diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/FreezedView.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/FreezedView.cs
index 1c5f909..710428c 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/FreezedView.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/FreezedView.cs
@@ -67,13 +67,28 @@ namespace ObservableCollections.Internal
 
         public IEnumerator<(T, TView)> GetEnumerator()
         {
-            if (!reverse)
+            lock (SyncRoot)
             {
-                return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.GetEnumerator(), filter);
-            }
-            else
-            {
-                return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.AsEnumerable().Reverse().GetEnumerator(), filter);
+                if (!reverse)
+                {
+                    foreach (var item in list)
+                    {
+                        if (filter.IsMatch(item.Item1, item.Item2))
+                        {
+                            yield return item;
+                        }
+                    }
+                }
+                else
+                {
+                    foreach (var item in list.AsEnumerable().Reverse())
+                    {
+                        if (filter.IsMatch(item.Item1, item.Item2))
+                        {
+                            yield return item;
+                        }
+                    }
+                }
             }
         }
 
@@ -147,7 +162,16 @@ namespace ObservableCollections.Internal
 
         public IEnumerator<(T, TView)> GetEnumerator()
         {
-            return new SynchronizedViewEnumerator<T, TView>(SyncRoot, array.AsEnumerable().GetEnumerator(), filter);
+            lock (SyncRoot)
+            {
+                foreach (var item in array)
+                {
+                    if (filter.IsMatch(item.Item1, item.Item2))
+                    {
+                        yield return item;
+                    }
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SortedView.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SortedView.cs
index 1d4a0c0..d0ca75c 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SortedView.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SortedView.cs
@@ -88,7 +88,16 @@ namespace ObservableCollections.Internal
 
         public IEnumerator<(T, TView)> GetEnumerator()
         {
-            return new SynchronizedViewEnumerator<T, TView>(SyncRoot, dict.Select(x => x.Value).GetEnumerator(), filter);
+            lock (SyncRoot)
+            {
+                foreach (var item in dict)
+                {
+                    if (filter.IsMatch(item.Value.Value, item.Value.View))
+                    {
+                        yield return item.Value;
+                    }
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SortedViewViewComparer.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SortedViewViewComparer.cs
index 105edb6..c543490 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SortedViewViewComparer.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SortedViewViewComparer.cs
@@ -13,7 +13,7 @@ namespace ObservableCollections.Internal
         readonly Func<T, TView> transform;
         readonly Func<T, TKey> identitySelector;
         readonly Dictionary<TKey, TView> viewMap; // view-map needs to use in remove.
-        readonly SortedDictionary<(TView View, TKey Key), (T Value, TView View)> list;
+        readonly SortedDictionary<(TView View, TKey Key), (T Value, TView View)> dict;
 
         ISynchronizedViewFilter<T, TView> filter;
 
@@ -39,7 +39,7 @@ namespace ObservableCollections.Internal
                     dict.Add((view, id), (value, view));
                     viewMap.Add(id, view);
                 }
-                this.list = dict;
+                this.dict = dict;
                 this.source.CollectionChanged += SourceCollectionChanged;
             }
         }
@@ -50,7 +50,7 @@ namespace ObservableCollections.Internal
             {
                 lock (SyncRoot)
                 {
-                    return list.Count;
+                    return dict.Count;
                 }
             }
         }
@@ -60,7 +60,7 @@ namespace ObservableCollections.Internal
             lock (SyncRoot)
             {
                 this.filter = filter;
-                foreach (var (_, (value, view)) in list)
+                foreach (var (_, (value, view)) in dict)
                 {
                     filter.InvokeOnAttach(value, view);
                 }
@@ -74,7 +74,7 @@ namespace ObservableCollections.Internal
                 this.filter = SynchronizedViewFilter<T, TView>.Null;
                 if (resetAction != null)
                 {
-                    foreach (var (_, (value, view)) in list)
+                    foreach (var (_, (value, view)) in dict)
                     {
                         resetAction(value, view);
                     }
@@ -92,7 +92,17 @@ namespace ObservableCollections.Internal
 
