Fix for object collections

Author: ajcvickers

src/EFCore.Relational/Storage/RelationalTypeMappingSource.cs

@@ -235,14 +235,12 @@ protected override CoreTypeMapping FindMapping(in TypeMappingInfo mappingInfo)
                         new ValueConverterInfo(modelType, typeof(string), _ => null!)))!
                 .Clone(
                     (ValueConverter)Activator.CreateInstance(
-                        typeof(CollectionToJsonStringConverter<>).MakeGenericType(
-                            elementType),
-                        collectionReaderWriter!)!,
+                        typeof(CollectionToJsonStringConverter<>).MakeGenericType(elementType), collectionReaderWriter!)!,
                     (ValueComparer?)Activator.CreateInstance(
                         elementType.IsNullableValueType()
                             ? typeof(NullableValueTypeListComparer<>).MakeGenericType(elementType.UnwrapNullableType())
-                            : typeof(ListComparer<>).MakeGenericType(elementType),
-                        elementMapping?.Comparer),
+                            : typeof(ListComparer<>).MakeGenericType(elementMapping!.Comparer.Type),
+                        elementMapping!.Comparer),
                     elementMapping,
                     collectionReaderWriter)
             : null;

src/EFCore/ChangeTracking/ListComparer.cs

@@ -112,7 +112,7 @@ private static IList<TElement> Snapshot(IEnumerable<TElement> source, ValueCompa
                     typeof(IList<>).MakeGenericType(elementComparer.Type).ShortDisplayName()));
         }
 
-        if (sourceList.GetType().IsArray)
+        if (sourceList.IsReadOnly)
         {
             var snapshot = new TElement[sourceList.Count];
 
@@ -129,7 +129,7 @@ private static IList<TElement> Snapshot(IEnumerable<TElement> source, ValueCompa
         }
         else
         {
-            var snapshot = source is List<TElement>
+            var snapshot = (source is List<TElement> || sourceList.IsReadOnly)
                 ? new List<TElement>(sourceList.Count)
                 : (IList<TElement>)Activator.CreateInstance(source.GetType())!;
 

src/EFCore/ChangeTracking/NullableValueTypeListComparer.cs

@@ -87,7 +87,7 @@ private static bool Compare(IEnumerable<TElement?>? a, IEnumerable<TElement?>? b
             CoreStrings.BadListType(
                 (a is IList<TElement?> ? b : a).GetType().ShortDisplayName(),
                 typeof(NullableValueTypeListComparer<TElement>).ShortDisplayName(),
-                typeof(IList<>).MakeGenericType(elementComparer.Type).ShortDisplayName()));
+                typeof(IList<>).MakeGenericType(elementComparer.Type.MakeNullable()).ShortDisplayName()));
     }
 
     private static int GetHashCode(IEnumerable<TElement?> source, ValueComparer<TElement> elementComparer)
@@ -110,10 +110,10 @@ private static int GetHashCode(IEnumerable<TElement?> source, ValueComparer<TEle
                 CoreStrings.BadListType(
                     source.GetType().ShortDisplayName(),
                     typeof(NullableValueTypeListComparer<TElement>).ShortDisplayName(),
-                    typeof(IList<>).MakeGenericType(elementComparer.Type).ShortDisplayName()));
+                    typeof(IList<>).MakeGenericType(elementComparer.Type.MakeNullable()).ShortDisplayName()));
         }
 
-        if (sourceList.GetType().IsArray)
+        if (sourceList.IsReadOnly)
         {
             var snapshot = new TElement?[sourceList.Count];
 
@@ -127,7 +127,7 @@ private static int GetHashCode(IEnumerable<TElement?> source, ValueComparer<TEle
         }
         else
         {
-            var snapshot = source is List<TElement?>
+            var snapshot = source is List<TElement?> || sourceList.IsReadOnly
                 ? new List<TElement?>(sourceList.Count)
                 : (IList<TElement?>)Activator.CreateInstance(source.GetType())!;
 

src/EFCore/Storage/TypeMappingSource.cs

@@ -191,14 +191,12 @@ protected TypeMappingSource(TypeMappingSourceDependencies dependencies)
                         new ValueConverterInfo(modelType, typeof(string), _ => null!)))!
                 .Clone(
                     (ValueConverter)Activator.CreateInstance(
-                        typeof(CollectionToJsonStringConverter<>).MakeGenericType(
-                            elementType!),
-                        collectionReaderWriter!)!,
+                        typeof(CollectionToJsonStringConverter<>).MakeGenericType(elementType), collectionReaderWriter!)!,
                     (ValueComparer?)Activator.CreateInstance(
                         elementType.IsNullableValueType()
                             ? typeof(NullableValueTypeListComparer<>).MakeGenericType(elementType.UnwrapNullableType())
-                            : typeof(ListComparer<>).MakeGenericType(elementType),
-                        elementMapping?.Comparer),
+                            : typeof(ListComparer<>).MakeGenericType(elementMapping!.Comparer.Type),
+                        elementMapping!.Comparer),
                     elementMapping,
                     collectionReaderWriter)
             : null;