diff --git a/sandbox/WpfApp/MainWindow.xaml b/sandbox/WpfApp/MainWindow.xaml
index e9d7411..fbe633b 100644
--- a/sandbox/WpfApp/MainWindow.xaml
+++ b/sandbox/WpfApp/MainWindow.xaml
@@ -5,29 +5,62 @@
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
         xmlns:local="clr-namespace:WpfApp"
         mc:Ignorable="d"
-        Title="MainWindow" Height="450" Width="800">
-    <!--<Grid>
+        Title="MainWindow" Height="800" Width="800">
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="*" />
+            <RowDefinition Height="*" />
+        </Grid.RowDefinitions>
         <Grid.ColumnDefinitions>
-            <ColumnDefinition />
-            <ColumnDefinition />
+            <ColumnDefinition Width="*" />
+            <ColumnDefinition Width="*" />
         </Grid.ColumnDefinitions>
 
-        <ListView ItemsSource="{Binding ItemsView}"></ListView>
-        
-        <Button Grid.Column="1" Click="Button_Click">Insert</Button>
+        <!-- original -->
+        <StackPanel Grid.Row="0" Grid.ColumnSpan="2" Orientation="Vertical">
+            <ListBox ItemsSource="{Binding ItemsView}" />
+            <Button Content="Add" Command="{Binding AddCommand}" />
+            <Button Content="AddRange" Command="{Binding AddRangeCommand}" />
+            <Button Content="Insert" Command="{Binding InsertAtRandomCommand}" />
+            <Button Content="Remove" Command="{Binding RemoveAtRandomCommand}" />
+            <Button Content="RemoveRange" Command="{Binding RemoveRangeCommand}" />
+            <Button Content="Clear" Command="{Binding ClearCommand}" />
+            <Button Content="Reverse" Command="{Binding ReverseCommand}" />
+            <Button Content="Sort" Command="{Binding SortCommand}" />
+        </StackPanel>
 
-    </Grid>-->
-    <StackPanel>
-        <ListBox ItemsSource="{Binding ItemsView}" />
-        <Button Content="Add" Command="{Binding AddCommand}" />
-        <Button Content="AddRange" Command="{Binding AddRangeCommand}" />
-        <Button Content="Insert" Command="{Binding InsertAtRandomCommand}" />
-        <Button Content="Remove" Command="{Binding RemoveAtRandomCommand}" />
-        <Button Content="RemoveRange" Command="{Binding RemoveRangeCommand}" />
-        <Button Content="Clear" Command="{Binding ClearCommand}" />
-        <Button Content="Reverse" Command="{Binding ReverseCommand}" />
-        <Button Content="Sort" Command="{Binding SortCommand}" />
-        <Button Content="AttachFilter" Command="{Binding AttachFilterCommand}" />
-        <Button Content="ResetFilter" Command="{Binding ResetFilterCommand}" />
-    </StackPanel>
-</Window>
+        <!-- Upper left (NotWritable, NonFilter) -->
+        <GroupBox Grid.Row="1" Grid.Column="0" Header="NotWritable, NonFilter">
+            <StackPanel Orientation="Vertical">
+                <DataGrid ItemsSource="{Binding NotWritableNonFilterView}" />
+            </StackPanel>
+        </GroupBox>
+
+        <!-- Upper right (Writable, NonFilter) -->
+        <GroupBox Grid.Row="1" Grid.Column="1" Header="Writable, NonFilter">
+            <StackPanel Orientation="Vertical">
+                <DataGrid ItemsSource="{Binding WritableNonFilterPersonView}" />
+            </StackPanel>
+        </GroupBox>
+
+        <!-- Lower left (NotWritable, Filter) -->
+        <GroupBox Grid.Row="2" Grid.Column="0" Header="NotWritable, Filter">
+            <StackPanel Orientation="Vertical">
+                <DataGrid ItemsSource="{Binding NotWritableFilterView}" />
+                <Button Content="AttachFilter" Command="{Binding AttachFilterCommand2}" />
+                <Button Content="ResetFilter" Command="{Binding ResetFilterCommand2}" />
+            </StackPanel>
+        </GroupBox>
+
+        <!-- Lower right (Writable, Filter) -->
+        <GroupBox Grid.Row="2" Grid.Column="1" Header="Writable, Filter">
+            <StackPanel Orientation="Vertical">
+                <DataGrid ItemsSource="{Binding WritableFilterPersonView}" />
+                <Button Content="AttachFilter" Command="{Binding AttachFilterCommand3}" />
+                <Button Content="ResetFilter" Command="{Binding ResetFilterCommand3}" />
+            </StackPanel>
+        </GroupBox>
+
+    </Grid>
+</Window>
\ No newline at end of file
diff --git a/sandbox/WpfApp/MainWindow.xaml.cs b/sandbox/WpfApp/MainWindow.xaml.cs
index 8c476e2..519cdd4 100644
--- a/sandbox/WpfApp/MainWindow.xaml.cs
+++ b/sandbox/WpfApp/MainWindow.xaml.cs
@@ -87,6 +87,18 @@ namespace WpfApp
         public ReactiveCommand<Unit> AttachFilterCommand { get; } = new ReactiveCommand<Unit>();
         public ReactiveCommand<Unit> ResetFilterCommand { get; } = new ReactiveCommand<Unit>();
 
