diff --git a/src/DynamicData.Tests/API/ApiApprovalTests.DynamicDataTests.DotNet8_0.verified.txt b/src/DynamicData.Tests/API/ApiApprovalTests.DynamicDataTests.DotNet8_0.verified.txt
index 55e3576c..0bf3dba9 100644
--- a/src/DynamicData.Tests/API/ApiApprovalTests.DynamicDataTests.DotNet8_0.verified.txt
+++ b/src/DynamicData.Tests/API/ApiApprovalTests.DynamicDataTests.DotNet8_0.verified.txt
@@ -540,9 +540,9 @@ namespace DynamicData.Cache.Internal
         public LockFreeObservableCache(System.IObservable<DynamicData.IChangeSet<TObject, TKey>> source) { }
         public int Count { get; }
         public System.IObservable<int> CountChanged { get; }
-        public System.Collections.Generic.IEnumerable<TObject> Items { get; }
-        public System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey, TObject>> KeyValues { get; }
-        public System.Collections.Generic.IEnumerable<TKey> Keys { get; }
+        public System.Collections.Generic.IReadOnlyList<TObject> Items { get; }
+        public System.Collections.Generic.IReadOnlyDictionary<TKey, TObject> KeyValues { get; }
+        public System.Collections.Generic.IReadOnlyList<TKey> Keys { get; }
         public System.IObservable<DynamicData.IChangeSet<TObject, TKey>> Connect(System.Func<TObject, bool>? predicate = null, bool suppressEmptyChangeSets = true) { }
         public void Dispose() { }
         public void Edit(System.Action<DynamicData.ICacheUpdater<TObject, TKey>> editAction) { }
@@ -874,9 +874,9 @@ namespace DynamicData
         where TKey :  notnull
     {
         int Count { get; }
-        System.Collections.Generic.IEnumerable<TObject> Items { get; }
-        System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey, TObject>> KeyValues { get; }
-        System.Collections.Generic.IEnumerable<TKey> Keys { get; }
+        System.Collections.Generic.IReadOnlyList<TObject> Items { get; }
+        System.Collections.Generic.IReadOnlyDictionary<TKey, TObject> KeyValues { get; }
+        System.Collections.Generic.IReadOnlyList<TKey> Keys { get; }
         DynamicData.Kernel.Optional<TObject> Lookup(TKey key);
     }
     public interface IObservableList<T> : System.IDisposable
@@ -993,9 +993,9 @@ namespace DynamicData
         public IntermediateCache(System.IObservable<DynamicData.IChangeSet<TObject, TKey>> source) { }
         public int Count { get; }
         public System.IObservable<int> CountChanged { get; }
-        public System.Collections.Generic.IEnumerable<TObject> Items { get; }
-        public System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey, TObject>> KeyValues { get; }
-        public System.Collections.Generic.IEnumerable<TKey> Keys { get; }
+        public System.Collections.Generic.IReadOnlyList<TObject> Items { get; }
+        public System.Collections.Generic.IReadOnlyDictionary<TKey, TObject> KeyValues { get; }
+        public System.Collections.Generic.IReadOnlyList<TKey> Keys { get; }
         public System.IObservable<DynamicData.IChangeSet<TObject, TKey>> Connect(System.Func<TObject, bool>? predicate = null, bool suppressEmptyChangeSets = true) { }
         public void Dispose() { }
         public void Edit(System.Action<DynamicData.ICacheUpdater<TObject, TKey>> updateAction) { }
@@ -2610,10 +2610,10 @@ namespace DynamicData
         public SourceCache(System.Func<TObject, TKey> keySelector) { }
         public int Count { get; }
         public System.IObservable<int> CountChanged { get; }
-        public System.Collections.Generic.IEnumerable<TObject> Items { get; }
+        public System.Collections.Generic.IReadOnlyList<TObject> Items { get; }
         public System.Func<TObject, TKey> KeySelector { get; }
-        public System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey, TObject>> KeyValues { get; }
-        public System.Collections.Generic.IEnumerable<TKey> Keys { get; }
+        public System.Collections.Generic.IReadOnlyDictionary<TKey, TObject> KeyValues { get; }
+        public System.Collections.Generic.IReadOnlyList<TKey> Keys { get; }
         public System.IObservable<DynamicData.IChangeSet<TObject, TKey>> Connect(System.Func<TObject, bool>? predicate = null, bool suppressEmptyChangeSets = true) { }
         public void Dispose() { }
         public void Edit(System.Action<DynamicData.ISourceUpdater<TObject, TKey>> updateAction) { }
diff --git a/src/DynamicData.Tests/Cache/AndFixture.cs b/src/DynamicData.Tests/Cache/AndFixture.cs
index 9b447f20..0f0ec2ad 100644
--- a/src/DynamicData.Tests/Cache/AndFixture.cs
+++ b/src/DynamicData.Tests/Cache/AndFixture.cs
@@ -78,7 +78,7 @@ public void UpdatingBothProducesResults()
         _source2.AddOrUpdate(person);
         _results.Messages.Count.Should().Be(1, "Should have no updates");
         _results.Data.Count.Should().Be(1, "Cache should have no items");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -92,7 +92,7 @@ public void UpdatingOneProducesOnlyOneUpdate()
         _source2.AddOrUpdate(personUpdated);
         _results.Messages.Count.Should().Be(2, "Should be 2 updates");
         _results.Data.Count.Should().Be(1, "Cache should have no items");
-        _results.Data.Items.First().Should().Be(personUpdated, "Should be updated person");
+        _results.Data.Items[0].Should().Be(personUpdated, "Should be updated person");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/DisposeManyFixture.cs b/src/DynamicData.Tests/Cache/DisposeManyFixture.cs
index b15be5a6..b196e143 100644
--- a/src/DynamicData.Tests/Cache/DisposeManyFixture.cs
+++ b/src/DynamicData.Tests/Cache/DisposeManyFixture.cs
@@ -99,14 +99,14 @@ public void ItemsAreDisposedAfterRemovalOrReplacement()
         {
             new Change<DisposableObject, int>(
                 reason: ChangeReason.Refresh,
-                key: _itemsSource.Items.First().Id,
-                current: _itemsSource.Items.First())
+                key: _itemsSource.Items[0].Id,
+                current: _itemsSource.Items[0])
         });
         _changeSetsSource.OnNext(new ChangeSet<DisposableObject, int>() // Move
         {
             new Change<DisposableObject, int>(
-                key: _itemsSource.Items.First().Id,
-                current: _itemsSource.Items.First(),
+                key: _itemsSource.Items[0].Id,
+                current: _itemsSource.Items[0],
                 currentIndex: 1,
                 previousIndex: 0)
         });
diff --git a/src/DynamicData.Tests/Cache/DistinctFixture.cs b/src/DynamicData.Tests/Cache/DistinctFixture.cs
index 0363c0c5..fbbd36c7 100644
--- a/src/DynamicData.Tests/Cache/DistinctFixture.cs
+++ b/src/DynamicData.Tests/Cache/DistinctFixture.cs
@@ -64,7 +64,7 @@ public void DuplicatedResultsResultInNoAdditionalMessage()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 update message");
         _results.Data.Count.Should().Be(1, "Should be 1 items in the cache");
-        _results.Data.Items.First().Should().Be(20, "Should 20");
+        _results.Data.Items[0].Should().Be(20, "Should 20");
     }
 
