通过递归检查父子关系的C＃编译树类型列表 [英] Build tree type list by recursively checking parent-child relationship C#

问题描述

我有一个具有其自身的列表，以便它可以重新$ P $以树结构psented一类

I have One class that has a list of itself so it can be represented in a tree structure.

我拉着这些类的平面列表，并希望unflatten它。

I am pulling a flat list of these classes and want to unflatten it.

public class Group
{
     public int ID {get;set;}

     public int? ParentID {get;set;}

     public List<Group> Children {get;set;}

}

我希望能够做到以下几点

I want to be able to do the following

List<Group> flatList = GetFlatList() //I CAN ALREADY DO THIS
List<Group> tree = BuildTree(flatList);

相关ID属性其父组PARENTID如果wasnt明显。

The ParentID related to the ID property on its parent group if that wasnt obvious.

修改

有一些混乱，为什么我返回一个列表，而不是一个单一的对象。

There is some confusion as to why I am returning a list and not a single object.

我的建筑，项目列表的UI元素，每为什么有一个孩子。因此，最初的名单没有一个根节点。似乎所有的解决方案，至今没有工作。

I am building a UI element that has a list of items, each of why has a child. So the initial list DOES NOT have a root node. It seems all of the solutions so far do not work.

这意味着我需要基本使用组分类型结构的列表。

What this means is I essentially need a list of tree type structures using Group class.

推荐答案

我不知道为什么你希望你的 BuildTree 方法返回列表＆LT;组＆gt ; - 树需要有根节点，所以你应该希望它返回一个组元素，而不是一个列表

I have no idea why you want your BuildTree method return List<Group> - tree needs to have root node, so you should expect it to return single Group element, not a list.

我要创建的扩展方法IEnumerable＆LT;组＆gt; ：

public static class GroupEnumerable
{
    public static IList<Group> BuildTree(this IEnumerable<Group> source)
    {
        var groups = source.GroupBy(i => i.ParentID);

        var roots = groups.FirstOrDefault(g => g.Key.HasValue == false).ToList();

        if (roots.Count > 0)
        {
            var dict = groups.Where(g => g.Key.HasValue).ToDictionary(g => g.Key.Value, g => g.ToList());
            for (int i = 0; i < roots.Count; i++)
                AddChildren(roots[i], dict);
        }

        return roots;
    }

    private static void AddChildren(Group node, IDictionary<int, List<Group>> source)
    {
        if (source.ContainsKey(node.ID))
        {
            node.Children = source[node.ID];
            for (int i = 0; i < node.Children.Count; i++)
                AddChildren(node.Children[i], source);
        }
        else
        {
            node.Children = new List<Group>();
        }
    }
}

用法的

Usage

var flatList = new List<Group>() {
    new Group() { ID = 1, ParentID = null },    // root node
    new Group() { ID = 2, ParentID = 1 },
    new Group() { ID = 3, ParentID = 1 },
    new Group() { ID = 4, ParentID = 3 },
    new Group() { ID = 5, ParentID = 4 },
    new Group() { ID = 6, ParentID = 4 }
};


var tree = flatList.BuildTree();

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