From f9663a9e80936ad4e8f56bafecead071074dbc2b Mon Sep 17 00:00:00 2001
From: Stephan <sgay@pilotine.com>
Date: Wed, 2 Oct 2013 13:59:02 +0200
Subject: [PATCH] Core.EnumerableExtensions - refactor InGroupsOf to enumerate
 source only once

---
 src/Umbraco.Core/EnumerableExtensions.cs | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/Umbraco.Core/EnumerableExtensions.cs b/src/Umbraco.Core/EnumerableExtensions.cs
index 3fa4847a26..dfdd26cd84 100644
--- a/src/Umbraco.Core/EnumerableExtensions.cs
+++ b/src/Umbraco.Core/EnumerableExtensions.cs
@@ -13,14 +13,23 @@ namespace Umbraco.Core
     {
         public static IEnumerable<IEnumerable<T>> InGroupsOf<T>(this IEnumerable<T> source, int groupSize)
         {
-            var i = 0;
-            var length = source.Count();
+            if (source == null)
+               throw new NullReferenceException("source");
 
-            while ((i * groupSize) < length)
+            // enumerate the source only once!
+            var enumerator = source.GetEnumerator();
+
+            while (enumerator.MoveNext())
+                yield return EnumerateGroup(enumerator, groupSize);
+        }
+
+        private static IEnumerable<T> EnumerateGroup<T>(IEnumerator<T> enumerator, int count)
+        {
+            var c = 1;
+            do
             {
-                yield return source.Skip(i * groupSize).Take(groupSize);
-                i++;
-            }
+                yield return enumerator.Current;
+            } while (c++ < count && enumerator.MoveNext());
         }