     [Fact]
@@ -98,7 +98,7 @@ public void FiresAddWhenaNewItemIsAdded()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(20, "Should 20");
+        _results.Data.Items[0].Should().Be(20, "Should 20");
     }
 
     [Fact]
@@ -116,7 +116,7 @@ public void FiresBatchResultOnce()
         _results.Data.Count.Should().Be(3, "Should be 3 items in the cache");
 
         _results.Data.Items.Should().BeEquivalentTo(new[] { 20, 21, 22 });
-        _results.Data.Items.First().Should().Be(20, "Should 20");
+        _results.Data.Items[0].Should().Be(20, "Should 20");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/DynamicAndFixture.cs b/src/DynamicData.Tests/Cache/DynamicAndFixture.cs
index 6793616a..c9b79b54 100644
--- a/src/DynamicData.Tests/Cache/DynamicAndFixture.cs
+++ b/src/DynamicData.Tests/Cache/DynamicAndFixture.cs
@@ -108,7 +108,7 @@ public void UpdatingBothProducesResults()
         _source2.AddOrUpdate(person);
         _results.Messages.Count.Should().Be(1, "Should have no updates");
         _results.Data.Count.Should().Be(1, "Cache should have no items");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -125,7 +125,7 @@ public void UpdatingOneProducesOnlyOneUpdate()
         _source2.AddOrUpdate(personUpdated);
         _results.Messages.Count.Should().Be(2, "Should be 2 updates");
         _results.Data.Count.Should().Be(1, "Cache should have no items");
-        _results.Data.Items.First().Should().Be(personUpdated, "Should be updated person");
+        _results.Data.Items[0].Should().Be(personUpdated, "Should be updated person");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/DynamicOrFixture.cs b/src/DynamicData.Tests/Cache/DynamicOrFixture.cs
index 7b1b1005..d02c3764 100644
--- a/src/DynamicData.Tests/Cache/DynamicOrFixture.cs
+++ b/src/DynamicData.Tests/Cache/DynamicOrFixture.cs
@@ -108,7 +108,7 @@ public void UpdatingBothProducesResultsAndDoesNotDuplicateTheMessage()
         _source2.AddOrUpdate(person);
         _results.Messages.Count.Should().Be(1, "Should have no updates");
         _results.Data.Count.Should().Be(1, "Cache should have no items");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -125,7 +125,7 @@ public void UpdatingOneProducesOnlyOneUpdate()
         _source2.AddOrUpdate(personUpdated);
         _results.Messages.Count.Should().Be(2, "Should be 2 updates");
         _results.Data.Count.Should().Be(1, "Cache should have no items");
-        _results.Data.Items.First().Should().Be(personUpdated, "Should be updated person");
+        _results.Data.Items[0].Should().Be(personUpdated, "Should be updated person");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/FilterControllerFixture.cs b/src/DynamicData.Tests/Cache/FilterControllerFixture.cs
index 291ee700..ebe07324 100644
--- a/src/DynamicData.Tests/Cache/FilterControllerFixture.cs
+++ b/src/DynamicData.Tests/Cache/FilterControllerFixture.cs
@@ -37,7 +37,7 @@ public void AddMatched()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -66,7 +66,7 @@ public void AddNotMatchedAndUpdateMatched()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Messages[0].First().Current.Should().Be(matched, "Should be same person");
-        _results.Data.Items.First().Should().Be(matched, "Should be same person");
+        _results.Data.Items[0].Should().Be(matched, "Should be same person");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/FilterFixture.cs b/src/DynamicData.Tests/Cache/FilterFixture.cs
index 886ba188..9e901c8c 100644
--- a/src/DynamicData.Tests/Cache/FilterFixture.cs
+++ b/src/DynamicData.Tests/Cache/FilterFixture.cs
@@ -30,7 +30,7 @@ public void AddMatched()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -59,7 +59,7 @@ public void AddNotMatchedAndUpdateMatched()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Messages[0].First().Current.Should().Be(matched, "Should be same person");
-        _results.Data.Items.First().Should().Be(matched, "Should be same person");
+        _results.Data.Items[0].Should().Be(matched, "Should be same person");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/FilterParallelFixture.cs b/src/DynamicData.Tests/Cache/FilterParallelFixture.cs
index 14e7ed82..bc141168 100644
--- a/src/DynamicData.Tests/Cache/FilterParallelFixture.cs
+++ b/src/DynamicData.Tests/Cache/FilterParallelFixture.cs
@@ -30,7 +30,7 @@ public void AddMatched()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -59,7 +59,7 @@ public void AddNotMatchedAndUpdateMatched()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Messages[0].First().Current.Should().Be(matched, "Should be same person");
-        _results.Data.Items.First().Should().Be(matched, "Should be same person");
+        _results.Data.Items[0].Should().Be(matched, "Should be same person");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/GroupImmutableFixture.cs b/src/DynamicData.Tests/Cache/GroupImmutableFixture.cs
index 0ad2d5c6..8640bccb 100644
--- a/src/DynamicData.Tests/Cache/GroupImmutableFixture.cs
+++ b/src/DynamicData.Tests/Cache/GroupImmutableFixture.cs
@@ -102,7 +102,7 @@ public void FiresOnlyOnceForABatchOfUniqueValues()
 
         _results.Messages.Count.Should().Be(1);
         _results.Messages.First().Adds.Should().Be(1);
-        _results.Data.Items.First().Count.Should().Be(4);
+        _results.Data.Items[0].Count.Should().Be(4);
     }
 
