroupUsers
                        on u.uid equals g.uid
                        into ug
                    from g in ug.DefaultIfEmpty()
                    where g.gid.Equals(0)
                    select u).Where(clause);

这两个 where 子句链接在一起；

WHERE ([t0].[gid] = 0) AND (([t1].[uid] = 1) 或 ([t1].[uid] = 2))

如何添加两个where条件

WHERE ([t0].[gid] = 0) 或 (([t1].[uid] = 1) 或 ([t1].[uid] = 2))

Answer 1

感谢，

Can PredicateBuilder generate predicates that span multiple tables?

我现在有了一个可行的解决方案，但我的结果集是基于一个新的混合类。结果，我不得不反射(reflect)所有相关领域。见下文。

public class HybridGroupUser {
    private User _user;
    public User User {
        get { return _user; }
        set {
            _user = value;
            if (value != null) {
                uid = value.uid;
                fname = value.fname;
                lname = value.lname;
                email = value.email;
            }
        }
    }
    private GroupUser _GroupUser;
    public GroupUser GroupUser {
        get { return _GroupUser; }
        set {
            _GroupUser = value;
            if (value != null) {
                uid = value.uid;
                fname = value.fname;
                lname = value.lname;
                email = value.email;
            }
        }
    }

    public int? uid { get; set; }
    public string fname { get; set; }
    public string lname { get; set; }
    public string email { get; set; }
}

有了这个类(class)，我现在可以做以下事情；

var clause = PredicateBuilder.False<HybridGroupUser>();

clause = clause.Or(u => u.GroupUser.gid.Equals(0);
foreach (int i in AddedUsers) {
    int tmp = i;
    clause = clause.Or(u => u.User.uid.Equals(tmp));
}

var usersInGroup = (from u in db.Users
                    join gusr in db.GroupUser
                        on u.uid equals gusr.uid
                        into ug
                    from gusr in ug.DefaultIfEmpty()
                    select new HybridGroupUser {
                       User = u, 
                       GroupUser = gusr
                    }).Where(clause);