Ancestors and Descendants for Tree handling

treehelper.cs

using System;
using System.Collections.Generic;

public static class Extensions
{
    static public IEnumerable<T> Descendants<T>(this IEnumerable<T> source, Func<T, IEnumerable<T>> descendBy)
    {
        foreach (T value in source)
        {
            yield return value;

            foreach (T child in descendBy(value).Descendants<T>(descendBy))
            {
                yield return child;
            }
        }
    }

    static public IEnumerable<T> Ancestors<T>(this T source, Func<T, T> parentOf)
    {
        var Parent = parentOf(source);
        while (Parent != null)
        {
            yield return Parent;
            Parent = parentOf(Parent);
        }
    }
}