     [Fact]
@@ -158,7 +158,7 @@ public void UpdateAnItemWillChangedThegroup()
         _results.Messages.First().Adds.Should().Be(1);
         _results.Messages.Skip(1).First().Adds.Should().Be(1);
         _results.Messages.Skip(1).First().Removes.Should().Be(1);
-        var group = _results.Data.Items.First();
+        var group = _results.Data.Items[0];
         group.Count.Should().Be(1);
 
         group.Key.Should().Be(21);
@@ -174,7 +174,7 @@ public void UpdatesArePermissible()
         _results.Messages.First().Adds.Should().Be(1);
         _results.Messages.Skip(1).First().Updates.Should().Be(1);
 
-        var group = _results.Data.Items.First();
+        var group = _results.Data.Items[0];
         group.Count.Should().Be(2);
     }
 }
diff --git a/src/DynamicData.Tests/Cache/GroupOnObservableFixture.cs b/src/DynamicData.Tests/Cache/GroupOnObservableFixture.cs
index 9c2fea74..3e8dd885 100644
--- a/src/DynamicData.Tests/Cache/GroupOnObservableFixture.cs
+++ b/src/DynamicData.Tests/Cache/GroupOnObservableFixture.cs
@@ -208,7 +208,7 @@ public void AllGroupsRemovedWhenCleared()
         _cache.Clear();
 
         // Assert
-        _cache.Items.Count().Should().Be(0);
+        _cache.Items.Count.Should().Be(0);
         _results.Messages.Count.Should().Be(2, "1 for Adds and 1 for Removes");
         _groupResults.Summary.Overall.Adds.Should().Be(colorCount);
         _groupResults.Summary.Overall.Removes.Should().Be(colorCount);
diff --git a/src/DynamicData.Tests/Cache/GroupOnPropertyFixture.cs b/src/DynamicData.Tests/Cache/GroupOnPropertyFixture.cs
index 89c84e8f..7af36211 100644
--- a/src/DynamicData.Tests/Cache/GroupOnPropertyFixture.cs
+++ b/src/DynamicData.Tests/Cache/GroupOnPropertyFixture.cs
@@ -28,7 +28,7 @@ public void CanGroupOnAdds()
 
         _results.Data.Count.Should().Be(1);
 
-        var firstGroup = _results.Data.Items.First();
+        var firstGroup = _results.Data.Items[0];
 
         firstGroup.Cache.Count.Should().Be(1);
         firstGroup.Key.Should().Be(10);
@@ -92,7 +92,7 @@ public void Regroup()
         person.Age = 20;
 
         _results.Data.Count.Should().Be(1);
-        var firstGroup = _results.Data.Items.First();
+        var firstGroup = _results.Data.Items[0];
 
         firstGroup.Cache.Count.Should().Be(1);
         firstGroup.Key.Should().Be(20);
diff --git a/src/DynamicData.Tests/Cache/GroupOnPropertyWithImmutableStateFixture.cs b/src/DynamicData.Tests/Cache/GroupOnPropertyWithImmutableStateFixture.cs
index 90ceb665..2321b6e3 100644
--- a/src/DynamicData.Tests/Cache/GroupOnPropertyWithImmutableStateFixture.cs
+++ b/src/DynamicData.Tests/Cache/GroupOnPropertyWithImmutableStateFixture.cs
@@ -29,7 +29,7 @@ public void CanGroupOnAdds()
 
         _results.Data.Count.Should().Be(1);
 
-        var firstGroup = _results.Data.Items.First();
+        var firstGroup = _results.Data.Items[0];
 
         firstGroup.Count.Should().Be(1);
         firstGroup.Key.Should().Be(10);
@@ -93,7 +93,7 @@ public void Regroup()
         person.Age = 20;
 
         _results.Data.Count.Should().Be(1);
-        var firstGroup = _results.Data.Items.First();
+        var firstGroup = _results.Data.Items[0];
 
         firstGroup.Count.Should().Be(1);
         firstGroup.Key.Should().Be(20);
diff --git a/src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheFixture.cs b/src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheFixture.cs
index 2dbc77f9..9d63b5b7 100644
--- a/src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheFixture.cs
+++ b/src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheFixture.cs
@@ -806,11 +806,11 @@ private void CheckResultContents(ChangeSetAggregator<IMarket, Guid> marketResult
 
         // These should be subsets of each other
         expectedMarkets.Should().BeSubsetOf(marketResults.Data.Items);
-        marketResults.Data.Items.Count().Should().Be(expectedMarkets.Count);
+        marketResults.Data.Items.Count.Should().Be(expectedMarkets.Count);
 
         // These should be subsets of each other
         expectedPrices.Should().BeSubsetOf(priceResults.Data.Items);
-        priceResults.Data.Items.Count().Should().Be(expectedPrices.Count);
+        priceResults.Data.Items.Count.Should().Be(expectedPrices.Count);
     }
 
     private void DisposeMarkets()
diff --git a/src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheSourceCompareFixture.cs b/src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheSourceCompareFixture.cs
index 98f6da4d..152cfe9e 100644
--- a/src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheSourceCompareFixture.cs
+++ b/src/DynamicData.Tests/Cache/MergeManyChangeSetsCacheSourceCompareFixture.cs
@@ -1074,7 +1074,7 @@ private void CheckResultContents(ChangeSetAggregator<IMarket, Guid> marketResult
 
         // These should be subsets of each other
         expectedMarkets.Should().BeSubsetOf(marketResults.Data.Items);
-        marketResults.Data.Items.Count().Should().Be(expectedMarkets.Count);
+        marketResults.Data.Items.Count.Should().Be(expectedMarkets.Count);
 
         // Pair up all the Markets/Prices, Group them by ItemId, and sort each Group by the Market comparer
         // Then pull out the first value from each group, which should be the price from the best market for each ItemId
@@ -1085,7 +1085,7 @@ private void CheckResultContents(ChangeSetAggregator<IMarket, Guid> marketResult
 
         // These should be subsets of each other
         expectedPrices.Should().BeSubsetOf(priceResults.Data.Items);
-        priceResults.Data.Items.Count().Should().Be(expectedPrices.Count);
+        priceResults.Data.Items.Count.Should().Be(expectedPrices.Count);
     }
 
     private void DisposeMarkets()
diff --git a/src/DynamicData.Tests/Cache/MergeManyChangeSetsListFixture.cs b/src/DynamicData.Tests/Cache/MergeManyChangeSetsListFixture.cs
index 1813b23e..f7a4aa2a 100644
--- a/src/DynamicData.Tests/Cache/MergeManyChangeSetsListFixture.cs
+++ b/src/DynamicData.Tests/Cache/MergeManyChangeSetsListFixture.cs
@@ -459,7 +459,7 @@ private static void CheckResultContents(IEnumerable<AnimalOwner> owners, ChangeS
 
         // These should be subsets of each other
         expectedOwners.Should().BeSubsetOf(ownerResults.Data.Items);
-        ownerResults.Data.Items.Count().Should().Be(expectedOwners.Count);
+        ownerResults.Data.Items.Count.Should().Be(expectedOwners.Count);
 
         // All owner animals should be in the results
         foreach (var owner in owners)
diff --git a/src/DynamicData.Tests/Cache/ObservableToObservableChangeSetFixture.cs b/src/DynamicData.Tests/Cache/ObservableToObservableChangeSetFixture.cs
index a750a008..d4e6ce03 100644
--- a/src/DynamicData.Tests/Cache/ObservableToObservableChangeSetFixture.cs
+++ b/src/DynamicData.Tests/Cache/ObservableToObservableChangeSetFixture.cs
@@ -123,7 +123,7 @@ public void OnNextFiresAdd()
 
         results.Messages.Count.Should().Be(1, "Should be 1 updates");
         results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        results.Data.Items.First().Should().Be(person, "Should be same person");
+        results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -141,7 +141,7 @@ public void OnNextForAmendedItemFiresUpdate()
         results.Messages.Count.Should().Be(2, "Should be 2 message");
         results.Messages[1].Updates.Should().Be(1, "Should be 1 updates");
         results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        results.Data.Items.First().Should().Be(personamend, "Should be same person");
+        results.Data.Items[0].Should().Be(personamend, "Should be same person");
     }
 
     [Fact]
@@ -155,6 +155,6 @@ public void OnNextProducesAndAddChangeForSingleItem()
 
         results.Messages.Count.Should().Be(1, "Should be 1 updates");
         results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        results.Data.Items.First().Should().Be(person, "Should be same person");
+        results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 }
diff --git a/src/DynamicData.Tests/Cache/OrFixture.cs b/src/DynamicData.Tests/Cache/OrFixture.cs
index 809d34dc..720d3f0b 100644
--- a/src/DynamicData.Tests/Cache/OrFixture.cs
+++ b/src/DynamicData.Tests/Cache/OrFixture.cs
@@ -67,7 +67,7 @@ public void UpdatingBothProducesResultsAndDoesNotDuplicateTheMessage()
         _source2.AddOrUpdate(person);
         _results.Messages.Count.Should().Be(1, "Should have no updates");
         _results.Data.Count.Should().Be(1, "Cache should have no items");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -81,7 +81,7 @@ public void UpdatingOneProducesOnlyOneUpdate()
         _source2.AddOrUpdate(personUpdated);
         _results.Messages.Count.Should().Be(2, "Should be 2 updates");
         _results.Data.Count.Should().Be(1, "Cache should have no items");
-        _results.Data.Items.First().Should().Be(personUpdated, "Should be updated person");
+        _results.Data.Items[0].Should().Be(personUpdated, "Should be updated person");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/RightJoinManyFixture.cs b/src/DynamicData.Tests/Cache/RightJoinManyFixture.cs
index 6f3c63bc..0f8dc894 100644
--- a/src/DynamicData.Tests/Cache/RightJoinManyFixture.cs
+++ b/src/DynamicData.Tests/Cache/RightJoinManyFixture.cs
@@ -51,7 +51,7 @@ public void AddLeftOnly()
         _people.AddOrUpdate(people);
 
         _result.Data.Count.Should().Be(1);
-        _result.Data.Items.First().Parent.Should().BeNull();
+        _result.Data.Items[0].Parent.Should().BeNull();
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/SizeLimitFixture.cs b/src/DynamicData.Tests/Cache/SizeLimitFixture.cs
index 2de5c165..bbc67f04 100644
--- a/src/DynamicData.Tests/Cache/SizeLimitFixture.cs
+++ b/src/DynamicData.Tests/Cache/SizeLimitFixture.cs
@@ -40,7 +40,7 @@ public void Add()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
@@ -53,7 +53,7 @@ public void AddLessThanLimit()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(person, "Should be same person");
+        _results.Data.Items[0].Should().Be(person, "Should be same person");
     }
 
     [Fact]
diff --git a/src/DynamicData.Tests/Cache/SortAndBindFixture.cs b/src/DynamicData.Tests/Cache/SortAndBindFixture.cs
index 723a39cd..db254be1 100644
--- a/src/DynamicData.Tests/Cache/SortAndBindFixture.cs
+++ b/src/DynamicData.Tests/Cache/SortAndBindFixture.cs
@@ -13,6 +13,19 @@
 
 namespace DynamicData.Tests.Cache;
 
+// Bind to a list
+public sealed class SortByAndBindToList : SortAndBindFixture
+
+{
+    protected override (ChangeSetAggregator<Person, string> Aggregrator, IList<Person> List) SetUpTests()
+    {
+        var list = new List<Person>(100);
+        var aggregator = _source.Connect().SortAndBind(list, _comparer).AsAggregator();
+
+        return (aggregator, list);
+    }
+}
+
 
 // Bind to a list
 public sealed class SortAndBindToList: SortAndBindFixture
diff --git a/src/DynamicData.Tests/Cache/SubscribeManyFixture.cs b/src/DynamicData.Tests/Cache/SubscribeManyFixture.cs
index 7e8423eb..5d6d2672 100644
--- a/src/DynamicData.Tests/Cache/SubscribeManyFixture.cs
+++ b/src/DynamicData.Tests/Cache/SubscribeManyFixture.cs
@@ -33,7 +33,7 @@ public void AddedItemWillbeSubscribed()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().IsSubscribed.Should().Be(true, "Should be subscribed");
+        _results.Data.Items[0].IsSubscribed.Should().Be(true, "Should be subscribed");
     }
 
     public void Dispose()
diff --git a/src/DynamicData.Tests/Cache/TransformAsyncFixture.cs b/src/DynamicData.Tests/Cache/TransformAsyncFixture.cs
index a8c4c3b0..a40356f4 100644
--- a/src/DynamicData.Tests/Cache/TransformAsyncFixture.cs
+++ b/src/DynamicData.Tests/Cache/TransformAsyncFixture.cs
@@ -26,7 +26,7 @@ public async Task Add()
 
         var firstPerson = await stub.TransformFactory(person);
 
-        stub.Results.Data.Items.First().Should().Be(firstPerson, "Should be same person");
+        stub.Results.Data.Items[0].Should().Be(firstPerson, "Should be same person");
     }
 
