我正在尝试将包含备用家族对的DTOs列表进行分组，以以下格式将它们分组，以最大程度地减少重复。
这是我目前拥有的DTO结构，您可以看到它们具有重复的行，这些行也可以基于反向关系分组在一起。
+----------+------------+-----------+
| PersonId | RelativeId | Relation |
+----------+------------+-----------+
| 1 | 2 | "Son" |
| 2 | 1 | "Father" |
| 1 | 3 | "Mother" |
| 3 | 1 | "Son" |
| 2 | 3 | "Husband" |
| 3 | 2 | "Wife" |
+----------+------------+-----------+
变成这样：
+----------+------------+-----------+-----------------+
| PersonId | RelativeId | Relation | ReverseRelation |
+----------+------------+-----------+-----------------+
| 1 | 2 | "Son" | "Father" |
| 1 | 3 | "Mother" | "Son" |
| 2 | 3 | "Husband" | "Wife" |
+----------+------------+-----------+-----------------+
我正在尝试的代码：
Program.cs
class Program
{
static void Main(string[] args)
{
List<RelationDTO> relationDTOList = new List<RelationDTO>
{
new RelationDTO { PersonId = 1, RelativeId = 2, Relation = "Son" },
new RelationDTO { PersonId = 2, RelativeId = 1, Relation = "Father" },
new RelationDTO { PersonId = 1, RelativeId = 3, Relation = "Mother" },
new RelationDTO { PersonId = 3, RelativeId = 1, Relation = "Son" },
new RelationDTO { PersonId = 2, RelativeId = 3, Relation = "Husband" },
new RelationDTO { PersonId = 3, RelativeId = 2, Relation = "Wife" },
};
var grp = relationDTOList.GroupBy(x => new { x.PersonId }).ToList();
}
}
RelationDTO.cs
public class RelationDTO
{
public int PersonId { get; set; }
public int RelativeId { get; set; }
public string Relation { get; set; }
}
Relations.cs
public class Relations
{
public int PersonId { get; set; }
public int RelativeId { get; set; }
public string Relation { get; set; }
public string ReverseRelation { get; set; }
}
答案 0 :(得分：8)
您可以使用联接操作，例如
var result = relationDTOList
.Where(v => v.PersonId < v.RelativeId)
.Join(
relationDTOList.Where(v => v.PersonId > v.RelativeId),
v => new Key{PersonId = v.PersonId, RelativeId = v.RelativeId},
v => new Key{PersonId = v.RelativeId, RelativeId = v.PersonId},
(p, q) => new Relations
{
PersonId = p.PersonId,
RelativeId = p.RelativeId,
Relation = p.Relation,
ReverseRelation = q.Relation
}
);
Key是：
public struct Key
{
public int PersonId { get; set; }
public int RelativeId { get; set; }
}
答案 1 :(得分：7)
我不确定这是否是您所需要的：
public static void Main()
{
List<RelationDTO> relationDTOList = new List<RelationDTO>
{
new RelationDTO { PersonId = 1, RelativeId = 2, Relation = "Son" },
new RelationDTO { PersonId = 2, RelativeId = 1, Relation = "Father" },
new RelationDTO { PersonId = 1, RelativeId = 3, Relation = "Mother" },
new RelationDTO { PersonId = 3, RelativeId = 1, Relation = "Son" },
new RelationDTO { PersonId = 2, RelativeId = 3, Relation = "Husband" },
new RelationDTO { PersonId = 3, RelativeId = 2, Relation = "Wife" },
};
var grp = relationDTOList.Join(relationDTOList,
dto => dto.PersonId + "-" + dto.RelativeId,
dto => dto.RelativeId + "-" + dto.PersonId,
(dto1, dto2) => new Relations
{
PersonId = dto1.PersonId,
RelationId = dto1.RelativeId,
Relation = dto1.Relation,
ReverseRelation = dto2.Relation
}).Distinct(new MyEqualityComparer());
foreach (var g in grp)
Console.WriteLine("{0},{1},{2},{3}", g.PersonId, g.RelationId, g.Relation, g.ReverseRelation);
}
public class MyEqualityComparer : IEqualityComparer<Relations>
{
public bool Equals(Relations x, Relations y)
{
return x.PersonId + "-" + x.RelationId == y.PersonId + "-" + y.RelationId ||
x.PersonId + "-" + x.RelationId == y.RelationId + "-" + y.PersonId;
}
public int GetHashCode(Relations obj)
{
return 0;
}
}
答案 2 :(得分：6)
我有点怀疑LINQ是这里的最佳选择，因为使用查找循环可能会更有效率。但是，如果您确实需要LINQ，则可以执行以下操作
var relations = from person in relationDTOList
// Match on the exact pair of IDs
join relative in relationDTOList on
new { person.PersonId, person.RelativeId } equals
new { PersonId = relative.RelativeId, RelativeId = relative.PersonId }
// Build the new structure
