c# - 将两个具有不同对象的列表相交

Question

我有一个 ObjA 和 ObjB 列表，如下所示:

List<ObjA> List1;
List<ObjB> List2;

ObjA 和 ObjB 都有一个公共(public)字段，即用户，我想根据 User.Id 将它们相交。

class ObjA
{ 
  User user;
  .... other properties
}

class ObjB
{ 
  User user;
  .... other properties
}

class User
{
    int Id;
     .... other props
}

如何将 User.Id 上的这两个列表与 linq 相交？

结果，我只想要用户列表。

Answer 1

1.看这个简单的代码

  var result = (from objA in objAList
                join objB in objBList on objA.user.Id equals objB.user.Id
                select objA/*or objB*/).ToList();

2.完整的代码

 class QueryJoin
{
    static void Main(string[] args)
    {
        //create users
        User user1 = new User { Id = 1, Name = "anuo1" };
        User user2 = new User { Id = 2, Name = "anuo2" };
        User user3 = new User { Id = 3, Name = "anuo3" };
        User user4 = new User { Id = 4, Name = "anuo4" };
        User user5 = new User { Id = 5, Name = "anuo5" };
        //create objAList
        List<ObjA> objAList = new List<ObjA>();
        objAList.Add(new ObjA { user = user1 });
        objAList.Add(new ObjA { user = user2 });
        objAList.Add(new ObjA { user = user3 });
        //create objBList
        List<ObjB> objBList = new List<ObjB>();
        objBList.Add(new ObjB { user = user3 });
        objBList.Add(new ObjB { user = user4 });
        objBList.Add(new ObjB { user = user5 });

        //intersect
        var result = (from objA in objAList
                      join objB in objBList on objA.user.Id equals objB.user.Id
                      select objA/*or objB*/).ToList();

    }

}

class ObjA
{
    public User user { get; set; }
}

class ObjB
{
    public User user { get; set; }
}

class User
{
    public int Id { get; set; }
    public string Name { get; set; }
}