         public IEnumerator<(T, TView)> GetEnumerator()
         {
-            return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.Select(x => x.Value).GetEnumerator(), filter);
+
+            lock (SyncRoot)
+            {
+                foreach (var item in dict)
+                {
+                    if (filter.IsMatch(item.Value.Value, item.Value.View))
+                    {
+                        yield return item.Value;
+                    }
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
@@ -116,7 +126,7 @@ namespace ObservableCollections.Internal
                                 var value = e.NewItem;
                                 var view = transform(value);
                                 var id = identitySelector(value);
-                                list.Add((view, id), (value, view));
+                                dict.Add((view, id), (value, view));
                                 viewMap.Add(id, view);
                                 filter.InvokeOnAdd(value, view);
                             }
@@ -126,7 +136,7 @@ namespace ObservableCollections.Internal
                                 {
                                     var view = transform(value);
                                     var id = identitySelector(value);
-                                    list.Add((view, id), (value, view));
+                                    dict.Add((view, id), (value, view));
                                     viewMap.Add(id, view);
                                     filter.InvokeOnAdd(value, view);
                                 }
@@ -141,7 +151,7 @@ namespace ObservableCollections.Internal
                                 var id = identitySelector(value);
                                 if (viewMap.Remove(id, out var view))
                                 {
-                                    list.Remove((view, id), out var v);
+                                    dict.Remove((view, id), out var v);
                                     filter.InvokeOnRemove(v);
                                 }
                             }
@@ -152,7 +162,7 @@ namespace ObservableCollections.Internal
                                     var id = identitySelector(value);
                                     if (viewMap.Remove(id, out var view))
                                     {
-                                        list.Remove((view, id), out var v);
+                                        dict.Remove((view, id), out var v);
                                         filter.InvokeOnRemove(v);
                                     }
                                 }
@@ -166,14 +176,14 @@ namespace ObservableCollections.Internal
                             var oldKey = identitySelector(oldValue);
                             if (viewMap.Remove(oldKey, out var oldView))
                             {
-                                list.Remove((oldView, oldKey));
+                                dict.Remove((oldView, oldKey));
                                 filter.InvokeOnRemove(oldValue, oldView);
                             }
 
                             var value = e.NewItem;
                             var view = transform(value);
                             var id = identitySelector(value);
-                            list.Add((view, id), (value, view));
+                            dict.Add((view, id), (value, view));
                             viewMap.Add(id, view);
 