+        private ObservableList<Person> SourceList { get; } = [];
+        private IWritableSynchronizedView<Person, Person> writableFilter;
+        private ISynchronizedView<Person, Person> notWritableFilter;
+        public NotifyCollectionChangedSynchronizedViewList<Person> NotWritableNonFilterView { get; }
+        public NotifyCollectionChangedSynchronizedViewList<Person> NotWritableFilterView { get; }
+        public NotifyCollectionChangedSynchronizedViewList<Person> WritableNonFilterPersonView { get; }
+        public NotifyCollectionChangedSynchronizedViewList<Person> WritableFilterPersonView { get; }
+        public ReactiveCommand<Unit> AttachFilterCommand2 { get; } = new ReactiveCommand<Unit>();
+        public ReactiveCommand<Unit> ResetFilterCommand2 { get; } = new ReactiveCommand<Unit>();
+        public ReactiveCommand<Unit> AttachFilterCommand3 { get; } = new ReactiveCommand<Unit>();
+        public ReactiveCommand<Unit> ResetFilterCommand3 { get; } = new ReactiveCommand<Unit>();
+
         public ViewModel()
         {
             observableList.Add(1);
@@ -156,8 +168,97 @@ namespace WpfApp
             {
                 view.ResetFilter();
             });
+
+            SourceList.Add(new() { Name = "a", Age = 1 });
+            SourceList.Add(new() { Name = "b", Age = 2 });
+            SourceList.Add(new() { Name = "c", Age = 3 });
+            SourceList.Add(new() { Name = "d", Age = 4 });
+            //NotWritable, NonFilter
+            NotWritableNonFilterView = SourceList.ToNotifyCollectionChanged();
+
+            //NotWritable, Filter
+            notWritableFilter = SourceList.CreateView(x => x);
+            NotWritableFilterView = notWritableFilter.ToNotifyCollectionChanged();
+
+            //Writable, NonFilter
+            WritableNonFilterPersonView = SourceList.ToWritableNotifyCollectionChanged();
+
+            //WritableNonFilterPersonView = SourceList.ToWritableNotifyCollectionChanged(x => x, (Person newView, Person original, ref bool setValue) =>
+            //{
+            //    if (setValue)
+            //    {
+            //        // default setValue == true is Set operation
+            //        original.Name = newView.Name;
+            //        original.Age = newView.Age;
+
+            //        // You can modify setValue to false, it does not set original collection to new value.
+            //        // For mutable reference types, when there is only a single,
+            //        // bound View and to avoid recreating the View, setting false is effective.
+            //        // Otherwise, keeping it true will set the value in the original collection as well,
+            //        // and change notifications will be sent to lower-level Views(the delegate for View generation will also be called anew).
+            //        setValue = false;
+            //        return original;
+            //    }
+            //    else
+            //    {
+            //        // default setValue == false is Add operation
+            //        return new Person { Age = newView.Age, Name = newView.Name };
+            //    }
+            //}, null);
+
+            //Writable, Filter
+            writableFilter = SourceList.CreateWritableView(x => x);
+            WritableFilterPersonView = writableFilter.ToWritableNotifyCollectionChanged();
+
+            //WritableFilterPersonView = writableFilter.ToWritableNotifyCollectionChanged((Person newView, Person original, ref bool setValue) =>
+            //{
+            //    if (setValue)
+            //    {
+            //        // default setValue == true is Set operation
+            //        original.Name = newView.Name;
+            //        original.Age = newView.Age;
+
+            //        // You can modify setValue to false, it does not set original collection to new value.
+            //        // For mutable reference types, when there is only a single,
+            //        // bound View and to avoid recreating the View, setting false is effective.
+            //        // Otherwise, keeping it true will set the value in the original collection as well,
+            //        // and change notifications will be sent to lower-level Views(the delegate for View generation will also be called anew).
+            //        setValue = false;
+            //        return original;
+            //    }
+            //    else
+            //    {
+            //        // default setValue == false is Add operation
+            //        return new Person { Age = newView.Age, Name = newView.Name };
+            //    }
+            //});
+
+            AttachFilterCommand2.Subscribe(_ =>
+            {
+                notWritableFilter.AttachFilter(x => x.Age % 2 == 0);
+            });
+
+            ResetFilterCommand2.Subscribe(_ =>
+            {
+                notWritableFilter.ResetFilter();
+            });
+
+            AttachFilterCommand3.Subscribe(_ =>
+            {
+                writableFilter.AttachFilter(x => x.Age % 2 == 0);
+            });
+
+            ResetFilterCommand3.Subscribe(_ =>
+            {
+                writableFilter.ResetFilter();
+            });
         }
     }
+    public class Person
+    {
+        public int? Age { get; set; }
+        public string? Name { get; set; }
+    }
 
     public class WpfDispatcherCollection(Dispatcher dispatcher) : ICollectionEventDispatcher
     {
diff --git a/src/ObservableCollections/IObservableCollection.cs b/src/ObservableCollections/IObservableCollection.cs
index 9134cbf..8dd232a 100644
--- a/src/ObservableCollections/IObservableCollection.cs
+++ b/src/ObservableCollections/IObservableCollection.cs
@@ -57,7 +57,12 @@ namespace ObservableCollections
         void SetViewAt(int index, TView view);
         void SetToSourceCollection(int index, T value);
         void AddToSourceCollection(T value);
+        void InsertIntoSourceCollection(int index, T value);
+        bool RemoveFromSourceCollection(T value);
+        void RemoveAtSourceCollection(int index);
+        void ClearSourceCollection();
         IWritableSynchronizedViewList<TView> ToWritableViewList(WritableViewChangedEventHandler<T, TView> converter);
+        NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged();
         NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged(WritableViewChangedEventHandler<T, TView> converter);
         NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged(ICollectionEventDispatcher? collectionEventDispatcher);
         NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged(WritableViewChangedEventHandler<T, TView> converter, ICollectionEventDispatcher? collectionEventDispatcher);
@@ -99,8 +104,8 @@ namespace ObservableCollections
         }
 
         public abstract int Count { get; }
-        public bool IsReadOnly => false;
-        public bool IsFixedSize => false;
+        public virtual bool IsReadOnly { get; } = true;
+        public bool IsFixedSize => IsReadOnly;
         public bool IsSynchronized => true;
         public object SyncRoot => gate;
 
@@ -112,9 +117,14 @@ namespace ObservableCollections
         int IList.Add(object? value)
         {
             Add((TView)value!);
-            return -1; // itself does not add in this collection
+            return Count - 1;
         }
 
