C# 如何使用linq对嵌套数据进行排序

我有这样一个分类表：

id parentid Title     
1  0        Parent1   
2  1        Child1        
3  0        Parent2
4  3        Child2
5  1        anotherChild1
6  3        anotherChild2

如何按以下顺序对其进行排序：

Parent1
  child1
  anotherchild1
Parent2
  child2
  anotherchild2

---

并将顺序保存到另一个名为排序索引的字段中？

这适用于任何层次结构

public void CustomSort()
{
    List<MyNode> nodes = new List<MyNode>();
    nodes.Add(new MyNode() { Id = 5, ParentId = 1, Title = "Anotherchild1" });
    nodes.Add(new MyNode() { Id = 6, ParentId = 3, Title = "Anotherchild2" });
    nodes.Add(new MyNode() { Id = 7, ParentId = 6, Title = "Anotherchild3" });
    nodes.Add(new MyNode() { Id = 1, ParentId = 0, Title = "Parent1" });
    nodes.Add(new MyNode() { Id = 2, ParentId = 1, Title = "Child1" });
    nodes.Add(new MyNode() { Id = 3, ParentId = 0, Title = "Parent2" });
    nodes.Add(new MyNode() { Id = 4, ParentId = 3, Title = "Child2" });

    Func<MyNode, List<int>> hierarchy = null;
    hierarchy = n =>
    {
        var n2 = nodes.FirstOrDefault(x => x.Id == n.ParentId);
        if (n2 != null) return hierarchy(n2).Concat(new List<int>() { n.Id }).ToList();
        return new List<int>() { n.ParentId,n.Id };
    };

    var debug = nodes.Select(x=>hierarchy(x)).ToList();

    var sortedList = nodes.OrderBy(n => String.Join(",", hierarchy(n).Select(x=>x.ToString("X8"))))
                          .ToList();
}

class MyNode
{
    public int Id;
    public int ParentId;
    public string Title;
}

---

如果您的继承权只有两个级别，那么您可以将父母与子女合并，展平结果列表，然后包含每个人的索引

var parents = people.Where(p => p.ParentId < 1).ToList();
var children = people.Where(p => p.ParentId >= 1).ToList();

var ordered = (from parent in parents
               join child in children on parent.Id equals child.ParentId into childGroup
               from person in (new [] { parent }).Concat(childGroup)
               select person)
              .Select((person, sortedIndex) => new { person, sortedIndex });

---

嗨，L.B，非常感谢你的回答，我很忙，你能解释一下你是如何得到层次结构的吗？为什么要转换成stringx8？@Kiddo 1 hierarcy是一个递归函数。它使用节点返回hierarchyn2的parentid调用自己，并在展开时收集节点的id。解释递归函数比编写更难：。2我从列表中形成一个字符串。例如，0 1 2转换为0000000 10002。原因是您无法将列表与a==b进行比较，因为它们是引用类型。另一种选择是编写定制的iComparer，这可能更好，但这会增加答案的大小，让每个人都感到害怕。

var parents = people.Where(p => p.ParentId < 1).ToList();
var children = people.Where(p => p.ParentId >= 1).ToList();

var ordered = (from parent in parents
               join child in children on parent.Id equals child.ParentId into childGroup
               from person in (new [] { parent }).Concat(childGroup)
               select person)
              .Select((person, sortedIndex) => new { person, sortedIndex });