                             filter.InvokeOnAdd(value, view);
@@ -193,12 +203,12 @@ namespace ObservableCollections.Internal
                     case NotifyCollectionChangedAction.Reset:
                         if (!filter.IsNullFilter())
                         {
-                            foreach (var item in list)
+                            foreach (var item in dict)
                             {
                                 filter.InvokeOnRemove(item.Value);
                             }
                         }
-                        list.Clear();
+                        dict.Clear();
                         viewMap.Clear();
                         break;
                     default:
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedEnumerator.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedEnumerator.cs
deleted file mode 100644
index 79948a4..0000000
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedEnumerator.cs
+++ /dev/null
@@ -1,46 +0,0 @@
-using System.Collections;
-using System.Collections.Generic;
-using System.Threading;
-
-namespace ObservableCollections.Internal
-{
-    internal class SynchronizedEnumerator<T> : IEnumerator<T>
-    {
-        bool isDisposed;
-        readonly object gate;
-        readonly bool lockTaken;
-        readonly IEnumerator<T> enumerator;
-
-        public SynchronizedEnumerator(object gate, IEnumerator<T> enumerator)
-        {
-            this.gate = gate;
-            this.enumerator = enumerator;
-            Monitor.Enter(gate, ref lockTaken);
-        }
-
-        public T Current => enumerator.Current;
-
-        object IEnumerator.Current => Current;
-        public bool MoveNext() => enumerator.MoveNext();
-        public void Reset() => enumerator.Reset();
-
-        public void Dispose()
-        {
-            if (!isDisposed)
-            {
-                isDisposed = true;
-                try
-                {
-                    enumerator.Dispose();
-                }
-                finally
-                {
-                    if (lockTaken)
-                    {
-                        Monitor.Exit(gate);
-                    }
-                }
-            }
-        }
-    }
-}
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedEnumerator.cs.meta b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedEnumerator.cs.meta
deleted file mode 100644
index edc4c63..0000000
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedEnumerator.cs.meta
+++ /dev/null
@@ -1,11 +0,0 @@
-fileFormatVersion: 2
-guid: 08405416bc7c7e04e9bcaa4fa13c875f
-MonoImporter:
-  externalObjects: {}
-  serializedVersion: 2
-  defaultReferences: []
-  executionOrder: 0
-  icon: {instanceID: 0}
-  userData: 
-  assetBundleName: 
-  assetBundleVariant: 
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedViewEnumerator.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedViewEnumerator.cs
deleted file mode 100644
index fe0072e..0000000
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedViewEnumerator.cs
+++ /dev/null
@@ -1,63 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Threading;
-
-namespace ObservableCollections.Internal
-{
-    internal class SynchronizedViewEnumerator<T, TView> : IEnumerator<(T, TView)>, IDisposable
-    {
-        bool isDisposed;
-        readonly bool lockTaken;
-        readonly object gate;
-        readonly IEnumerator<(T, TView)> enumerator;
-        readonly ISynchronizedViewFilter<T, TView> filter;
-        (T, TView) current;
-
-        public SynchronizedViewEnumerator(object gate, IEnumerator<(T, TView)> enumerator, ISynchronizedViewFilter<T, TView> filter)
-        {
-            this.gate = gate;
-            this.enumerator = enumerator;
-            this.filter = filter;
-            this.current = default;
-            this.isDisposed = false;
-            Monitor.Enter(gate, ref lockTaken);
-        }
-
-        public (T, TView) Current => current;
-        object IEnumerator.Current => Current;
-
-        public bool MoveNext()
-        {
-            while (enumerator.MoveNext())
-            {
-                current = enumerator.Current;
-                if (filter.IsMatch(current.Item1, current.Item2))
-                {
-                    return true;
-                }
-            }
-            return false;
-        }
-        public void Reset() => throw new NotSupportedException();
-
-        public void Dispose()
-        {
-            if (!isDisposed)
-            {
-                isDisposed = true;
-                try
-                {
-                    enumerator.Dispose();
-                }
-                finally
-                {
-                    if (lockTaken)
-                    {
-                        Monitor.Exit(gate);
-                    }
-                }
-            }
-        }
-    }
-}
\ No newline at end of file
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedViewEnumerator.cs.meta b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedViewEnumerator.cs.meta
deleted file mode 100644
index f902998..0000000
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/Internal/SynchronizedViewEnumerator.cs.meta
+++ /dev/null
@@ -1,11 +0,0 @@
-fileFormatVersion: 2
-guid: 98be7e821cfba26469f0911671fb24b6
-MonoImporter:
-  externalObjects: {}
-  serializedVersion: 2
-  defaultReferences: []
-  executionOrder: 0
-  icon: {instanceID: 0}
-  userData: 
-  assetBundleName: 
-  assetBundleVariant: 
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableDictionary.Views.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableDictionary.Views.cs
index 0416c1b..37b9fa2 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableDictionary.Views.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableDictionary.Views.cs
@@ -103,9 +103,17 @@ namespace ObservableCollections
 
             public IEnumerator<(KeyValuePair<TKey, TValue>, TView)> GetEnumerator()
             {
-                return new SynchronizedViewEnumerator<KeyValuePair<TKey, TValue>, TView>(SyncRoot,
-                    dict.Select(x => (new KeyValuePair<TKey, TValue>(x.Key, x.Value.Item1), x.Value.Item2)).GetEnumerator(),
-                    filter);
+                lock (SyncRoot)
+                {
+                    foreach (var item in dict)
+                    {
+                        var v = (new KeyValuePair<TKey, TValue>(item.Key, item.Value.Item1), item.Value.Item2);
+                        if (filter.IsMatch(v.Item1, v.Item2))
+                        {
+                            yield return v;
+                        }
+                    }
+                }
             }
 
             IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableDictionary.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableDictionary.cs
index 6740dbd..5222fd8 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableDictionary.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableDictionary.cs
@@ -211,7 +211,13 @@ namespace ObservableCollections
 
         public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
         {
-            return new SynchronizedEnumerator<KeyValuePair<TKey, TValue>>(SyncRoot, dictionary.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in dictionary)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableFixedSizeRingBuffer.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableFixedSizeRingBuffer.cs
index f696896..02ef0b2 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableFixedSizeRingBuffer.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableFixedSizeRingBuffer.cs
@@ -280,7 +280,13 @@ namespace ObservableCollections
 
         public IEnumerator<T> GetEnumerator()
         {
-            return new SynchronizedEnumerator<T>(SyncRoot, buffer.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in buffer)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableHashSet.Views.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableHashSet.Views.cs
index c6448dc..cc215b2 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableHashSet.Views.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableHashSet.Views.cs
@@ -88,7 +88,16 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                return new SynchronizedViewEnumerator<T, TView>(SyncRoot, dict.Select(x => x.Value).GetEnumerator(), filter);
+                lock (SyncRoot)
+                {
+                    foreach (var item in dict)
+                    {
+                        if (filter.IsMatch(item.Value.Item1, item.Value.Item2))
+                        {
+                            yield return item.Value;
+                        }
+                    }
+                }
             }
 
             IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableHashSet.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableHashSet.cs
index 25a78b2..328dfdb 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableHashSet.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableHashSet.cs
@@ -247,7 +247,13 @@ namespace ObservableCollections
 
         public IEnumerator<T> GetEnumerator()
         {
-            return new SynchronizedEnumerator<T>(SyncRoot, set.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in set)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableList.Views.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableList.Views.cs
index 5f46579..28e005c 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableList.Views.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableList.Views.cs
@@ -90,13 +90,28 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                if (!reverse)
+                lock (SyncRoot)
                 {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.GetEnumerator(), filter);
-                }
-                else
-                {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.AsEnumerable().Reverse().GetEnumerator(), filter);
+                    if (!reverse)
+                    {
+                        foreach (var item in list)
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in list.AsEnumerable().Reverse())
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
                 }
             }
 
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableList.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableList.cs
index d3e6ba5..01bb71c 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableList.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableList.cs
@@ -139,7 +139,13 @@ namespace ObservableCollections
 
         public IEnumerator<T> GetEnumerator()
         {
-            return new SynchronizedEnumerator<T>(SyncRoot, list.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in list)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableQueue.Views.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableQueue.Views.cs
index d1c5aa8..0939e0a 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableQueue.Views.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableQueue.Views.cs
@@ -90,13 +90,28 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                if (!reverse)
+                lock (SyncRoot)
                 {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, queue.GetEnumerator(), filter);
-                }
-                else
-                {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, queue.AsEnumerable().Reverse().GetEnumerator(), filter);
+                    if (!reverse)
+                    {
+                        foreach (var item in queue)
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in queue.AsEnumerable().Reverse())
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
                 }
             }
 
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableQueue.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableQueue.cs
index 010078e..f60d5d4 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableQueue.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableQueue.cs
@@ -203,7 +203,13 @@ namespace ObservableCollections
 
         public IEnumerator<T> GetEnumerator()
         {
-            return new SynchronizedEnumerator<T>(SyncRoot, queue.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in queue)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableRingBuffer.Views.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableRingBuffer.Views.cs
index 539b601..af5f857 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableRingBuffer.Views.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableRingBuffer.Views.cs
@@ -91,13 +91,28 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                if (!reverse)
+                lock (SyncRoot)
                 {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, ringBuffer.AsEnumerable().GetEnumerator(), filter);
-                }
-                else
-                {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, ringBuffer.AsEnumerable().Reverse().GetEnumerator(), filter);
+                    if (!reverse)
+                    {
+                        foreach (var item in ringBuffer)
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in ringBuffer.AsEnumerable().Reverse())
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
                 }
             }
 
