Question

我有3个班级：

public class HoteAvail
{
    public int HotelID { get; set; }
    public string Name { get; set; }
    public List<Room> Rooms { get; set; }

}

public class Room
{
    public int RoomID { get; set; }
    public string RoomName { get; set; }
}

public class DAL
{

    public static List<HoteAvail> GetAll()
    {
        return new List<HoteAvail>()
        {

           new  HoteAvail{HotelID=1,Name="Taj",Rooms=new List<Room>(){new Room{RoomID=1,RoomName="Deliux"}}},
           new  HoteAvail{HotelID=2,Name="x",Rooms=new List<Room>(){new Room{RoomID=2,RoomName="dd"},new Room{RoomID=1,RoomName="qq"}}},
           new  HoteAvail{HotelID=3,Name="y",Rooms=new List<Room>(){new Room{RoomID=3,RoomName="yy"},new Room{RoomID=1,RoomName="rr"}}},

        };
    }

    public static List<HoteAvail> GetAllII()
    {
        return new List<HoteAvail>()
        {

           new  HoteAvail{HotelID=1,Name="Taj",Rooms=new List<Room>(){new Room{RoomID=1,RoomName="Deliux"},new Room{RoomID=1,RoomName="pp"}}},
           new  HoteAvail{HotelID=4,Name="x",Rooms=new List<Room>(){new Room{RoomID=2,RoomName="dd"},new Room{RoomID=1,RoomName="qq"}}},
           new  HoteAvail{HotelID=5,Name="y",Rooms=new List<Room>(){new Room{RoomID=3,RoomName="yy"},new Room{RoomID=1,RoomName="rr"}}},

        };
    }
}

我想加入DAL.GetAll（）和DAL.GetAllII（）的值，结果应该只包含那些酒店ID不匹配的值。

最终结果集应该是：

new HoteAvail{HotelID=2,Name="x",Rooms=new List<Room>(){new Room{RoomID=2,RoomName="dd"},new Room{RoomID=1,RoomName="qq"}}},
new HoteAvail{HotelID=3,Name="y",Rooms=new List<Room>(){new Room{RoomID=3,RoomName="yy"},new Room{RoomID=1,RoomName="rr"}}},
new HoteAvail{HotelID=4,Name="x",Rooms=new List<Room>(){new Room{RoomID=2,RoomName="dd"},new Room{RoomID=1,RoomName="qq"}}},
new  HoteAvail{HotelID=5,Name="y",Rooms=new List<Room>(){new Room{RoomID=3,RoomName="yy"},new Room{RoomID=1,RoomName="rr"}}}

我试过了：

var groupBNames = new HashSet<string>(DAL.GetAll().Select(x => x.HotelID.ToString()));
var filteredEmployees = DAL.GetAllII().Where(x => !groupBNames.Contains(x.HotelID.ToString()));

var resultList = from a in DAL.GetAll()
where !(DAL.GetAllII().Any(HotelID => HotelID == a))
    select a;

但我没有取得任何成功。提前谢谢。

Answer 1

我建议使用自定义IEqualityComparer做2个例外。您可以使用this method创建比较器：

// create a comparer to compare HotelAvail objects by hotelId
// see http://www.codeducky.org/10-utilities-c-developers-should-know-part-two/
// for the implementation of EqualityComparers.Create, which is a nice shortcut
var comparer = EqualityComparers.Create<HoteAvail>(ha => ha.HotelId); // compare by hotelId

var results = 
    // first take all entries in GetAll() NOT IN GetAllII()
    DAL.GetAll().Except(DAL.GetAllII(), comparer)
        // then add all entries in GetAllII() NOT IN GetAll()
        .Concat(DAL.GetAllII()).Except(DAL.GetAll(), comparer);

Answer 2

您可以实施自定义IEqualityComparer<HoteAvail>：

public class HoteAvailComparer: IEqualityComparer<HoteAvail>
{
    public bool Equals(HoteAvail x, HoteAvail y)
    {
        return x != null && y != null && x.HotelID == y.HotelID;
    }

    public int GetHashCode(HoteAvail obj)
    {
        return obj.HotelID;
    }
}

你可以使用Enumerable.Except这是有效的，因为它使用了一个集合：

var resultList = DAL.GetAll().Except(DAL.GetAllII(), new HoteAvailComparer());
Console.WriteLine(String.Join(",", resultList.Select(h => h.HotelID))); // 2,3

<强>更新

它给了我HotelId 2,3，我想加入它的价值观 DAL.GetAll（）和DAL.GetAllII（）和结果应该只包含那些酒店ID不匹配的值。结果应该有 HotelId 2,3,4,5

然后你需要从两个角度使用Except：

var hotelComparer = new HoteAvailComparer();
var all1 = DAL.GetAll();
var all2 = DAL.GetAllII();
var resultList = all1.Except(all2, hotelComparer).Concat(all2.Except(all1, hotelComparer));

期望的结果2,3,4,5：

Console.WriteLine(String.Join(",", resultList.Select(h => h.HotelID)));

当然，您也可以使用Concat和GroupBy，但效率和可维护性较低：

resultList = all1.Concat(all2).GroupBy(h => h.HotelID)
    .Where(g => g.Count() == 1)
    .SelectMany(g => g);

您可以将IEqualityComparer<HoteAvail>用于许多其他LINQ方法，例如GroupBy + Distinct，Join，Intersect等。

Linq加入不平等

2 个答案: