Allow configuration of the sentinel value that indicates a property has not been set

src/EFCore.Design/Scaffolding/Internal/CSharpRuntimeModelCodeGenerator.cs

@@ -834,6 +834,14 @@ private void Create(
                 .Append("()");
         }
 
+        var sentinel = property.Sentinel;
+        if (sentinel != null)
+        {
+            mainBuilder.AppendLine(",")
+                .Append("sentinel: ")
+                .Append(_code.UnknownLiteral(sentinel));
+        }
+
         mainBuilder
             .AppendLine(");")
             .DecrementIndent();

src/EFCore/ChangeTracking/Internal/KeyPropagator.cs

@@ -149,9 +149,8 @@ private static void SetValue(InternalEntityEntry entry, IProperty property, Valu
 
                         if (principalProperty != property)
                         {
-                            var principalValue = principalEntry[principalProperty];
                             if (generationProperty == null
-                                || !principalProperty.ClrType.IsDefaultValue(principalValue))
+                                || principalEntry.HasExplicitValue(principalProperty))
                             {
                                 entry.PropagateValue(principalEntry, principalProperty, property);
 

src/EFCore/ChangeTracking/Internal/SidecarValues.cs

@@ -26,8 +26,11 @@ public bool TryGetValue(int index, out object? value)
             return true;
         }
 
+        public object? GetValue(int index)
+            => _values[index];
+
         public T GetValue<T>(int index)
-            => IsEmpty ? default! : _values.GetValue<T>(index);
+            => _values.GetValue<T>(index);
 
         public void SetValue(IProperty property, object? value, int index)
         {

src/EFCore/ChangeTracking/Internal/SimpleFullyNullableDependentKeyValueFactory.cs

@@ -61,7 +61,7 @@ public virtual bool TryCreateFromBuffer(in ValueBuffer valueBuffer, [NotNullWhen
     /// </summary>
     public override bool TryCreateFromCurrentValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = ((Func<IUpdateEntry, TKey>)_propertyAccessors.CurrentValueGetter)(entry);
+        key = ((Func<InternalEntityEntry, TKey>)_propertyAccessors.CurrentValueGetter)((InternalEntityEntry)entry);
         return key != null;
     }
 
@@ -73,7 +73,7 @@ public override bool TryCreateFromCurrentValues(IUpdateEntry entry, [NotNullWhen
     /// </summary>
     public virtual bool TryCreateFromPreStoreGeneratedCurrentValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = ((Func<IUpdateEntry, TKey>)_propertyAccessors.PreStoreGeneratedCurrentValueGetter)(entry);
+        key = ((Func<InternalEntityEntry, TKey>)_propertyAccessors.PreStoreGeneratedCurrentValueGetter)((InternalEntityEntry)entry);
         return key != null;
     }
 
@@ -85,7 +85,7 @@ public virtual bool TryCreateFromPreStoreGeneratedCurrentValues(IUpdateEntry ent
     /// </summary>
     public override bool TryCreateFromOriginalValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = ((Func<IUpdateEntry, TKey>)_propertyAccessors.OriginalValueGetter!)(entry);
+        key = ((Func<InternalEntityEntry, TKey>)_propertyAccessors.OriginalValueGetter!)((InternalEntityEntry)entry);
         return key != null;
     }
 
@@ -97,7 +97,7 @@ public override bool TryCreateFromOriginalValues(IUpdateEntry entry, [NotNullWhe
     /// </summary>
     public virtual bool TryCreateFromRelationshipSnapshot(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = ((Func<IUpdateEntry, TKey>)_propertyAccessors.RelationshipSnapshotGetter)(entry);
+        key = ((Func<InternalEntityEntry, TKey>)_propertyAccessors.RelationshipSnapshotGetter)((InternalEntityEntry)entry);
         return key != null;
     }
 }

src/EFCore/ChangeTracking/Internal/SimpleNonNullableDependentKeyValueFactory.cs

@@ -68,7 +68,7 @@ public virtual bool TryCreateFromBuffer(in ValueBuffer valueBuffer, [NotNullWhen
     /// </summary>
     public override bool TryCreateFromCurrentValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = ((Func<IUpdateEntry, TKey>)_propertyAccessors.CurrentValueGetter)(entry)!;
+        key = ((Func<InternalEntityEntry, TKey>)_propertyAccessors.CurrentValueGetter)((InternalEntityEntry)entry)!;
         return true;
     }
 
@@ -80,7 +80,7 @@ public override bool TryCreateFromCurrentValues(IUpdateEntry entry, [NotNullWhen
     /// </summary>
     public virtual bool TryCreateFromPreStoreGeneratedCurrentValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = ((Func<IUpdateEntry, TKey>)_propertyAccessors.PreStoreGeneratedCurrentValueGetter)(entry)!;
+        key = ((Func<InternalEntityEntry, TKey>)_propertyAccessors.PreStoreGeneratedCurrentValueGetter)((InternalEntityEntry)entry)!;
         return true;
     }
 
@@ -92,7 +92,7 @@ public virtual bool TryCreateFromPreStoreGeneratedCurrentValues(IUpdateEntry ent
     /// </summary>
     public override bool TryCreateFromOriginalValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = ((Func<IUpdateEntry, TKey>)_propertyAccessors.OriginalValueGetter!)(entry)!;
+        key = ((Func<InternalEntityEntry, TKey>)_propertyAccessors.OriginalValueGetter!)((InternalEntityEntry)entry)!;
         return true;
     }
 
@@ -104,7 +104,7 @@ public override bool TryCreateFromOriginalValues(IUpdateEntry entry, [NotNullWhe
     /// </summary>
     public virtual bool TryCreateFromRelationshipSnapshot(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = ((Func<IUpdateEntry, TKey>)_propertyAccessors.RelationshipSnapshotGetter)(entry)!;
+        key = ((Func<InternalEntityEntry, TKey>)_propertyAccessors.RelationshipSnapshotGetter)((InternalEntityEntry)entry)!;
         return true;
     }
 }

src/EFCore/ChangeTracking/Internal/SimpleNullableDependentKeyValueFactory.cs

@@ -66,7 +66,7 @@ public virtual bool TryCreateFromBuffer(in ValueBuffer valueBuffer, out TKey key
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     public override bool TryCreateFromCurrentValues(IUpdateEntry entry, out TKey key)
-        => HandleNullableValue(((Func<IUpdateEntry, TKey?>)_propertyAccessors.CurrentValueGetter)(entry), out key);
+        => HandleNullableValue(((Func<InternalEntityEntry, TKey?>)_propertyAccessors.CurrentValueGetter)((InternalEntityEntry)entry), out key);
 
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -76,7 +76,7 @@ public override bool TryCreateFromCurrentValues(IUpdateEntry entry, out TKey key
     /// </summary>
     public virtual bool TryCreateFromPreStoreGeneratedCurrentValues(IUpdateEntry entry, out TKey key)
         => HandleNullableValue(
-            ((Func<IUpdateEntry, TKey?>)_propertyAccessors.PreStoreGeneratedCurrentValueGetter)(entry), out key);
+            ((Func<InternalEntityEntry, TKey?>)_propertyAccessors.PreStoreGeneratedCurrentValueGetter)((InternalEntityEntry)entry), out key);
 
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -85,7 +85,7 @@ public virtual bool TryCreateFromPreStoreGeneratedCurrentValues(IUpdateEntry ent
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     public override bool TryCreateFromOriginalValues(IUpdateEntry entry, out TKey key)
-        => HandleNullableValue(((Func<IUpdateEntry, TKey?>)_propertyAccessors.OriginalValueGetter!)(entry), out key);
+        => HandleNullableValue(((Func<InternalEntityEntry, TKey?>)_propertyAccessors.OriginalValueGetter!)((InternalEntityEntry)entry), out key);
 