+        public abstract void Insert(int index, TView item);
+        public abstract bool Remove(TView item);
+        public abstract void RemoveAt(int index);
+        public abstract void Clear();
+
         public abstract bool Contains(TView item);
 
         bool IList.Contains(object? value)
@@ -149,17 +159,43 @@ namespace ObservableCollections
             return value is TView || value == null && default(TView) == null;
         }
 
-        void ICollection<TView>.Clear() => throw new NotSupportedException();
-        void IList.Clear() => throw new NotSupportedException();
+        void ICollection<TView>.Clear()
+        {
+            Clear();
+        }
+        void IList.Clear()
+        {
+            Clear();
+        }
 
         void ICollection<TView>.CopyTo(TView[] array, int arrayIndex) => throw new NotSupportedException();
         void ICollection.CopyTo(Array array, int index) => throw new NotSupportedException();
 
-        void IList<TView>.Insert(int index, TView item) => throw new NotSupportedException();
-        void IList.Insert(int index, object? value) => throw new NotSupportedException();
-        bool ICollection<TView>.Remove(TView item) => throw new NotSupportedException();
-        void IList.Remove(object? value) => throw new NotSupportedException();
-        void IList.RemoveAt(int index) => throw new NotSupportedException();
+        void IList<TView>.Insert(int index, TView item)
+        {
+            Insert(index, item);
+        }
+
+        void IList.Insert(int index, object? value)
+        {
+            Insert(index, (TView)value!);
+        }
+
+        bool ICollection<TView>.Remove(TView item)
+        {
+            return Remove(item!);
+        }
+
+        void IList.Remove(object? value)
+        {
+            Remove((TView)value!);
+        }
+
+        void IList.RemoveAt(int index)
+        {
+            RemoveAt(index);
+        }
+
         void IList<TView>.RemoveAt(int index) => throw new NotSupportedException();
     }
 
@@ -176,25 +212,25 @@ namespace ObservableCollections
             return new NonFilteredSynchronizedViewList<T, TView>(collection.CreateView(transform), isSupportRangeFeature: true, null, null);
         }
 
-        public static INotifyCollectionChangedSynchronizedViewList<T> ToNotifyCollectionChanged<T>(this IObservableCollection<T> collection)
+        public static NotifyCollectionChangedSynchronizedViewList<T> ToNotifyCollectionChanged<T>(this IObservableCollection<T> collection)
         {
             return ToNotifyCollectionChanged(collection, null);
         }
 
-        public static INotifyCollectionChangedSynchronizedViewList<T> ToNotifyCollectionChanged<T>(this IObservableCollection<T> collection, ICollectionEventDispatcher? collectionEventDispatcher)
+        public static NotifyCollectionChangedSynchronizedViewList<T> ToNotifyCollectionChanged<T>(this IObservableCollection<T> collection, ICollectionEventDispatcher? collectionEventDispatcher)
         {
             return ToNotifyCollectionChanged(collection, static x => x, collectionEventDispatcher);
         }
 
-        public static INotifyCollectionChangedSynchronizedViewList<TView> ToNotifyCollectionChanged<T, TView>(this IObservableCollection<T> collection, Func<T, TView> transform)
+        public static NotifyCollectionChangedSynchronizedViewList<TView> ToNotifyCollectionChanged<T, TView>(this IObservableCollection<T> collection, Func<T, TView> transform)
         {
             return ToNotifyCollectionChanged(collection, transform, null!);
         }
 