     [Fact]
@@ -183,7 +183,7 @@ public async Task SameKeyChanges()
         stub.Results.Data.Count.Should().Be(1, "Should result in 1 record");
 
         var lastTransformed = await stub.TransformFactory(people.Last());
-        var onlyItemInCache = stub.Results.Data.Items.First();
+        var onlyItemInCache = stub.Results.Data.Items[0];
 
         onlyItemInCache.Should().Be(lastTransformed, "Incorrect transform result");
     }
diff --git a/src/DynamicData.Tests/Cache/TransformFixture.cs b/src/DynamicData.Tests/Cache/TransformFixture.cs
index 89fa079b..d149276c 100644
--- a/src/DynamicData.Tests/Cache/TransformFixture.cs
+++ b/src/DynamicData.Tests/Cache/TransformFixture.cs
@@ -22,7 +22,7 @@ public void Add()
 
         stub.Results.Messages.Count.Should().Be(1, "Should be 1 updates");
         stub.Results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        stub.Results.Data.Items.First().Should().Be(stub.TransformFactory(person), "Should be same person");
+        stub.Results.Data.Items[0].Should().Be(stub.TransformFactory(person), "Should be same person");
     }
 
     [Fact]
@@ -130,7 +130,7 @@ public void SameKeyChanges()
         stub.Results.Data.Count.Should().Be(1, "Should result in 1 record");
 
         var lastTransformed = stub.TransformFactory(people.Last());
-        var onlyItemInCache = stub.Results.Data.Items.First();
+        var onlyItemInCache = stub.Results.Data.Items[0];
 
         onlyItemInCache.Should().Be(lastTransformed, "Incorrect transform result");
     }
diff --git a/src/DynamicData.Tests/Cache/TransformFixtureParallel.cs b/src/DynamicData.Tests/Cache/TransformFixtureParallel.cs
index 1f61a7d7..5ff66a0d 100644
--- a/src/DynamicData.Tests/Cache/TransformFixtureParallel.cs
+++ b/src/DynamicData.Tests/Cache/TransformFixtureParallel.cs
@@ -38,7 +38,7 @@ public void Add()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(_transformFactory(person), "Should be same person");
+        _results.Data.Items[0].Should().Be(_transformFactory(person), "Should be same person");
     }
 
     [Fact]
@@ -104,7 +104,7 @@ public void SameKeyChanges()
         _results.Data.Count.Should().Be(1, "Should result in 1 record");
 
         var lastTransformed = _transformFactory(people.Last());
-        var onlyItemInCache = _results.Data.Items.First();
+        var onlyItemInCache = _results.Data.Items[0];
 
         // TODO: This is not producing consitent results, the lastTransformed item should be equal to the onlyItemInCache
         onlyItemInCache.Should().Be(lastTransformed, "Incorrect transform result");
diff --git a/src/DynamicData.Tests/Cache/TransformManyAsyncFixture.cs b/src/DynamicData.Tests/Cache/TransformManyAsyncFixture.cs
index c426ef1f..3781b1a2 100644
--- a/src/DynamicData.Tests/Cache/TransformManyAsyncFixture.cs
+++ b/src/DynamicData.Tests/Cache/TransformManyAsyncFixture.cs
@@ -231,7 +231,7 @@ private static void CheckResultContents<T>(IEnumerable<AnimalOwner> owners, Chan
 
         // These should be subsets of each other
         expectedOwners.Should().BeSubsetOf(ownerResults.Data.Items);
-        ownerResults.Data.Items.Count().Should().Be(expectedOwners.Count);
+        ownerResults.Data.Items.Count.Should().Be(expectedOwners.Count);
 
         var allAnimals = expectedOwners.SelectMany(owner => owner.Animals.Items).ToList();
         var expectedAnimals = allAnimals.GroupBy(keySelector).Select(group => group.OrderBy(a => a, comparer).First()).ToList();
@@ -247,7 +247,7 @@ private static void CheckResultContents<T>(IEnumerable<AnimalOwner> owners, Chan
 
         // These should be subsets of each other
         expectedOwners.Should().BeSubsetOf(ownerResults.Data.Items);
-        ownerResults.Data.Items.Count().Should().Be(expectedOwners.Count);
+        ownerResults.Data.Items.Count.Should().Be(expectedOwners.Count);
 
         // All owner animals should be in the results
         foreach (var owner in owners)
diff --git a/src/DynamicData.Tests/Cache/TransformSafeAsyncFixture.cs b/src/DynamicData.Tests/Cache/TransformSafeAsyncFixture.cs
index 9221bd1b..6c1f34ef 100644
--- a/src/DynamicData.Tests/Cache/TransformSafeAsyncFixture.cs
+++ b/src/DynamicData.Tests/Cache/TransformSafeAsyncFixture.cs
@@ -72,7 +72,7 @@ public async Task Add()
 
         var firstPerson = await stub.TransformFactory(person);
 
-        stub.Results.Data.Items.First().Should().Be(firstPerson, "Should be same person");
+        stub.Results.Data.Items[0].Should().Be(firstPerson, "Should be same person");
     }
 
     [Fact]
@@ -139,7 +139,7 @@ public async Task SameKeyChanges()
         stub.Results.Data.Count.Should().Be(1, "Should result in 1 record");
 
         var lastTransformed = await stub.TransformFactory(people.Last());
-        var onlyItemInCache = stub.Results.Data.Items.First();
+        var onlyItemInCache = stub.Results.Data.Items[0];
 
         onlyItemInCache.Should().Be(lastTransformed, "Incorrect transform result");
     }
diff --git a/src/DynamicData.Tests/Cache/TransformSafeFixture.cs b/src/DynamicData.Tests/Cache/TransformSafeFixture.cs
index 1f31ec84..cd9aabc7 100644
--- a/src/DynamicData.Tests/Cache/TransformSafeFixture.cs
+++ b/src/DynamicData.Tests/Cache/TransformSafeFixture.cs
@@ -57,7 +57,7 @@ public void AddWithNoError()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(_transformFactory(person), "Should be same person");
+        _results.Data.Items[0].Should().Be(_transformFactory(person), "Should be same person");
     }
 
     public void Dispose()
@@ -86,7 +86,7 @@ public void UpdateBatch()
         _results.Messages.Count.Should().Be(1, "Should be 1 messages");
 
         _results.Data.Count.Should().Be(1, "Should 1 item in the cache");
-        _results.Data.Items.First().Should().Be(_transformFactory(update2), "Change 2 shoud be the only item cached");
+        _results.Data.Items[0].Should().Be(_transformFactory(update2), "Change 2 shoud be the only item cached");
     }
 
