--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Chronosv2/source/Extensions/LinqExtensions.cs	Tue Feb 21 17:25:44 2012 +0700
@@ -0,0 +1,62 @@
+/*
+The MIT License
+
+Copyright (c) 2009-2010. Carlos Guzmán Álvarez. http://chronoswpf.codeplex.com/
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+*/
+
+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+
+namespace Chronos.Extensions
+{
+    public static class LinqExtensions
+    {
+        #region · Extensions ·
+
+        /// <summary>
+        /// Traverses the specified source.
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="source">The source.</param>
+        /// <param name="fnRecurse">The fn recurse.</param>
+        /// <returns></returns>
+        public static IEnumerable<T> Traverse<T>(this IEnumerable<T> source, Func<T, IEnumerable<T>> fnRecurse)
+        {
+            foreach (T item in source)
+            {
+                yield return item;
+
+                IEnumerable<T> seqRecurse = fnRecurse(item);
+
+                if (seqRecurse != null)
+                {
+                    foreach (T itemRecurse in Traverse(seqRecurse, fnRecurse))
+                    {
+                        yield return itemRecurse;
+                    }
+                }
+            }
+        }
+
+        #endregion
+    }
+}