-        public static INotifyCollectionChangedSynchronizedViewList<TView> ToNotifyCollectionChanged<T, TView>(this IObservableCollection<T> collection, Func<T, TView> transform, ICollectionEventDispatcher? collectionEventDispatcher)
+        public static NotifyCollectionChangedSynchronizedViewList<TView> ToNotifyCollectionChanged<T, TView>(this IObservableCollection<T> collection, Func<T, TView> transform, ICollectionEventDispatcher? collectionEventDispatcher)
         {
             // Optimized for non filtered
             return new NonFilteredSynchronizedViewList<T, TView>(collection.CreateView(transform), isSupportRangeFeature: false, collectionEventDispatcher, null);
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/ObservableCollections/ObservableList.OptimizeView.cs b/src/ObservableCollections/ObservableList.OptimizeView.cs
index b2a6df6..af48818 100644
--- a/src/ObservableCollections/ObservableList.OptimizeView.cs
+++ b/src/ObservableCollections/ObservableList.OptimizeView.cs
@@ -189,6 +189,25 @@ internal sealed class ObservableListSynchronizedViewList<T> : NotifyCollectionCh
     {
         parent.Add(item);
     }
+    public override void Insert(int index, T item)
+    {
+        parent.Insert(index, item);
+    }
+
+    public override bool Remove(T item)
+    {
+        return parent.Remove(item);
+    }
+
+    public override void RemoveAt(int index)
+    {
+        parent.RemoveAt(index);
+    }
+
+    public override void Clear()
+    {
+        parent.Clear();
+    }
 
     public override bool Contains(T item)
     {
@@ -199,4 +218,4 @@ internal sealed class ObservableListSynchronizedViewList<T> : NotifyCollectionCh
     {
         return parent.IndexOf(item);
     }
-}
\ No newline at end of file
+}
diff --git a/src/ObservableCollections/ObservableList.Views.cs b/src/ObservableCollections/ObservableList.Views.cs
index f4e35f2..e3b9498 100644
--- a/src/ObservableCollections/ObservableList.Views.cs
+++ b/src/ObservableCollections/ObservableList.Views.cs
@@ -19,12 +19,12 @@ namespace ObservableCollections
             return new View<TView>(this, transform);
         }
 
-        public INotifyCollectionChangedSynchronizedViewList<T> ToWritableNotifyCollectionChanged()
+        public NotifyCollectionChangedSynchronizedViewList<T> ToWritableNotifyCollectionChanged()
         {
             return ToWritableNotifyCollectionChanged(null);
         }
 
-        public INotifyCollectionChangedSynchronizedViewList<T> ToWritableNotifyCollectionChanged(ICollectionEventDispatcher? collectionEventDispatcher)
+        public NotifyCollectionChangedSynchronizedViewList<T> ToWritableNotifyCollectionChanged(ICollectionEventDispatcher? collectionEventDispatcher)
         {
             return ToWritableNotifyCollectionChanged(
                 static x => x,
@@ -36,12 +36,12 @@ namespace ObservableCollections
                 collectionEventDispatcher);
         }
 
-        public INotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged<TView>(Func<T, TView> transform, WritableViewChangedEventHandler<T, TView>? converter)
+        public NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged<TView>(Func<T, TView> transform, WritableViewChangedEventHandler<T, TView>? converter)
         {
             return ToWritableNotifyCollectionChanged(transform, converter, null!);
         }
 
-        public INotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged<TView>(Func<T, TView> transform, WritableViewChangedEventHandler<T, TView>? converter, ICollectionEventDispatcher? collectionEventDispatcher)
+        public NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged<TView>(Func<T, TView> transform, WritableViewChangedEventHandler<T, TView>? converter, ICollectionEventDispatcher? collectionEventDispatcher)
         {
             return new NonFilteredSynchronizedViewList<T, TView>(CreateView(transform), isSupportRangeFeature: false, collectionEventDispatcher, converter);
         }
@@ -367,12 +367,54 @@ namespace ObservableCollections
                     source.Add(value);
                 }
             }
+            public void InsertIntoSourceCollection(int index, T value)
+            {
+                lock (SyncRoot)
+                {
+                    source.Insert(index, value);
+                }
+            }
+
+            public bool RemoveFromSourceCollection(T value)
+            {
+                lock (SyncRoot)
+                {
+                    return source.Remove(value);
+                }
+            }
+
+            public void RemoveAtSourceCollection(int index)
+            {
+                lock (SyncRoot)
+                {
+                    source.RemoveAt(index);
+                }
+            }
+
+            public void ClearSourceCollection()
+            {
+                lock (SyncRoot)
+                {
+                    source.Clear();
+                }
+            }
 
             public IWritableSynchronizedViewList<TView> ToWritableViewList(WritableViewChangedEventHandler<T, TView> converter)
             {
                 return new FiltableSynchronizedViewList<T, TView>(this, isSupportRangeFeature: true, converter: converter);
             }
 