     [Fact]
@@ -121,6 +121,6 @@ public void UpdateSucessively()
         _results.Messages.Count.Should().Be(3, "Should be 3 messages");
 
         _results.Data.Count.Should().Be(1, "Should 1 item in the cache");
-        _results.Data.Items.First().Should().Be(_transformFactory(update2), "Change 2 shoud be the only item cached");
+        _results.Data.Items[0].Should().Be(_transformFactory(update2), "Change 2 shoud be the only item cached");
     }
 }
diff --git a/src/DynamicData.Tests/Cache/TransformSafeParallelFixture.cs b/src/DynamicData.Tests/Cache/TransformSafeParallelFixture.cs
index a344e09f..dace5e75 100644
--- a/src/DynamicData.Tests/Cache/TransformSafeParallelFixture.cs
+++ b/src/DynamicData.Tests/Cache/TransformSafeParallelFixture.cs
@@ -57,7 +57,7 @@ public void AddWithNoError()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().Should().Be(_transformFactory(person), "Should be same person");
+        _results.Data.Items[0].Should().Be(_transformFactory(person), "Should be same person");
     }
 
     public void Dispose()
@@ -86,7 +86,7 @@ public void UpdateBatch()
         _results.Messages.Count.Should().Be(1, "Should be 1 messages");
 
         _results.Data.Count.Should().Be(1, "Should 1 item in the cache");
-        _results.Data.Items.First().Should().Be(_transformFactory(update2), "Change 2 shoud be the only item cached");
+        _results.Data.Items[0].Should().Be(_transformFactory(update2), "Change 2 shoud be the only item cached");
     }
 
     [Fact]
@@ -121,6 +121,6 @@ public void UpdateSucessively()
         _results.Messages.Count.Should().Be(3, "Should be 3 messages");
 
         _results.Data.Count.Should().Be(1, "Should 1 item in the cache");
-        _results.Data.Items.First().Should().Be(_transformFactory(update2), "Change 2 shoud be the only item cached");
+        _results.Data.Items[0].Should().Be(_transformFactory(update2), "Change 2 shoud be the only item cached");
     }
 }
diff --git a/src/DynamicData.Tests/Cache/TransformTreeFixture.cs b/src/DynamicData.Tests/Cache/TransformTreeFixture.cs
index e24bb4fb..33bf4457 100644
--- a/src/DynamicData.Tests/Cache/TransformTreeFixture.cs
+++ b/src/DynamicData.Tests/Cache/TransformTreeFixture.cs
@@ -36,10 +36,10 @@ public void AddMissingChild()
 
         _result.Count.Should().Be(1);
 
-        var firstNode = _result.Items.First();
+        var firstNode = _result.Items[0];
         firstNode.Item.Should().Be(boss);
 
-        var childNode = firstNode.Children.Items.First();
+        var childNode = firstNode.Children.Items[0];
         childNode.Item.Should().Be(minion);
     }
 
@@ -81,7 +81,7 @@ public void BuildTreeFromMixedData()
         _sourceCache.AddOrUpdate(TransformTreeFixture.CreateEmployees());
         _result.Count.Should().Be(2);
 
-        var firstNode = _result.Items.First();
+        var firstNode = _result.Items[0];
         firstNode.Children.Count.Should().Be(3);
 
         var secondNode = _result.Items.Skip(1).First();
@@ -157,7 +157,7 @@ public void UpdateAParentNode()
         _sourceCache.AddOrUpdate(changed);
         _result.Count.Should().Be(2);
 
-        var firstNode = _result.Items.First();
+        var firstNode = _result.Items[0];
         firstNode.Children.Count.Should().Be(3);
         firstNode.Item.Name.Should().Be(changed.Name);
     }
@@ -176,7 +176,7 @@ public void UpdateChildNode()
         _sourceCache.AddOrUpdate(changed);
         _result.Count.Should().Be(2);
 
-        var changedNode = _result.Items.First().Children.Items.First();
+        var changedNode = _result.Items[0].Children.Items[0];
 
         changedNode.Parent.Value.Item.Id.Should().Be(1);
         changedNode.Children.Count.Should().Be(1);
diff --git a/src/DynamicData.Tests/Cache/TransformWithInlineUpdateFixture.cs b/src/DynamicData.Tests/Cache/TransformWithInlineUpdateFixture.cs
index 88249e34..0be034a1 100644
--- a/src/DynamicData.Tests/Cache/TransformWithInlineUpdateFixture.cs
+++ b/src/DynamicData.Tests/Cache/TransformWithInlineUpdateFixture.cs
@@ -17,17 +17,17 @@ public void InlineUpdate()
         var person = new Person("Adult1", 50);
         stub.Source.AddOrUpdate(person);
 
-        var transformedPerson = stub.Results.Data.Items.First();
+        var transformedPerson = stub.Results.Data.Items[0];
 
         var personUpdate = new Person("Adult1", 51);
         stub.Source.AddOrUpdate(personUpdate);
 
-        var updatedTransform = stub.Results.Data.Items.First();
+        var updatedTransform = stub.Results.Data.Items[0];
 
         updatedTransform.Age.Should().Be(personUpdate.Age, "Age should be updated from 50 to 51.");
         stub.Results.Messages.Count.Should().Be(2, "Should be 2 updates");
         stub.Results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        transformedPerson.Should().Be(stub.Results.Data.Items.First(), "Should be same transformed person instance.");
+        transformedPerson.Should().Be(stub.Results.Data.Items[0], "Should be same transformed person instance.");
     }
 
     [Fact]
@@ -84,17 +84,17 @@ public void TransformOnRefresh()
         var person = new Person("Adult1", 50);
         stub.Source.AddOrUpdate(person);
 
-        var transformedPerson = stub.Results.Data.Items.First();
+        var transformedPerson = stub.Results.Data.Items[0];
 
         person.Age = 51;
         stub.Source.Refresh(person);
 