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableRingBuffer.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableRingBuffer.cs
index 1301c75..4bd8c81 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableRingBuffer.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableRingBuffer.cs
@@ -195,7 +195,13 @@ namespace ObservableCollections
 
         public IEnumerator<T> GetEnumerator()
         {
-            return new SynchronizedEnumerator<T>(SyncRoot, buffer.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in buffer)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableStack.Views.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableStack.Views.cs
index 5e94caf..98157b6 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableStack.Views.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableStack.Views.cs
@@ -90,13 +90,28 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                if (!reverse)
+                lock (SyncRoot)
                 {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, stack.GetEnumerator(), filter);
-                }
-                else
-                {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, stack.AsEnumerable().Reverse().GetEnumerator(), filter);
+                    if (!reverse)
+                    {
+                        foreach (var item in stack)
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in stack.AsEnumerable().Reverse())
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
                 }
             }
 
diff --git a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableStack.cs b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableStack.cs
index 6f6748a..8d2dd60 100644
--- a/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableStack.cs
+++ b/src/ObservableCollections.Unity/Assets/Plugins/ObservableCollections/Runtime/ObservableStack.cs
@@ -199,7 +199,13 @@ namespace ObservableCollections
 
         public IEnumerator<T> GetEnumerator()
         {
-            return new SynchronizedEnumerator<T>(SyncRoot, stack.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in stack)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections/Internal/FreezedView.cs b/src/ObservableCollections/Internal/FreezedView.cs
index 0051081..95f7748 100644
--- a/src/ObservableCollections/Internal/FreezedView.cs
+++ b/src/ObservableCollections/Internal/FreezedView.cs
@@ -67,13 +67,28 @@ namespace ObservableCollections.Internal
 
         public IEnumerator<(T, TView)> GetEnumerator()
         {
-            if (!reverse)
+            lock (SyncRoot)
             {
-                return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.GetEnumerator(), filter);
-            }
-            else
-            {
-                return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.AsEnumerable().Reverse().GetEnumerator(), filter);
+                if (!reverse)
+                {
+                    foreach (var item in list)
+                    {
+                        if (filter.IsMatch(item.Item1, item.Item2))
+                        {
+                            yield return item;
+                        }
+                    }
+                }
+                else
+                {
+                    foreach (var item in list.AsEnumerable().Reverse())
+                    {
+                        if (filter.IsMatch(item.Item1, item.Item2))
+                        {
+                            yield return item;
+                        }
+                    }
+                }
             }
         }
 
@@ -147,7 +162,16 @@ namespace ObservableCollections.Internal
 
         public IEnumerator<(T, TView)> GetEnumerator()
         {
-            return new SynchronizedViewEnumerator<T, TView>(SyncRoot, array.AsEnumerable().GetEnumerator(), filter);
+            lock (SyncRoot)
+            {
+                foreach (var item in array)
+                {
+                    if (filter.IsMatch(item.Item1, item.Item2))
+                    {
+                        yield return item;
+                    }
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
diff --git a/src/ObservableCollections/Internal/SortedView.cs b/src/ObservableCollections/Internal/SortedView.cs
index 7aaa6c8..9dce18a 100644
--- a/src/ObservableCollections/Internal/SortedView.cs
+++ b/src/ObservableCollections/Internal/SortedView.cs
@@ -88,7 +88,16 @@ namespace ObservableCollections.Internal
 
         public IEnumerator<(T, TView)> GetEnumerator()
         {
-            return new SynchronizedViewEnumerator<T, TView>(SyncRoot, dict.Select(x => x.Value).GetEnumerator(), filter);
+            lock (SyncRoot)
+            {
+                foreach (var item in dict)
+                {
+                    if (filter.IsMatch(item.Value.Value, item.Value.View))
+                    {
+                        yield return item.Value;
+                    }
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
diff --git a/src/ObservableCollections/Internal/SortedViewViewComparer.cs b/src/ObservableCollections/Internal/SortedViewViewComparer.cs
index b8aad3e..3bf75b4 100644
--- a/src/ObservableCollections/Internal/SortedViewViewComparer.cs
+++ b/src/ObservableCollections/Internal/SortedViewViewComparer.cs
@@ -13,7 +13,7 @@ namespace ObservableCollections.Internal
         readonly Func<T, TView> transform;
         readonly Func<T, TKey> identitySelector;
         readonly Dictionary<TKey, TView> viewMap; // view-map needs to use in remove.
-        readonly SortedDictionary<(TView View, TKey Key), (T Value, TView View)> list;
+        readonly SortedDictionary<(TView View, TKey Key), (T Value, TView View)> dict;
 
         ISynchronizedViewFilter<T, TView> filter;
 