+            public NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged()
+            {
+                return new FiltableSynchronizedViewList<T, TView>(this,
+                    isSupportRangeFeature: false,
+                    converter: static (TView newView, T originalValue, ref bool setValue) =>
+                                {
+                                    setValue = true;
+                                    return originalValue;
+                                });
+            }
+
             public NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged(WritableViewChangedEventHandler<T, TView> converter)
             {
                 return new FiltableSynchronizedViewList<T, TView>(this, isSupportRangeFeature: false, converter: converter);
@@ -382,12 +424,12 @@ namespace ObservableCollections
             {
                 return new FiltableSynchronizedViewList<T, TView>(this,
                     isSupportRangeFeature: false,
-                    collectionEventDispatcher,
-                    static (TView newView, T originalValue, ref bool setValue) =>
-                    {
-                        setValue = true;
-                        return originalValue;
-                    });
+                    eventDispatcher: collectionEventDispatcher,
+                    converter: static (TView newView, T originalValue, ref bool setValue) =>
+                                {
+                                    setValue = true;
+                                    return originalValue;
+                                });
             }
 
             public NotifyCollectionChangedSynchronizedViewList<TView> ToWritableNotifyCollectionChanged(WritableViewChangedEventHandler<T, TView> converter, ICollectionEventDispatcher? collectionEventDispatcher)
diff --git a/src/ObservableCollections/SynchronizedViewList.cs b/src/ObservableCollections/SynchronizedViewList.cs
index e6c6c2d..c936b2c 100644
--- a/src/ObservableCollections/SynchronizedViewList.cs
+++ b/src/ObservableCollections/SynchronizedViewList.cs
@@ -337,21 +337,22 @@ internal sealed class FiltableSynchronizedViewList<T, TView> : NotifyCollectionC
         }
         set
         {
-            if (converter == null || parent is not IWritableSynchronizedView<T, TView> writableView)
+            if (IsReadOnly)
             {
-                throw new NotSupportedException("This CollectionView does not support set. If base type is ObservableList<T>, you can use ToWritableSynchronizedView and ToWritableNotifyCollectionChanged.");
+                throw new NotSupportedException("This CollectionView does not support Set. If base type is ObservableList<T>, you can use CreateWritableView and ToWritableNotifyCollectionChanged.");
             }
             else
             {
+                var writableView = parent as IWritableSynchronizedView<T, TView>;
                 var originalIndex = listView.GetAlternateIndex(index);
-                var (originalValue, _) = writableView.GetAt(originalIndex);
+                var (originalValue, _) = writableView!.GetAt(originalIndex);
 
                 // update view
                 writableView.SetViewAt(originalIndex, value);
                 listView[index] = value;
 
                 var setValue = true;
-                var newOriginal = converter(value, originalValue, ref setValue);
+                var newOriginal = converter!(value, originalValue, ref setValue);
 
                 if (setValue)
                 {
@@ -372,6 +373,8 @@ internal sealed class FiltableSynchronizedViewList<T, TView> : NotifyCollectionC
         }
     }
 
