1:  /// <summary>

   2:  ///     Recursively projects each nested element to an <see cref="IEnumerable{TSource}"/>

   3:  ///     and flattens the resulting sequences into one sequence.

   4:  /// </summary>

   5:  /// <typeparam name="TSource">The type of the elements of <paramref name="source"/>.</typeparam>

   6:  /// <param name="source">A sequence of values to project.</param>

   7:  /// <param name="recursiveSelector">A transform to apply to each element.</param>

   8:  /// <returns>

   9:  ///     An <see cref="IEnumerable{TSource}"/> whose elements are the

  10:  ///     result of recursively invoking the recursive transform function

  11:  ///     on each element and nested element of the input sequence.

  12:  /// </returns>

  13:  public static IEnumerable<TSource> SelectRecursive<TSource>(

  14:      this IEnumerable<TSource> source, Func<TSource, IEnumerable<TSource>> recursiveSelector)

  15:  {

  16:      Util.RequireNotNull(source, "start");

  17:      Util.RequireNotNull(recursiveSelector, "children");

  18:   

  19:      Stack<TSource> stack = new Stack<TSource>();

  20:   

  21:      source.Reverse().ForEach(stack.Push);

  22:   

  23:      while (stack.Count > 0)

  24:      {

  25:          TSource current = stack.Pop();

  26:   

  27:          recursiveSelector(current).Reverse().ForEach(stack.Push);

  28:   

  29:          yield return current;

  30:   

  31:      } // while

  32:   

  33:  } //*** SelectRecursive

  34:   

  35:  /// <summary>

  36:  ///     Performs the specified <paramref name="action"/> to 

  37:  ///     on each element of the specified <paramref name="source"/>.

  38:  /// </summary>

  39:  /// <typeparam name="TSource">The type of the elements of <paramref name="source"/>.</typeparam>

  40:  /// <param name="source">The sequence to which is applied the specified <paramref name="action"/>.</param>

  41:  /// <param name="action">The action applied to each element in <paramref name="source"/>.</param>

  42:  public static void ForEach<TSource>(this IEnumerable<TSource> source, Action<TSource> action)

  43:  {

  44:      Util.RequireNotNull(source, "source");

  45:      Util.RequireNotNull(action, "action");

  46:   

  47:      foreach (TSource item in source)

  48:      {

  49:          action(item);

  50:      }

  51:  }