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -94,7 +94,7 @@ public override bool TryCreateFromOriginalValues(IUpdateEntry entry, out TKey ke
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     public virtual bool TryCreateFromRelationshipSnapshot(IUpdateEntry entry, out TKey key)
-        => HandleNullableValue(((Func<IUpdateEntry, TKey?>)_propertyAccessors.RelationshipSnapshotGetter)(entry), out key);
+        => HandleNullableValue(((Func<InternalEntityEntry, TKey?>)_propertyAccessors.RelationshipSnapshotGetter)((InternalEntityEntry)entry), out key);
 
     private static bool HandleNullableValue(TKey? value, out TKey key)
     {

src/EFCore/ChangeTracking/Internal/SimpleNullablePrincipalDependentKeyValueFactory.cs

@@ -72,7 +72,7 @@ public virtual bool TryCreateFromBuffer(in ValueBuffer valueBuffer, [NotNullWhen
     /// </summary>
     public override bool TryCreateFromCurrentValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = (TKey)(object)((Func<IUpdateEntry, TNonNullableKey>)_propertyAccessors.CurrentValueGetter)(entry)!;
+        key = (TKey)(object)((Func<InternalEntityEntry, TNonNullableKey>)_propertyAccessors.CurrentValueGetter)((InternalEntityEntry)entry)!;
         return true;
     }
 
@@ -84,7 +84,7 @@ public override bool TryCreateFromCurrentValues(IUpdateEntry entry, [NotNullWhen
     /// </summary>
     public virtual bool TryCreateFromPreStoreGeneratedCurrentValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = (TKey)(object)((Func<IUpdateEntry, TNonNullableKey>)_propertyAccessors.PreStoreGeneratedCurrentValueGetter)(entry)!;
+        key = (TKey)(object)((Func<InternalEntityEntry, TNonNullableKey>)_propertyAccessors.PreStoreGeneratedCurrentValueGetter)((InternalEntityEntry)entry)!;
         return true;
     }
 
@@ -96,7 +96,7 @@ public virtual bool TryCreateFromPreStoreGeneratedCurrentValues(IUpdateEntry ent
     /// </summary>
     public override bool TryCreateFromOriginalValues(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = (TKey)(object)((Func<IUpdateEntry, TNonNullableKey>)_propertyAccessors.OriginalValueGetter!)(entry)!;
+        key = (TKey)(object)((Func<InternalEntityEntry, TNonNullableKey>)_propertyAccessors.OriginalValueGetter!)((InternalEntityEntry)entry)!;
         return true;
     }
 
@@ -108,7 +108,7 @@ public override bool TryCreateFromOriginalValues(IUpdateEntry entry, [NotNullWhe
     /// </summary>
     public virtual bool TryCreateFromRelationshipSnapshot(IUpdateEntry entry, [NotNullWhen(true)] out TKey? key)
     {
-        key = (TKey)(object)((Func<IUpdateEntry, TNonNullableKey>)_propertyAccessors.RelationshipSnapshotGetter)(entry)!;
+        key = (TKey)(object)((Func<InternalEntityEntry, TNonNullableKey>)_propertyAccessors.RelationshipSnapshotGetter)((InternalEntityEntry)entry)!;
         return true;
     }
 }

src/EFCore/ChangeTracking/Internal/SimplePrincipalKeyValueFactory.cs

@@ -68,7 +68,7 @@ public virtual IProperty FindNullPropertyInKeyValues(IReadOnlyList<object?> keyV
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     public virtual TKey CreateFromCurrentValues(IUpdateEntry entry)
-        => ((Func<IUpdateEntry, TKey>)_propertyAccessors.CurrentValueGetter)(entry);
+        => ((Func<InternalEntityEntry, TKey>)_propertyAccessors.CurrentValueGetter)((InternalEntityEntry)entry);
 
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -86,7 +86,7 @@ public virtual IProperty FindNullPropertyInCurrentValues(IUpdateEntry entry)
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     public virtual TKey CreateFromOriginalValues(IUpdateEntry entry)
-        => ((Func<IUpdateEntry, TKey>)_propertyAccessors.OriginalValueGetter!)(entry);
+        => ((Func<InternalEntityEntry, TKey>)_propertyAccessors.OriginalValueGetter!)((InternalEntityEntry)entry);
 
