From 91cf0139693372cf488eaec2c978973af885b2bb Mon Sep 17 00:00:00 2001
From: Andrew Hoefling <andrew@hoeflingsoftware.com>
Date: Sun, 10 Mar 2019 22:07:56 -0400
Subject: [PATCH] Updated removedItems to use an array instead of a List<T>

---
 .../ObjectModel/ObservableCollection.cs       | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs b/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs
index 032ae1a697ad..0ea90f49e780 100644
--- a/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs
+++ b/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs
@@ -146,10 +146,17 @@ protected override void RemoveItemsRange(int index, int count)
                 length = index + count;
             }
 
-            List<T> removedItems = new List<T>();
-            for (int i = index; i < length; i++)
+            T[] oldItems = new T[Items.Count];
+            if (Items is List<T> list)
             {
-                removedItems.Add(this[i]);
+                list.CopyTo(oldItems);
+            }
+            else
+            {
+                for (int i = 0; i < oldItems.Length; i++)
+                {
+                    oldItems[i] = this[i];
+                }
             }
 
             bool ignore = _skipRaisingEvents;
@@ -172,6 +179,12 @@ protected override void RemoveItemsRange(int index, int count)
             
             if (count > 0 && !_skipRaisingEvents)
             {
+                T[] removedItems = new T[count];
+                for (int i = 0; i < count; i++)
+                {
+                    removedItems[i] = oldItems[index + i];
+                }
+
                 OnCountPropertyChanged();
                 OnIndexerPropertyChanged();
                 OnCollectionChanged(NotifyCollectionChangedAction.Remove, removedItems, index);