-        var updatedTransform = stub.Results.Data.Items.First();
+        var updatedTransform = stub.Results.Data.Items[0];
 
         updatedTransform.Age.Should().Be(51, "Age should be updated from 50 to 51.");
         stub.Results.Messages.Count.Should().Be(2, "Should be 2 updates");
         stub.Results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        transformedPerson.Should().Be(stub.Results.Data.Items.First(), "Should be same transformed person instance.");
+        transformedPerson.Should().Be(stub.Results.Data.Items[0], "Should be same transformed person instance.");
     }
 
     private class TransformWithInlineUpdateFixtureStub : IDisposable
diff --git a/src/DynamicData.Tests/Cache/WatchFixture.cs b/src/DynamicData.Tests/Cache/WatchFixture.cs
index 9064cd28..6cc1116b 100644
--- a/src/DynamicData.Tests/Cache/WatchFixture.cs
+++ b/src/DynamicData.Tests/Cache/WatchFixture.cs
@@ -26,7 +26,7 @@ public void AddWillNotCallDispose()
 
         _results.Messages.Count.Should().Be(1, "Should be 1 updates");
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
-        _results.Data.Items.First().IsDisposed.Should().Be(false, "Should not be disposed");
+        _results.Data.Items[0].IsDisposed.Should().Be(false, "Should not be disposed");
     }
 
     public void Dispose()
diff --git a/src/DynamicData.Tests/Cache/WatcherFixture.cs b/src/DynamicData.Tests/Cache/WatcherFixture.cs
index 8fde8909..23faff11 100644
--- a/src/DynamicData.Tests/Cache/WatcherFixture.cs
+++ b/src/DynamicData.Tests/Cache/WatcherFixture.cs
@@ -57,7 +57,7 @@ public void AddNew()
         _results.Data.Count.Should().Be(1, "Should be 1 item in the cache");
 
         _scheduler.AdvanceBy(TimeSpan.FromMilliseconds(50).Ticks);
-        var result = _results.Data.Items.First();
+        var result = _results.Data.Items[0];
         result.UpdateCount.Should().Be(1, "Person should have received 1 update");
         result.Completed.Should().Be(false, "Person should have received 1 update");
     }
diff --git a/src/DynamicData.Tests/List/MergeManyChangeSetsCacheFixture.cs b/src/DynamicData.Tests/List/MergeManyChangeSetsCacheFixture.cs
index 547dd1eb..bdac643d 100644
--- a/src/DynamicData.Tests/List/MergeManyChangeSetsCacheFixture.cs
+++ b/src/DynamicData.Tests/List/MergeManyChangeSetsCacheFixture.cs
@@ -835,7 +835,7 @@ private void CheckResultContents(ChangeSetAggregator<IMarket> marketResults, Cha
 
         // These should be subsets of each other
         expectedPrices.Should().BeSubsetOf(priceResults.Data.Items);
-        priceResults.Data.Items.Count().Should().Be(expectedPrices.Count);
+        priceResults.Data.Items.Count.Should().Be(expectedPrices.Count);
     }
 
     private void DisposeMarkets()
diff --git a/src/DynamicData.Tests/Utilities/TestSourceCache.cs b/src/DynamicData.Tests/Utilities/TestSourceCache.cs
index f08be159..30fe327d 100644
--- a/src/DynamicData.Tests/Utilities/TestSourceCache.cs
+++ b/src/DynamicData.Tests/Utilities/TestSourceCache.cs
@@ -32,17 +32,17 @@ public int Count
     public IObservable<int> CountChanged
         => _countChanged;
 
-    public IEnumerable<TObject> Items
+    public IReadOnlyList<TObject> Items
         => _source.Items;
     
-    public IEnumerable<TKey> Keys
+    public IReadOnlyList<TKey> Keys
         => _source.Keys;
 
     public Func<TObject, TKey> KeySelector
         => _source.KeySelector;
 
-    public IEnumerable<KeyValuePair<TKey, TObject>> KeyValues
-        => KeyValues;
+    public IReadOnlyDictionary<TKey, TObject> KeyValues
+        => _source.KeyValues;
 
     public void Complete()
     {
diff --git a/src/DynamicData/Cache/ChangeAwareCache.cs b/src/DynamicData/Cache/ChangeAwareCache.cs
index 9dc98086..65fd131f 100644
--- a/src/DynamicData/Cache/ChangeAwareCache.cs
+++ b/src/DynamicData/Cache/ChangeAwareCache.cs
@@ -63,6 +63,8 @@ public ChangeAwareCache(Dictionary<TKey, TObject> data)
     /// <inheritdoc />
     public IEnumerable<KeyValuePair<TKey, TObject>> KeyValues => _data;
 
+    internal Dictionary<TKey, TObject> GetDictionary() => _data;
+
     /// <summary>
     /// Adds the item to the cache without checking whether there is an existing value in the cache.
     /// </summary>
diff --git a/src/DynamicData/Cache/IObservableCache.cs b/src/DynamicData/Cache/IObservableCache.cs
index 1ffb3e18..aaa73fcb 100644
--- a/src/DynamicData/Cache/IObservableCache.cs
+++ b/src/DynamicData/Cache/IObservableCache.cs
@@ -24,17 +24,17 @@ public interface IObservableCache<TObject, TKey> : IConnectableCache<TObject, TK
     /// <summary>
     /// Gets the Items.
     /// </summary>
-    IEnumerable<TObject> Items { get; }
+    IReadOnlyList<TObject> Items { get; }
 
     /// <summary>
     /// Gets the keys.
     /// </summary>
-    IEnumerable<TKey> Keys { get; }
+    IReadOnlyList<TKey> Keys { get; }
 
     /// <summary>
     /// Gets the key value pairs.
     /// </summary>
-    IEnumerable<KeyValuePair<TKey, TObject>> KeyValues { get; }
+    IReadOnlyDictionary<TKey, TObject> KeyValues { get; }
 
     /// <summary>
     /// Lookup a single item using the specified key.
diff --git a/src/DynamicData/Cache/IntermediateCache.cs b/src/DynamicData/Cache/IntermediateCache.cs
index 6125c9cd..3e77eff4 100644
--- a/src/DynamicData/Cache/IntermediateCache.cs
+++ b/src/DynamicData/Cache/IntermediateCache.cs
@@ -46,13 +46,13 @@ public IntermediateCache(IObservable<IChangeSet<TObject, TKey>> source)
     public IObservable<int> CountChanged => _innerCache.CountChanged;
 
     /// <inheritdoc />
-    public IEnumerable<TObject> Items => _innerCache.Items;
+    public IReadOnlyList<TObject> Items => _innerCache.Items;
 
     /// <inheritdoc />
-    public IEnumerable<TKey> Keys => _innerCache.Keys;
+    public IReadOnlyList<TKey> Keys => _innerCache.Keys;
 
     /// <inheritdoc />
-    public IEnumerable<KeyValuePair<TKey, TObject>> KeyValues => _innerCache.KeyValues;
+    public IReadOnlyDictionary<TKey, TObject> KeyValues => _innerCache.KeyValues;
 
