--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MetroWpf/MetroWpf.Framework/Extensions/LinqExtensions.cs	Mon Mar 12 23:05:21 2012 +0800
@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+
+namespace MetroWpf
+{
+    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
+    }
+}