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -95,7 +95,7 @@ public virtual TKey CreateFromOriginalValues(IUpdateEntry entry)
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     public virtual TKey CreateFromRelationshipSnapshot(IUpdateEntry entry)
-        => ((Func<IUpdateEntry, TKey>)_propertyAccessors.RelationshipSnapshotGetter)(entry);
+        => ((Func<InternalEntityEntry, TKey>)_propertyAccessors.RelationshipSnapshotGetter)((InternalEntityEntry)entry);
 
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -119,18 +119,6 @@ public virtual object CreateEquatableKey(IUpdateEntry entry, bool fromOriginalVa
                 : CreateFromCurrentValues(entry),
             EqualityComparer);
 
-    private sealed class NoNullsStructuralEqualityComparer : IEqualityComparer<TKey>
-    {
-        private readonly IEqualityComparer _comparer
-            = StructuralComparisons.StructuralEqualityComparer;
-
-        public bool Equals(TKey? x, TKey? y)
-            => _comparer.Equals(x, y);
-
-        public int GetHashCode([DisallowNull] TKey obj)
-            => _comparer.GetHashCode(obj);
-    }
-
     private sealed class NoNullsCustomEqualityComparer : IEqualityComparer<TKey>
     {
         private readonly Func<TKey?, TKey?, bool> _equals;

src/EFCore/ChangeTracking/Internal/SnapshotFactoryFactory.cs

@@ -130,7 +130,7 @@ protected virtual Expression CreateSnapshotExpression(
 
             if (memberAccess.Type != propertyBase.ClrType)
             {
-                var hasDefaultValueExpression = memberAccess.MakeHasDefaultValue(propertyBase);
+                var hasDefaultValueExpression = memberAccess.MakeHasSentinelValue(propertyBase);
 
                 memberAccess = Expression.Condition(
                     hasDefaultValueExpression,

src/EFCore/ChangeTracking/Internal/StateData.cs

@@ -11,7 +11,8 @@ internal enum PropertyFlag
         Null = 1,
         Unknown = 2,
         IsLoaded = 3,
-        IsTemporary = 4
+        IsTemporary = 4,
+        IsStoreGenerated = 5
     }
 
     internal readonly struct StateData

src/EFCore/ChangeTracking/Internal/StateManager.cs

@@ -281,13 +281,13 @@ public virtual InternalEntityEntry CreateEntry(IDictionary<string, object?> valu
         {
             valuesArray[i++] = values.TryGetValue(property.Name, out var value)
                 ? value
-                : property.ClrType.GetDefaultValue();
+                : property.Sentinel;
 
             if (property.IsShadowProperty())
             {
                 shadowPropertyValuesArray[property.GetShadowIndex()] = values.TryGetValue(property.Name, out var shadowValue)
                     ? shadowValue
-                    : property.ClrType.GetDefaultValue();
+                    : property.Sentinel;
             }
         }
 

src/EFCore/ChangeTracking/Internal/ValueGenerationManager.cs

@@ -45,7 +45,8 @@ public ValueGenerationManager(
         InternalEntityEntry? chosenPrincipal = null;
         foreach (var property in entry.EntityType.GetForeignKeyProperties())
         {
-            if (!entry.HasDefaultValue(property))
+            if (!entry.IsUnknown(property)
+                && entry.HasExplicitValue(property))
             {
                 continue;
             }
@@ -68,7 +69,7 @@ public ValueGenerationManager(
         InternalEntityEntry? chosenPrincipal = null;
         foreach (var property in entry.EntityType.GetForeignKeyProperties())
         {
-            if (!entry.HasDefaultValue(property))
+            if (entry.HasExplicitValue(property))
             {
                 continue;
             }
@@ -94,7 +95,7 @@ public virtual bool Generate(InternalEntityEntry entry, bool includePrimaryKey =
 
         foreach (var property in entry.EntityType.GetValueGeneratingProperties())
         {
-            if (!entry.HasDefaultValue(property)
+            if (entry.HasExplicitValue(property)
                 || (!includePrimaryKey
                     && property.IsPrimaryKey()))
             {
@@ -153,7 +154,7 @@ public virtual async Task<bool> GenerateAsync(
         var hasNonStableValues = false;
         foreach (var property in entry.EntityType.GetValueGeneratingProperties())
         {
-            if (!entry.HasDefaultValue(property)
+            if (entry.HasExplicitValue(property)
                 || (!includePrimaryKey
                     && property.IsPrimaryKey()))
             {

