From bf4b07b2acdbe6edb73e8d884004294260ea4109 Mon Sep 17 00:00:00 2001
From: Andrew Hoefling <andrew@hoeflingsoftware.com>
Date: Sun, 10 Mar 2019 22:25:55 -0400
Subject: [PATCH] Added new OnCollectionChanged overloads to reduce need for
 additional if checks.

---
 .../ObjectModel/ObservableCollection.cs       | 36 ++++++++++---------
 .../ObservableCollection_MethodsTest.cs       |  2 +-
 2 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs b/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs
index 0ea90f49e780..ea7768af7282 100644
--- a/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs
+++ b/src/System.ObjectModel/src/System/Collections/ObjectModel/ObservableCollection.cs
@@ -218,7 +218,7 @@ protected override void ReplaceItemsRange(int index, int count, IEnumerable<T> c
             
             OnCountPropertyChanged();
             OnIndexerPropertyChanged();
-            OnCollectionChanged(NotifyCollectionChangedAction.Replace, itemsToReplace, collection, index);
+            OnCollectionChanged(NotifyCollectionChangedAction.Replace, itemsToReplace, (IList)collection, index);
         }
 
 
@@ -397,14 +397,15 @@ protected void CheckReentrancy()
         /// </summary>
         private void OnCollectionChanged(NotifyCollectionChangedAction action, object item, int index)
         {
-            if (item is IList)
-            {
-                OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, (IList)item, index));
-            }
-            else
-            {
-                OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, item, index));
-            }
+            OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, item, index));
+        }
+
+        /// <summary>
+        /// Helper to raise CollectionChanged event to any listeners
+        /// </summary>
+        private void OnCollectionChanged(NotifyCollectionChangedAction action, IList items, int index)
+        {
+            OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, items, index));
         }
 
         /// <summary>
@@ -420,14 +421,15 @@ private void OnCollectionChanged(NotifyCollectionChangedAction action, object it
         /// </summary>
         private void OnCollectionChanged(NotifyCollectionChangedAction action, object oldItem, object newItem, int index)
         {
-            if (oldItem is IList && newItem is IList)
-            {
-                OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, (IList)oldItem, (IList)newItem, index));
-            }
-            else
-            {
-                OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, newItem, oldItem, index));
-            }
+            OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, newItem, oldItem, index));
+        }
+
+        /// <summary>
+        /// Helper to raise CollectionChanged event to any listeners
+        /// </summary>
+        private void OnCollectionChanged(NotifyCollectionChangedAction action, IList oldItems, IList newItems, int index)
+        {
+            OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, newItems, oldItems, index));
         }
 
         /// <summary>
diff --git a/src/System.ObjectModel/tests/ObservableCollection/ObservableCollection_MethodsTest.cs b/src/System.ObjectModel/tests/ObservableCollection/ObservableCollection_MethodsTest.cs
index 6f0a180315ac..504f899fa070 100644
--- a/src/System.ObjectModel/tests/ObservableCollection/ObservableCollection_MethodsTest.cs
+++ b/src/System.ObjectModel/tests/ObservableCollection/ObservableCollection_MethodsTest.cs
@@ -690,7 +690,7 @@ public static void RemoveRange_NotifyCollectionChanged_EventArgs_IndexOfZero_Tes
         }
 
         [Fact]
-        public static void RemoveRange_NotifyCollectionChanged_EventArgs_IndexMiddle_Test()
+        public static void RemoveRange_NotifyCollectionChanged_EventArgs_IndexMiddle_Test() 
         {
             int[] initialData = new int[] { 1, 2, 3, 4, 5, 6, 7, 8 };
             int[] actualDataRemoved = new int[0];