+    public override bool IsReadOnly => converter == null || parent is not IWritableSynchronizedView<T, TView>;
+
     public override IEnumerator<TView> GetEnumerator()
     {
         lock (gate)
@@ -385,17 +388,91 @@ internal sealed class FiltableSynchronizedViewList<T, TView> : NotifyCollectionC
 
     public override void Add(TView item)
     {
-        if (converter == null || parent is not IWritableSynchronizedView<T, TView> writableView)
+        if (IsReadOnly)
         {
-            throw new NotSupportedException("This CollectionView does not support Add. If base type is ObservableList<T>, you can use ToWritableSynchronizedView and ToWritableNotifyCollectionChanged.");
+            throw new NotSupportedException("This CollectionView does not support Add. If base type is ObservableList<T>, you can use CreateWritableView and ToWritableNotifyCollectionChanged.");
         }
         else
         {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            if (typeof(T) == typeof(TView) && item is T tItem)
+            {
+                writableView!.AddToSourceCollection(tItem);
+                return;
+            }
             var setValue = false;
-            var newOriginal = converter(item, default!, ref setValue);
+            var newOriginal = converter!(item, default!, ref setValue);
 
             // always add
-            writableView.AddToSourceCollection(newOriginal);
+            writableView!.AddToSourceCollection(newOriginal);
+        }
+    }
+
+    public override void Insert(int index, TView item)
+    {
+        if (IsReadOnly)
+        {
+            throw new NotSupportedException("This CollectionView does not support Insert. If base type is ObservableList<T>, you can use CreateWritableView and ToWritableNotifyCollectionChanged.");
+        }
+        else
+        {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            if (typeof(T) == typeof(TView) && item is T tItem)
+            {
+                writableView!.InsertIntoSourceCollection(index, tItem);
+                return;
+            }
+            var setValue = false;
+            var newOriginal = converter!(item, default!, ref setValue);
+
+            writableView!.InsertIntoSourceCollection(index, newOriginal);
+        }
+    }
+
+    public override bool Remove(TView item)
+    {
+        if (IsReadOnly)
+        {
+            throw new NotSupportedException("This CollectionView does not support Remove. If base type is ObservableList<T>, you can use CreateWritableView and ToWritableNotifyCollectionChanged.");
+        }
+        else
+        {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            if (typeof(T) == typeof(TView) && item is T tItem)
+            {
+                return writableView!.RemoveFromSourceCollection(tItem);
+            }
+            var setValue = false;
+            var newOriginal = converter!(item, default!, ref setValue);
+
+            // always add
+            return writableView!.RemoveFromSourceCollection(newOriginal);
+        }
+    }
+
+    public override void RemoveAt(int index)
+    {
+        if (IsReadOnly)
+        {
+            throw new NotSupportedException("This CollectionView does not support RemoveAt. If base type is ObservableList<T>, you can use CreateWritableView and ToWritableNotifyCollectionChanged.");
+        }
+        else
+        {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            writableView!.RemoveAtSourceCollection(index);
+        }
+    }
+
+    public override void Clear()
+    {
+        if (IsReadOnly)
+        {
+            throw new NotSupportedException("This CollectionView does not support Clear. If base type is ObservableList<T>, you can use CreateWritableView and ToWritableNotifyCollectionChanged.");
+        }
+        else
+        {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            writableView!.ClearSourceCollection();
         }
     }
 
@@ -762,20 +839,21 @@ internal sealed class NonFilteredSynchronizedViewList<T, TView> : NotifyCollecti
         }
         set
         {
-            if (converter == null || parent is not IWritableSynchronizedView<T, TView> writableView)
+            if (IsReadOnly)
             {
-                throw new NotSupportedException("This CollectionView does not support set. If base type is ObservableList<T>, you can use ToWritableSynchronizedView and ToWritableNotifyCollectionChanged.");
+                throw new NotSupportedException("This CollectionView does not support set. If base type is ObservableList<T>, you can use ToWritableNotifyCollectionChanged.");
             }
             else
             {
-                var (originalValue, _) = writableView.GetAt(index);
+                var writableView = parent as IWritableSynchronizedView<T, TView>;
+                var (originalValue, _) = writableView!.GetAt(index);
 