let relation = new Relations {
PersonId = person.PersonId,
Relation = person.Relation,
RelativeId = relative.PersonId,
ReverseRelation = relative.Relation
}
// Order the pairs to find the duplicates
let ids = new[] {person.PersonId, relative.PersonId}.OrderBy(x => x).ToArray()
group relation by new { FirstPersonId = ids[0], SecondPersonId = ids[1] }
into relationGroups
// Select only the the first of two duplicates
select relationGroups.First();
此代码的作用是将集合自身与匹配对PersonId，RelativeId相连，然后过滤掉每对的第二条记录，从而得到一个集合，其中第一个人在列表将被视为该关系中的 parent 。
编辑：我正在谈论的查找方法：
var result = new List<Relations>();
while (relationDTOList.Any())
{
var person = relationDTOList.First();
relationDTOList.RemoveAt(0);
var relative = relationDTOList.Where(x =>
x.PersonId == person.RelativeId && x.RelativeId == person.PersonId)
.Select((x, i) => new {Person = x, Index = i}).FirstOrDefault();
if (relative != null)
{
relationDTOList.RemoveAt(relative.Index);
result.Add(new Relations {
PersonId = person.PersonId,
Relation = person.Relation,
RelativeId = relative.Person.PersonId,
ReverseRelation = relative.Person.Relation
});
}
}
请注意，它会清空您的原始列表，因此，如果您在代码中进一步需要它，则必须进行复制（list.ToList()）。
运行该代码的速度大约是我之前发布的join的方法的六倍。我还想出了以下分组方法，该分组方法比 join 的运行速度快得多，尽管它做的非常相似，但它仍然比 lookup-and-remove 方法慢。
var relations = relationDTOList.GroupBy(person =>
person.PersonId < person.RelativeId
? new {FirstPersonId = person.PersonId, SecondPersonId = person.RelativeId}
: new {FirstPersonId = person.RelativeId, SecondPersonId = person.PersonId})
.Select(group => new Relations {
PersonId = group.First().PersonId,
Relation = group.First().Relation,
RelativeId = group.First().RelativeId,
ReverseRelation = group.Last().Relation
});
答案 3 :(得分：4)
var query = relationDTOList.OrderBy(x=>x.PersonId).GroupJoin(relationDTOList,
p => p.PersonId,
a => a.RelativeId,
(p, al) =>
new
{
p.PersonId,
p.RelativeId,
p.Relation,
Parrent = al.Where(x => x.PersonId == p.RelativeId && x.RelativeId == p.PersonId).SingleOrDefault().Relation
}
).ToList();
答案 4 :(得分：3)
您可以将Groupby与Tuple和PersonId的{{1}}进行排序，然后选择第一项作为第一关系，第二项选择为反向关系。
演示：
RelativeId输出：
using System;
using System.Collections.Generic;
using System.Linq;
namespace Example {
public static class Program {
public static void Main (string[] args) {
List<RelationDTO> relationDTOList = new List<RelationDTO> {
new RelationDTO { PersonId = 1, RelativeId = 2, Relation = "Son" },
new RelationDTO { PersonId = 2, RelativeId = 1, Relation = "Father" },
new RelationDTO { PersonId = 1, RelativeId = 3, Relation = "Mother" },
new RelationDTO { PersonId = 3, RelativeId = 1, Relation = "Son" },
new RelationDTO { PersonId = 2, RelativeId = 3, Relation = "Husband" },
new RelationDTO { PersonId = 3, RelativeId = 2, Relation = "Wife" },
};
// Group relations into list of lists
var groups = relationDTOList
.GroupBy (r => GetOrderedTuple (r.PersonId, r.RelativeId))
.Select (grp => grp.ToList ()).ToList ();
// Output original relations and their reverse relations
foreach (var group in groups) {
var relation = group.ElementAt (0);
var reverseRelation = group.ElementAt (1);
FormattableString relationOutput = $"PersonId={relation.PersonId} RelativeId={relation.RelativeId} Relation={relation.Relation} ReverseRelation={reverseRelation.Relation}";
Console.WriteLine (relationOutput);
}
}
private static Tuple<int, int> GetOrderedTuple (int n1, int n2) {
if (n1 < n2) {
return Tuple.Create (n1, n2);
}
return Tuple.Create (n2, n1);
}
}
}
答案 5 :(得分：1)
这可以做到。但是它需要原始列表中的副本。
var result = relationDTOList
.Where(v => v.PersonId < v.RelativeId)
.GroupJoin(relationDTOList,
p => p.PersonId,
a => a.RelativeId,
(p, al) =>
new{
p.PersonId,
p.RelativeId,
p.Relation,
ReverseRelation = al.Where( x =>
x.PersonId == p.RelativeId &&
x.RelativeId == p.PersonId )
.SingleOrDefault()
.Relation} ).ToList();