src/EFCore/Extensions/Internal/ExpressionExtensions.cs

@@ -20,37 +20,55 @@ public static class ExpressionExtensions
     ///     any release. You should only use it directly in your code with extreme caution and knowing that
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
-    public static Expression MakeHasDefaultValue(
+    public static Expression MakeHasSentinelValue(
         this Expression currentValueExpression,
         IReadOnlyPropertyBase? propertyBase)
     {
-        if (!currentValueExpression.Type.IsValueType)
-        {
-            return Expression.ReferenceEqual(
-                currentValueExpression,
-                Expression.Constant(null, currentValueExpression.Type));
-        }
+        var sentinel = propertyBase?.Sentinel;
 
-        if (currentValueExpression.Type.IsGenericType
-            && currentValueExpression.Type.GetGenericTypeDefinition() == typeof(Nullable<>))
+        var isReferenceType = !currentValueExpression.Type.IsValueType;
+        var isNullableValueType = currentValueExpression.Type.IsGenericType
+            && currentValueExpression.Type.GetGenericTypeDefinition() == typeof(Nullable<>);
+
+        if (sentinel == null)
         {
-            return Expression.Not(
-                Expression.Call(
+            return isReferenceType
+                ? Expression.ReferenceEqual(
                     currentValueExpression,
-                    Check.NotNull(
-                        currentValueExpression.Type.GetMethod("get_HasValue"), $"get_HasValue on {currentValueExpression.Type.Name}")));
+                    Expression.Constant(null, currentValueExpression.Type))
+                : isNullableValueType
+                    ? Expression.Not(
+                        Expression.Call(
+                            currentValueExpression,
+                            currentValueExpression.Type.GetMethod("get_HasValue")!))
+                    : Expression.Constant(false);
         }
 
-        var property = propertyBase as IReadOnlyProperty;
-        var comparer = property?.GetValueComparer()
+        var comparer = (propertyBase as IProperty)?.GetValueComparer()
             ?? ValueComparer.CreateDefault(
                 propertyBase?.ClrType ?? currentValueExpression.Type, favorStructuralComparisons: false);
 
-        return comparer.ExtractEqualsBody(
+        var equalsExpression = comparer.ExtractEqualsBody(
             comparer.Type != currentValueExpression.Type
                 ? Expression.Convert(currentValueExpression, comparer.Type)
                 : currentValueExpression,
-            Expression.Default(comparer.Type));
+            Expression.Constant(sentinel, comparer.Type));
+
+        if (isReferenceType || isNullableValueType)
+        {
+            return Expression.AndAlso(
+                isReferenceType
+                    ? Expression.Not(
+                        Expression.ReferenceEqual(
+                            currentValueExpression,
+                            Expression.Constant(null, currentValueExpression.Type)))
+                    : Expression.Call(
+                        currentValueExpression,
+                        currentValueExpression.Type.GetMethod("get_HasValue")!),
+                equalsExpression);
+        }
+
+        return equalsExpression;
     }
 
     /// <summary>

src/EFCore/Metadata/Conventions/RuntimeModelConvention.cs

@@ -337,6 +337,7 @@ private static RuntimeProperty Create(IProperty property, RuntimeEntityType runt
         => runtimeEntityType.AddProperty(
             property.Name,
             property.ClrType,
+            property.Sentinel,
             property.PropertyInfo,
             property.FieldInfo,
             property.GetPropertyAccessMode(),

src/EFCore/Metadata/IClrPropertyGetter.cs

@@ -31,5 +31,5 @@ public interface IClrPropertyGetter
     /// </summary>
     /// <param name="entity">The entity instance.</param>
     /// <returns><see langword="true" /> if the property value is the CLR default; <see langword="false" /> it is any other value.</returns>
-    bool HasDefaultValue(object entity);
+    bool HasSentinelValue(object entity);
 }