如何使用LINQ选择复合对象的所有后代

public class Node
{
    public int Id { get; set; }
    public List<Node> Children { get; set; }
}

public static IEnumerable<Node> GetAllDescendants(Node node)
{
    yield return node;

    if (node.Children != null)
    {
        foreach (var child in node.Children)
        {
            foreach (var descendant in GetAllDescendants(child))
            {
                yield return descendant;
            }
        }
    }
}

public static void Main()
{
    // 创建一个示例对象树
    var root = new Node
    {
        Id = 1,
        Children = new List<Node>
        {
            new Node
            {
                Id = 2,
                Children = new List<Node>
                {
                    new Node { Id = 3 },
                    new Node { Id = 4 }
                }
            },
            new Node { Id = 5 },
            new Node { Id = 6 }
        }
    };

    // 使用LINQ选择复合对象的所有后代
    var descendants = GetAllDescendants(root);

    foreach (var descendant in descendants)
    {
        Console.WriteLine(descendant.Id);
    }
}