使用Linq读取层次结构中的最后一个子项
本文关键字:最后一个 Linq 读取 层次结构 使用 | 更新日期: 2023-09-27 18:25:59
我有一个表,它包含下面的层次结构
ParentChildMap
{
parent_id,
child_id
}
另一个表包含Map 中每个成员的详细信息
Member_Details
{
Member_Id,
Member_Name
}
有时关系可以简单到Parent---->Child,有时关系可以有多个级别,如GG祖父-->G-GrandFather--->GrandFather-->Parent---->Child。
我想做的是列出某个家庭的所有孩子及其详细信息。
有人能帮我提供最有效的LINQ查询吗?
我意识到这个问题已经4年多没有答案了,但它似乎是一个有趣的问题。我认为以下方法应该适用于Linq查询。我基本上是在假设孩子不是父母。因此,如果这是真的,那么一个保留join的关系本身应该会产生所有不是父节点的节点。完成此操作后,详细信息的常规联接将与子节点的名称相匹配。以下是我的示例代码:
void Main()
{
// 1
// 2 3
// 4
// 5 6
// Child nodes are all those that are not parents: i.e.: 5, 6, 3
var details = new[] {
new Member_Details { Member_Id = 1, Member_Name = "Node 1" },
new Member_Details { Member_Id = 2, Member_Name = "Node 2" },
new Member_Details { Member_Id = 3, Member_Name = "Node 3" },
new Member_Details { Member_Id = 4, Member_Name = "Node 4" },
new Member_Details { Member_Id = 5, Member_Name = "Node 5" },
new Member_Details { Member_Id = 6, Member_Name = "Node 6" },
};
var relationships = new[] {
new ParentChildMap { parent_id = 1, child_id = 2 },
new ParentChildMap { parent_id = 1, child_id = 3 },
new ParentChildMap { parent_id = 2, child_id = 4 },
new ParentChildMap { parent_id = 4, child_id = 5 },
new ParentChildMap { parent_id = 4, child_id = 6 }
};
var children = relationships
.GroupJoin(relationships, r1 => r1.child_id, r2 => r2.parent_id, (r1, r2) => r2
.Select(x => new { Inner = r1.child_id, Outer = x.child_id})
.DefaultIfEmpty(new { Inner = r1.child_id, Outer = 0 }))
.SelectMany(x => x)
.Where(x => x.Outer == 0)
.Join(details, r => r.Inner, d => d.Member_Id, (r, d) => new {Id = r.Inner, Name = d.Member_Name});
foreach (var child in children)
{
Console.WriteLine($"ID: {child.Id}, Name: {child.Name}");
}
}
public class ParentChildMap
{
public int parent_id;
public int child_id;
}
public class Member_Details
{
public int Member_Id;
public string Member_Name;
}