Make BindingList adaptors replace the changed item instead of re-adding (#694)

Author: Metadorius

src/DynamicData/Binding/BindingListAdaptor.cs

@@ -119,23 +119,18 @@ private static void DoUpdate(IChangeSet<TObject, TKey> changes, BindingList<TObj
                         break;
 
                     case ChangeReason.Update:
-                        var item = update.Previous.Value;
-
-                        if (item is not null)
-                        {
-                            list.Remove(item);
-                        }
-
-                        list.Add(update.Current);
+                        var previousIndex = list.IndexOf(update.Previous.Value);
+                        if (previousIndex >= 0)
+                            list[previousIndex] = update.Current;
+                        else
+                            list.Add(update.Current);
                         break;
 
                     case ChangeReason.Refresh:
-                        {
-                            var index = list.IndexOf(update.Current);
-                            if (index != -1)
-                                list.ResetItem(index);
-                            break;
-                        }
+                        var index = list.IndexOf(update.Current);
+                        if (index != -1)
+                            list.ResetItem(index);
+                        break;
                 }
             }
         }

src/DynamicData/Binding/SortedBindingListAdaptor.cs

@@ -100,17 +100,27 @@ private void DoUpdate(ISortedChangeSet<TObject, TKey> changes)
                         break;
 
                     case ChangeReason.Update:
-                        _list.RemoveAt(change.PreviousIndex);
-                        _list.Insert(change.CurrentIndex, change.Current);
+                        if (change.CurrentIndex != change.PreviousIndex)
+                        {
+                            _list.RemoveAt(change.PreviousIndex);
+                            _list.Insert(change.CurrentIndex, change.Current);
+                        }
+                        else
+                        {
+                            var previousIndex = _list.IndexOf(change.Previous.Value);
+                            if (previousIndex >= 0)
+                                _list[previousIndex] = change.Current;
+                            else
+                                _list.Add(change.Current);
+                        }
+
                         break;
 
                     case ChangeReason.Refresh:
-                        {
-                            var index = _list.IndexOf(change.Current);
-                            if (index != -1)
-                                _list.ResetItem(index);
-                            break;
-                        }
+                        var index = _list.IndexOf(change.Current);
+                        if (index != -1)
+                            _list.ResetItem(index);
+                        break;
                 }
             }
         }