使用Linq从嵌套集合模型树中获取子树

public class TreeNode
{
    public int Id { get; set; }
    public string Name { get; set; }
    public List<TreeNode> Children { get; set; }
}

public static class TreeExtensions
{
    public static IEnumerable<TreeNode> GetSubtree(this TreeNode node, int targetId)
    {
        if (node.Id == targetId)
        {
            yield return node;
        }

        foreach (var child in node.Children)
        {
            foreach (var subtreeNode in child.GetSubtree(targetId))
            {
                yield return subtreeNode;
            }
        }
    }
}

public static void Main(string[] args)
{
    // 构造一个嵌套集合模型树
    var root = new TreeNode
    {
        Id = 1,
        Name = "Root",
        Children = new List<TreeNode>
        {
            new TreeNode
            {
                Id = 2,
                Name = "Child 1",
                Children = new List<TreeNode>
                {
                    new TreeNode
                    {
                        Id = 3,
                        Name = "Grandchild 1",
                        Children = new List<TreeNode>()
                    },
                    new TreeNode
                    {
                        Id = 4,
                        Name = "Grandchild 2",
                        Children = new List<TreeNode>()
                    }
                }
            },
            new TreeNode
            {
                Id = 5,
                Name = "Child 2",
                Children = new List<TreeNode>()
            }
        }
    };

    // 使用Linq查询语句从嵌套集合模型树中获取子树
    int targetId = 2;
    var subtree = root.GetSubtree(targetId);

    // 输出子树的节点信息
    foreach (var node in subtree)
    {
        Console.WriteLine($"Id: {node.Id}, Name: {node.Name}");
    }
}