     /// <inheritdoc />
     public IObservable<IChangeSet<TObject, TKey>> Connect(Func<TObject, bool>? predicate = null, bool suppressEmptyChangeSets = true)
diff --git a/src/DynamicData/Cache/Internal/AnonymousObservableCache.cs b/src/DynamicData/Cache/Internal/AnonymousObservableCache.cs
index 5f4e49fe..c7f52e59 100644
--- a/src/DynamicData/Cache/Internal/AnonymousObservableCache.cs
+++ b/src/DynamicData/Cache/Internal/AnonymousObservableCache.cs
@@ -37,11 +37,11 @@ public AnonymousObservableCache(IObservableCache<TObject, TKey> cache)
 
     public IObservable<int> CountChanged => _cache.CountChanged;
 
-    public IEnumerable<TObject> Items => _cache.Items;
+    public IReadOnlyList<TObject> Items => _cache.Items;
 
-    public IEnumerable<TKey> Keys => _cache.Keys;
+    public IReadOnlyList<TKey> Keys => _cache.Keys;
 
-    public IEnumerable<KeyValuePair<TKey, TObject>> KeyValues => _cache.KeyValues;
+    public IReadOnlyDictionary<TKey, TObject> KeyValues => _cache.KeyValues;
 
     public IObservable<IChangeSet<TObject, TKey>> Connect(Func<TObject, bool>? predicate = null, bool suppressEmptyChangeSets = true)
         => _cache.Connect(predicate, suppressEmptyChangeSets);
diff --git a/src/DynamicData/Cache/Internal/LockFreeObservableCache.cs b/src/DynamicData/Cache/Internal/LockFreeObservableCache.cs
index 6c468bb8..5e48a6b5 100644
--- a/src/DynamicData/Cache/Internal/LockFreeObservableCache.cs
+++ b/src/DynamicData/Cache/Internal/LockFreeObservableCache.cs
@@ -84,13 +84,13 @@ public LockFreeObservableCache()
     public IObservable<int> CountChanged => _countChanged.StartWith(_innerCache.Count).DistinctUntilChanged();
 
     /// <inheritdoc />
-    public IEnumerable<TObject> Items => _innerCache.Items;
+    public IReadOnlyList<TObject> Items => _innerCache.Items.ToArray();
 
     /// <inheritdoc />
-    public IEnumerable<TKey> Keys => _innerCache.Keys;
+    public IReadOnlyList<TKey> Keys => _innerCache.Keys.ToArray();
 
     /// <inheritdoc />
-    public IEnumerable<KeyValuePair<TKey, TObject>> KeyValues => _innerCache.KeyValues;
+    public IReadOnlyDictionary<TKey, TObject> KeyValues => new Dictionary<TKey, TObject>(_innerCache.GetDictionary());
 
     /// <inheritdoc />
     public IObservable<IChangeSet<TObject, TKey>> Connect(Func<TObject, bool>? predicate = null, bool suppressEmptyChangeSets = true) => Observable.Defer(
diff --git a/src/DynamicData/Cache/Internal/ReaderWriter.cs b/src/DynamicData/Cache/Internal/ReaderWriter.cs
index 2ce81f3b..f7a0debf 100644
--- a/src/DynamicData/Cache/Internal/ReaderWriter.cs
+++ b/src/DynamicData/Cache/Internal/ReaderWriter.cs
@@ -49,13 +49,13 @@ public TKey[] Keys
         }
     }
 
-    public KeyValuePair<TKey, TObject>[] KeyValues
+    public IReadOnlyDictionary<TKey, TObject> KeyValues
     {
         get
         {
             lock (_locker)
             {
-                return [.. _data];
+                return new Dictionary<TKey, TObject>(_data);
             }
         }
     }
diff --git a/src/DynamicData/Cache/ObservableCache.cs b/src/DynamicData/Cache/ObservableCache.cs
index dc09600b..0ef8fc1c 100644
--- a/src/DynamicData/Cache/ObservableCache.cs
+++ b/src/DynamicData/Cache/ObservableCache.cs
@@ -115,11 +115,11 @@ public ObservableCache(Func<TObject, TKey>? keySelector = null)
                 }
             });
 
-    public IEnumerable<TObject> Items => _readerWriter.Items;
+    public IReadOnlyList<TObject> Items => _readerWriter.Items;
 
-    public IEnumerable<TKey> Keys => _readerWriter.Keys;
+    public IReadOnlyList<TKey> Keys => _readerWriter.Keys;
 
-    public IEnumerable<KeyValuePair<TKey, TObject>> KeyValues => _readerWriter.KeyValues;
+    public IReadOnlyDictionary<TKey, TObject> KeyValues => _readerWriter.KeyValues;
 
     public IObservable<IChangeSet<TObject, TKey>> Connect(Func<TObject, bool>? predicate = null, bool suppressEmptyChangeSets = true) =>
         Observable.Create<IChangeSet<TObject, TKey>>(observer =>
diff --git a/src/DynamicData/Cache/SourceCache.cs b/src/DynamicData/Cache/SourceCache.cs
index 7959a0bf..8d720cba 100644
--- a/src/DynamicData/Cache/SourceCache.cs
+++ b/src/DynamicData/Cache/SourceCache.cs
@@ -34,16 +34,16 @@ public sealed class SourceCache<TObject, TKey>(Func<TObject, TKey> keySelector)
     public IObservable<int> CountChanged => _innerCache.CountChanged;
 
     /// <inheritdoc />
-    public IEnumerable<TObject> Items => _innerCache.Items;
+    public IReadOnlyList<TObject> Items => _innerCache.Items;
 
     /// <inheritdoc />
-    public IEnumerable<TKey> Keys => _innerCache.Keys;
+    public IReadOnlyList<TKey> Keys => _innerCache.Keys;
 
     /// <inheritdoc/>
     public Func<TObject, TKey> KeySelector { get; } = keySelector ?? throw new ArgumentNullException(nameof(keySelector));
 
     /// <inheritdoc />
-    public IEnumerable<KeyValuePair<TKey, TObject>> KeyValues => _innerCache.KeyValues;
+    public IReadOnlyDictionary<TKey, TObject> KeyValues => _innerCache.KeyValues;
 
     /// <inheritdoc />
     public IObservable<IChangeSet<TObject, TKey>> Connect(Func<TObject, bool>? predicate = null, bool suppressEmptyChangeSets = true) => _innerCache.Connect(predicate, suppressEmptyChangeSets);