递归过滤Linq到对象

public static class RecursiveLinqExtensions
{
    public static IEnumerable<T> Traverse<T>(this T source, Func<T, IEnumerable<T>> childrenSelector)
    {
        yield return source;
        foreach (var child in childrenSelector(source) ?? Enumerable.Empty<T>())
        foreach (var descendant in child.Traverse(childrenSelector))
            yield return descendant;
    }

    public static IEnumerable<T> Traverse<T>(this IEnumerable<T> source, Func<T, IEnumerable<T>> childrenSelector)
    {
        foreach (var item in source)
        foreach (var descendant in item.Traverse(childrenSelector))
            yield return descendant;
    }
}

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

public static void Main(string[] args)
{
    var root = new Node
    {
        Value = 1,
        Children = new List<Node>
        {
            new Node
            {
                Value = 2,
                Children = new List<Node>
                {
                    new Node {Value = 4},
                    new Node {Value = 5}
                }
            },
            new Node
            {
                Value = 3,
                Children = new List<Node>
                {
                    new Node {Value = 6},
                    new Node {Value = 7}
                }
            }
        }
    };

    var result = root.Traverse(n => n.Children).Where(n => n.Value > 3).ToList();
}