WAF SynchronizingList improve two-way synchronization by not re-creat…

…ing a model upon Insert or SetItem
jbe2277 · Oct 2, 2023 · 2ce9311 · 2ce9311
1 parent eb317a2
commit 2ce9311
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Showing 2 changed files with 36 additions and 10 deletions.
diff --git a/src/System.Waf/System.Waf/System.Waf.Core.Test/Foundation/SynchronizingListTest.cs b/src/System.Waf/System.Waf/System.Waf.Core.Test/Foundation/SynchronizingListTest.cs
@@ -121,7 +121,9 @@ public void SynchronizeWithGetOriginalItemTest()
             };
             AssertCollectionChangeEventsCalled(handler, () => originalList.Add(new MyModel()));
             originalList.Remove(originalList.Last());
-            AssertCollectionChangeEventsCalled(handler, () => synchronizingList.Add(new MyDataModel(new MyModel())));
+            var dataModelToAdd = new MyDataModel(new MyModel());
+            AssertCollectionChangeEventsCalled(handler, () => synchronizingList.Add(dataModelToAdd));
+            Assert.AreSame(dataModelToAdd, synchronizingList.Last());
 
             // Check insert at index 0 operation with collection changed event.
             handler = (sender, e) =>
@@ -132,7 +134,21 @@ public void SynchronizeWithGetOriginalItemTest()
             };
             AssertCollectionChangeEventsCalled(handler, () => originalList.Insert(0, new MyModel()));
             originalList.RemoveAt(0);
-            AssertCollectionChangeEventsCalled(handler, () => synchronizingList.Insert(0, new MyDataModel(new MyModel())));
+            var dataModelToInsert = new MyDataModel(new MyModel());
+            AssertCollectionChangeEventsCalled(handler, () => synchronizingList.Insert(0, dataModelToInsert));
+            Assert.AreSame(dataModelToInsert, synchronizingList[0]);
+
+            // Check replace operation with collection changed event.
+            handler = (sender, e) =>
+            {
+                Assert.AreEqual(NotifyCollectionChangedAction.Replace, e.Action);
+                Assert.AreEqual(0, e.NewStartingIndex);
+                Assert.AreEqual(originalList[0], e.NewItems!.Cast<MyDataModel>().Single().Model);
+            };
+            AssertCollectionChangeEventsCalled(handler, () => originalList[0] = new MyModel());
+            var dataModelToReplace = new MyDataModel(new MyModel());
+            AssertCollectionChangeEventsCalled(handler, () => synchronizingList[0] = dataModelToReplace);
+            Assert.AreSame(dataModelToReplace, synchronizingList[0]);
 
             // Compare the collections
             AssertHelper.SequenceEqual(originalList, synchronizingList.Select(dm => dm.Model));

diff --git a/src/System.Waf/System.Waf/System.Waf.Core/Foundation/SynchronizingList.cs b/src/System.Waf/System.Waf/System.Waf.Core/Foundation/SynchronizingList.cs
@@ -23,6 +23,7 @@ public class SynchronizingList<T, TOriginal> : ObservableList<T>
         private readonly Func<T, TOriginal>? getOriginalItem;
         private readonly bool isReadOnly;
         private bool innerChange;
+        private bool outerChange;
 
         /// <summary>Initializes a new instance of the <see cref="SynchronizingList{T, TOriginal}"/> class with two-way synchronization support.</summary>
         /// <param name="originalList">The original list.</param>
@@ -61,6 +62,7 @@ private SynchronizingList(ObservableCollection<TOriginal>? originalList, IEnumer
         private void OriginalCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
             if (e == null) throw new ArgumentNullException(nameof(e));
+            if (outerChange) return;
             innerChange = true;
             try
             {
@@ -116,24 +118,32 @@ private void OriginalCollectionChanged(object? sender, NotifyCollectionChangedEv
                     foreach (TOriginal x in originalCollection) Add(CreateItem(x));
                 }
             }
-            finally
-            {
-                innerChange = false;
-            }
+            finally { innerChange = false; }
         }
 
         /// <inheritdoc />
         protected override void InsertItem(int index, T item)
         {
-            if (innerChange) base.InsertItem(index, item);
-            else ModifyOriginalList().Insert(index, GetOriginalItem(item));
+            if (!innerChange)
+            {
+                outerChange = true;
+                try { ModifyOriginalList().Insert(index, GetOriginalItem(item)); }
+                finally { outerChange = false; }
+            }
+            base.InsertItem(index, item);
+
         }
 
         /// <inheritdoc />
         protected override void SetItem(int index, T item)
         {
-            if (innerChange) base.SetItem(index, item);
-            else ModifyOriginalList()[index] = GetOriginalItem(item);
+            if (!innerChange)
+            {
+                outerChange = true;
+                try { ModifyOriginalList()[index] = GetOriginalItem(item); }
+                finally { outerChange = false; }
+            }
+            base.SetItem(index, item);
         }
 
         /// <inheritdoc />