@@ -39,7 +39,7 @@ namespace ObservableCollections.Internal
                     dict.Add((view, id), (value, view));
                     viewMap.Add(id, view);
                 }
-                this.list = dict;
+                this.dict = dict;
                 this.source.CollectionChanged += SourceCollectionChanged;
             }
         }
@@ -50,7 +50,7 @@ namespace ObservableCollections.Internal
             {
                 lock (SyncRoot)
                 {
-                    return list.Count;
+                    return dict.Count;
                 }
             }
         }
@@ -60,7 +60,7 @@ namespace ObservableCollections.Internal
             lock (SyncRoot)
             {
                 this.filter = filter;
-                foreach (var (_, (value, view)) in list)
+                foreach (var (_, (value, view)) in dict)
                 {
                     filter.InvokeOnAttach(value, view);
                 }
@@ -74,7 +74,7 @@ namespace ObservableCollections.Internal
                 this.filter = SynchronizedViewFilter<T, TView>.Null;
                 if (resetAction != null)
                 {
-                    foreach (var (_, (value, view)) in list)
+                    foreach (var (_, (value, view)) in dict)
                     {
                         resetAction(value, view);
                     }
@@ -92,7 +92,17 @@ namespace ObservableCollections.Internal
 
         public IEnumerator<(T, TView)> GetEnumerator()
         {
-            return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.Select(x => x.Value).GetEnumerator(), filter);
+
+            lock (SyncRoot)
+            {
+                foreach (var item in dict)
+                {
+                    if (filter.IsMatch(item.Value.Value, item.Value.View))
+                    {
+                        yield return item.Value;
+                    }
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
@@ -116,7 +126,7 @@ namespace ObservableCollections.Internal
                                 var value = e.NewItem;
                                 var view = transform(value);
                                 var id = identitySelector(value);
-                                list.Add((view, id), (value, view));
+                                dict.Add((view, id), (value, view));
                                 viewMap.Add(id, view);
                                 filter.InvokeOnAdd(value, view);
                             }
@@ -126,7 +136,7 @@ namespace ObservableCollections.Internal
                                 {
                                     var view = transform(value);
                                     var id = identitySelector(value);
-                                    list.Add((view, id), (value, view));
+                                    dict.Add((view, id), (value, view));
                                     viewMap.Add(id, view);
                                     filter.InvokeOnAdd(value, view);
                                 }
@@ -141,7 +151,7 @@ namespace ObservableCollections.Internal
                                 var id = identitySelector(value);
                                 if (viewMap.Remove(id, out var view))
                                 {
-                                    list.Remove((view, id), out var v);
+                                    dict.Remove((view, id), out var v);
                                     filter.InvokeOnRemove(v);
                                 }
                             }
@@ -152,7 +162,7 @@ namespace ObservableCollections.Internal
                                     var id = identitySelector(value);
                                     if (viewMap.Remove(id, out var view))
                                     {
-                                        list.Remove((view, id), out var v);
+                                        dict.Remove((view, id), out var v);
                                         filter.InvokeOnRemove(v);
                                     }
                                 }
@@ -166,14 +176,14 @@ namespace ObservableCollections.Internal
                             var oldKey = identitySelector(oldValue);
                             if (viewMap.Remove(oldKey, out var oldView))
                             {
-                                list.Remove((oldView, oldKey));
+                                dict.Remove((oldView, oldKey));
                                 filter.InvokeOnRemove(oldValue, oldView);
                             }
 
                             var value = e.NewItem;
                             var view = transform(value);
                             var id = identitySelector(value);
-                            list.Add((view, id), (value, view));
+                            dict.Add((view, id), (value, view));
                             viewMap.Add(id, view);
 
