diff --git a/src/ObservableCollections/Internal/NotifyCollectionChangedSynchronizedView.cs b/src/ObservableCollections/Internal/NotifyCollectionChangedSynchronizedView.cs
index d28aea7..6dc5974 100644
--- a/src/ObservableCollections/Internal/NotifyCollectionChangedSynchronizedView.cs
+++ b/src/ObservableCollections/Internal/NotifyCollectionChangedSynchronizedView.cs
@@ -1,8 +1,9 @@
-using System;
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
+using System.Linq;
 
 namespace ObservableCollections.Internal
 {
@@ -25,7 +26,7 @@ public NotifyCollectionChangedSynchronizedView(ISynchronizedView<T, TView> paren
             parent.AttachFilter(this);
         }
 
-        public int Count => parent.Count;
+        public virtual int Count => parent.Count;
 
         public event NotifyCollectionChangedEventHandler? CollectionChanged;
         public event PropertyChangedEventHandler? PropertyChanged;
@@ -152,7 +153,19 @@ public TView this[int index]
             {
                 lock (view.SyncRoot)
                 {
-                    return view.list[index].Item2;
+                    int currentIndex = 0;
+                    foreach (var (value, itemView) in view.list)
+                    {
+                        if (view.CurrentFilter.IsMatch(value, itemView))
+                        {
+                            if (currentIndex == index)
+                            {
+                                return itemView;
+                            }
+                            currentIndex++;
+                        }
+                    }
+                    throw new ArgumentOutOfRangeException(nameof(index));
                 }
             }
             set => throw new NotSupportedException();
@@ -162,14 +175,40 @@ public TView this[int index]
         {
             get
             {
-                return this[index];
+                lock (view.SyncRoot)
+                {
+                    int currentIndex = 0;
+                    foreach (var (value, itemView) in view.list)
+                    {
+                        if (view.CurrentFilter.IsMatch(value, itemView))
+                        {
+                            if (currentIndex == index)
+                            {
+                                return itemView;
+                            }
+                            currentIndex++;
+                        }
+                    }
+                    throw new ArgumentOutOfRangeException(nameof(index));
+                }
             }
             set => throw new NotSupportedException();
         }
 
+        public override int Count
+        {
+            get
+            {
+                lock (view.SyncRoot)
+                {
+                    return view.list.Count(item => view.CurrentFilter.IsMatch(item.Item1, item.Item2));
+                }
+            }
+        }
+
         static bool IsCompatibleObject(object? value)
         {
-            return (value is T) || (value == null && default(T) == null);
+            return (value is T) || (value is TView) || (value == null && default(T) == null);
         }
 
         public bool IsReadOnly => true;
@@ -199,11 +238,14 @@ public bool Contains(TView item)
         {
             lock (view.SyncRoot)
             {
-                foreach (var listItem in view.list)
+                foreach (var (value, itemView) in view.list)
                 {
-                    if (EqualityComparer<TView>.Default.Equals(listItem.Item2, item))
+                    if (view.CurrentFilter.IsMatch(value, itemView))
                     {
-                        return true;
+                        if (EqualityComparer<TView>.Default.Equals(itemView, item))
+                        {
+                            return true;
+                        }
                     }
                 }
             }
@@ -234,13 +276,16 @@ public int IndexOf(TView item)
             lock (view.SyncRoot)
             {
                 var index = 0;
-                foreach (var listItem in view.list)
+                foreach (var (value, itemView) in view.list)
                 {
-                    if (EqualityComparer<TView>.Default.Equals(listItem.Item2, item))
+                    if (view.CurrentFilter.IsMatch(value, itemView))
                     {
-                        return index;
+                        if (EqualityComparer<TView>.Default.Equals(itemView, item))
+                        {
+                            return index;
+                        }
+                        index++;
                     }
-                    index++;
                 }
             }
             return -1;
@@ -280,4 +325,4 @@ public void RemoveAt(int index)
             throw new NotSupportedException();
         }
     }
-}
\ No newline at end of file
+}