                 // update view
                 writableView.SetViewAt(index, value);
                 listView[index] = value;
 
                 var setValue = true;
-                var newOriginal = converter(value, originalValue, ref setValue);
+                var newOriginal = converter!(value, originalValue, ref setValue);
 
                 if (setValue)
                 {
@@ -796,6 +874,8 @@ internal sealed class NonFilteredSynchronizedViewList<T, TView> : NotifyCollecti
         }
     }
 
+    public override bool IsReadOnly => converter == null || parent is not IWritableSynchronizedView<T, TView>;
+
     public override IEnumerator<TView> GetEnumerator()
     {
         lock (gate)
@@ -809,17 +889,91 @@ internal sealed class NonFilteredSynchronizedViewList<T, TView> : NotifyCollecti
 
     public override void Add(TView item)
     {
-        if (converter == null || parent is not IWritableSynchronizedView<T, TView> writableView)
+        if (IsReadOnly)
         {
-            throw new NotSupportedException("This CollectionView does not support Add. If base type is ObservableList<T>, you can use ToWritableSynchronizedView and ToWritableNotifyCollectionChanged.");
+            throw new NotSupportedException("This CollectionView does not support Add. If base type is ObservableList<T>, you can use ToWritableNotifyCollectionChanged.");
         }
         else
         {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            if (typeof(T) == typeof(TView) && item is T tItem)
+            {
+                writableView!.AddToSourceCollection(tItem);
+                return;
+            }
             var setValue = false;
-            var newOriginal = converter(item, default!, ref setValue);
+            var newOriginal = converter!(item, default!, ref setValue);
 
             // always add
-            writableView.AddToSourceCollection(newOriginal);
+            writableView!.AddToSourceCollection(newOriginal);
+        }
+    }
+
+    public override void Insert(int index, TView item)
+    {
+        if (IsReadOnly)
+        {
+            throw new NotSupportedException("This CollectionView does not support Insert. If base type is ObservableList<T>, you can use ToWritableNotifyCollectionChanged.");
+        }
+        else
+        {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            if (typeof(T) == typeof(TView) && item is T tItem)
+            {
+                writableView!.InsertIntoSourceCollection(index, tItem);
+                return;
+            }
+            var setValue = false;
+            var newOriginal = converter!(item, default!, ref setValue);
+
+            writableView!.InsertIntoSourceCollection(index, newOriginal);
+        }
+    }
+
+    public override bool Remove(TView item)
+    {
+        if (IsReadOnly)
+        {
+            throw new NotSupportedException("This CollectionView does not support Remove. If base type is ObservableList<T>, you can use ToWritableNotifyCollectionChanged.");
+        }
+        else
+        {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            if (typeof(T) == typeof(TView) && item is T tItem)
+            {
+                return writableView!.RemoveFromSourceCollection(tItem);
+            }
+            var setValue = false;
+            var newOriginal = converter!(item, default!, ref setValue);
+
+            // always add
+            return writableView!.RemoveFromSourceCollection(newOriginal);
+        }
+    }
+
+    public override void RemoveAt(int index)
+    {
+        if (IsReadOnly)
+        {
+            throw new NotSupportedException("This CollectionView does not support RemoveAt. If base type is ObservableList<T>, you can use ToWritableNotifyCollectionChanged.");
+        }
+        else
+        {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            writableView!.RemoveAtSourceCollection(index);
+        }
+    }
+
+    public override void Clear()
+    {
+        if (IsReadOnly)
+        {
+            throw new NotSupportedException("This CollectionView does not support Clear. If base type is ObservableList<T>, you can use ToWritableNotifyCollectionChanged.");
+        }
+        else
+        {
+            var writableView = parent as IWritableSynchronizedView<T, TView>;
+            writableView!.ClearSourceCollection();
         }
     }
 
@@ -860,4 +1014,4 @@ internal sealed class NonFilteredSynchronizedViewList<T, TView> : NotifyCollecti
         parent.ViewChanged -= Parent_ViewChanged;
         parent.Dispose(); // Dispose parent
     }
-}
\ No newline at end of file
+}