                             filter.InvokeOnAdd(value, view);
@@ -193,12 +203,12 @@ namespace ObservableCollections.Internal
                     case NotifyCollectionChangedAction.Reset:
                         if (!filter.IsNullFilter())
                         {
-                            foreach (var item in list)
+                            foreach (var item in dict)
                             {
                                 filter.InvokeOnRemove(item.Value);
                             }
                         }
-                        list.Clear();
+                        dict.Clear();
                         viewMap.Clear();
                         break;
                     default:
diff --git a/src/ObservableCollections/Internal/SynchronizedViewEnumerator.cs b/src/ObservableCollections/Internal/SynchronizedViewEnumerator.cs
deleted file mode 100644
index 57fd267..0000000
--- a/src/ObservableCollections/Internal/SynchronizedViewEnumerator.cs
+++ /dev/null
@@ -1,63 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Threading;
-
-namespace ObservableCollections.Internal
-{
-    internal class SynchronizedViewEnumerator<T, TView> : IEnumerator<(T, TView)>, IDisposable
-    {
-        bool isDisposed;
-        readonly bool lockTaken;
-        readonly object gate;
-        readonly IEnumerator<(T, TView)> enumerator;
-        readonly ISynchronizedViewFilter<T, TView> filter;
-        (T, TView) current;
-
-        public SynchronizedViewEnumerator(object gate, IEnumerator<(T, TView)> enumerator, ISynchronizedViewFilter<T, TView> filter)
-        {
-            this.gate = gate;
-            this.enumerator = enumerator;
-            this.filter = filter;
-            this.current = default;
-            this.isDisposed = false;
-            Monitor.Enter(gate, ref lockTaken);
-        }
-
-        public (T, TView) Current => current;
-        object IEnumerator.Current => Current!;
-
-        public bool MoveNext()
-        {
-            while (enumerator.MoveNext())
-            {
-                current = enumerator.Current;
-                if (filter.IsMatch(current.Item1, current.Item2))
-                {
-                    return true;
-                }
-            }
-            return false;
-        }
-        public void Reset() => throw new NotSupportedException();
-
-        public void Dispose()
-        {
-            if (!isDisposed)
-            {
-                isDisposed = true;
-                try
-                {
-                    enumerator.Dispose();
-                }
-                finally
-                {
-                    if (lockTaken)
-                    {
-                        Monitor.Exit(gate);
-                    }
-                }
-            }
-        }
-    }
-}
\ No newline at end of file
diff --git a/src/ObservableCollections/ObservableDictionary.Views.cs b/src/ObservableCollections/ObservableDictionary.Views.cs
index 2bee71e..c8c00ea 100644
--- a/src/ObservableCollections/ObservableDictionary.Views.cs
+++ b/src/ObservableCollections/ObservableDictionary.Views.cs
@@ -103,9 +103,17 @@ namespace ObservableCollections
 
             public IEnumerator<(KeyValuePair<TKey, TValue>, TView)> GetEnumerator()
             {
-                return new SynchronizedViewEnumerator<KeyValuePair<TKey, TValue>, TView>(SyncRoot,
-                    dict.Select(x => (new KeyValuePair<TKey, TValue>(x.Key, x.Value.Item1), x.Value.Item2)).GetEnumerator(),
-                    filter);
+                lock (SyncRoot)
+                {
+                    foreach (var item in dict)
+                    {
+                        var v = (new KeyValuePair<TKey, TValue>(item.Key, item.Value.Item1), item.Value.Item2);
+                        if (filter.IsMatch(v.Item1, v.Item2))
+                        {
+                            yield return v;
+                        }
+                    }
+                }
             }
 
             IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections/ObservableHashSet.Views.cs b/src/ObservableCollections/ObservableHashSet.Views.cs
index 49450af..c054052 100644
--- a/src/ObservableCollections/ObservableHashSet.Views.cs
+++ b/src/ObservableCollections/ObservableHashSet.Views.cs
@@ -88,7 +88,16 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                return new SynchronizedViewEnumerator<T, TView>(SyncRoot, dict.Select(x => x.Value).GetEnumerator(), filter);
+                lock (SyncRoot)
+                {
+                    foreach (var item in dict)
+                    {
+                        if (filter.IsMatch(item.Value.Item1, item.Value.Item2))
+                        {
+                            yield return item.Value;
+                        }
+                    }
+                }
             }
 
             IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
diff --git a/src/ObservableCollections/ObservableHashSet.cs b/src/ObservableCollections/ObservableHashSet.cs
index 5ad41c6..b409515 100644
--- a/src/ObservableCollections/ObservableHashSet.cs
+++ b/src/ObservableCollections/ObservableHashSet.cs
@@ -247,7 +247,13 @@ namespace ObservableCollections
 
         public IEnumerator<T> GetEnumerator()
         {
-            return new SynchronizedEnumerator<T>(SyncRoot, set.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in set)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()
diff --git a/src/ObservableCollections/ObservableList.Views.cs b/src/ObservableCollections/ObservableList.Views.cs
index 0a503b6..282c390 100644
--- a/src/ObservableCollections/ObservableList.Views.cs
+++ b/src/ObservableCollections/ObservableList.Views.cs
@@ -90,13 +90,28 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                if (!reverse)
+                lock (SyncRoot)
                 {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.GetEnumerator(), filter);
-                }
-                else
-                {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, list.AsEnumerable().Reverse().GetEnumerator(), filter);
+                    if (!reverse)
+                    {
+                        foreach (var item in list)
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in list.AsEnumerable().Reverse())
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
                 }
             }
 
diff --git a/src/ObservableCollections/ObservableQueue.Views.cs b/src/ObservableCollections/ObservableQueue.Views.cs
index 82fc720..31db2f8 100644
--- a/src/ObservableCollections/ObservableQueue.Views.cs
+++ b/src/ObservableCollections/ObservableQueue.Views.cs
@@ -90,13 +90,28 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                if (!reverse)
+                lock (SyncRoot)
                 {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, queue.GetEnumerator(), filter);
-                }
-                else
-                {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, queue.AsEnumerable().Reverse().GetEnumerator(), filter);
+                    if (!reverse)
+                    {
+                        foreach (var item in queue)
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in queue.AsEnumerable().Reverse())
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
                 }
             }
 
diff --git a/src/ObservableCollections/ObservableRingBuffer.Views.cs b/src/ObservableCollections/ObservableRingBuffer.Views.cs
index 50df81e..b20a7b4 100644
--- a/src/ObservableCollections/ObservableRingBuffer.Views.cs
+++ b/src/ObservableCollections/ObservableRingBuffer.Views.cs
@@ -91,13 +91,28 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                if (!reverse)
+                lock (SyncRoot)
                 {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, ringBuffer.AsEnumerable().GetEnumerator(), filter);
-                }
-                else
-                {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, ringBuffer.AsEnumerable().Reverse().GetEnumerator(), filter);
+                    if (!reverse)
+                    {
+                        foreach (var item in ringBuffer)
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in ringBuffer.AsEnumerable().Reverse())
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
                 }
             }
 
diff --git a/src/ObservableCollections/ObservableStack.Views.cs b/src/ObservableCollections/ObservableStack.Views.cs
index 81cbf97..77ec33c 100644
--- a/src/ObservableCollections/ObservableStack.Views.cs
+++ b/src/ObservableCollections/ObservableStack.Views.cs
@@ -90,13 +90,28 @@ namespace ObservableCollections
 
             public IEnumerator<(T, TView)> GetEnumerator()
             {
-                if (!reverse)
+                lock (SyncRoot)
                 {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, stack.GetEnumerator(), filter);
-                }
-                else
-                {
-                    return new SynchronizedViewEnumerator<T, TView>(SyncRoot, stack.AsEnumerable().Reverse().GetEnumerator(), filter);
+                    if (!reverse)
+                    {
+                        foreach (var item in stack)
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
+                    else
+                    {
+                        foreach (var item in stack.AsEnumerable().Reverse())
+                        {
+                            if (filter.IsMatch(item.Item1, item.Item2))
+                            {
+                                yield return item;
+                            }
+                        }
+                    }
                 }
             }
 
diff --git a/src/ObservableCollections/ObservableStack.cs b/src/ObservableCollections/ObservableStack.cs
index e1d56e7..1847f3d 100644
--- a/src/ObservableCollections/ObservableStack.cs
+++ b/src/ObservableCollections/ObservableStack.cs
@@ -199,7 +199,13 @@ namespace ObservableCollections
 
         public IEnumerator<T> GetEnumerator()
         {
-            return new SynchronizedEnumerator<T>(SyncRoot, stack.GetEnumerator());
+            lock (SyncRoot)
+            {
+                foreach (var item in stack)
+                {
+                    yield return item;
+                }
+            }
         }
 
         IEnumerator IEnumerable.GetEnumerator()