Query: Use GetDiscriminatorValue for TPT and TPC

Add model validation when values are not unique
Resolves #28054

src/EFCore.Relational/Infrastructure/RelationalModelValidator.cs

@@ -1391,6 +1391,24 @@ protected override void ValidateInheritanceMapping(
 
                 ValidateNonTphMapping(entityType, forTables: false);
                 ValidateNonTphMapping(entityType, forTables: true);
+
+                var derivedTypes = entityType.GetDerivedTypesInclusive().ToList();
+                var discriminatorValues = new Dictionary<object, IEntityType>();
+                foreach (var derivedType in derivedTypes)
+                {
+                    if (!derivedType.ClrType.IsInstantiable())
+                    {
+                        continue;
+                    }
+                    var discriminatorValue = derivedType.ShortName();
+
+                    if (discriminatorValues.TryGetValue(discriminatorValue, out var duplicateEntityType))
+                    {
+                        throw new InvalidOperationException("TBD");
+                    }
+
+                    discriminatorValues[discriminatorValue] = derivedType;
+                }
             }
         }
 
@@ -1469,7 +1487,7 @@ private static void ValidateNonTphMapping(IEntityType rootEntityType, bool forTa
         {
             return;
         }
-        
+
         var internalForeignKey = rootEntityType.FindRowInternalForeignKeys(storeObject.Value).FirstOrDefault();
         if (internalForeignKey != null
             && derivedTypes.Count > 1

src/EFCore.Relational/Metadata/Internal/RelationalEntityTypeExtensions.cs

@@ -31,15 +31,6 @@ public static IEnumerable<ITableMappingBase> GetViewOrTableMappings(this IEntity
                 ?? entityType.FindRuntimeAnnotationValue(RelationalAnnotationNames.TableMappings))
             ?? Enumerable.Empty<ITableMappingBase>();
 
-    /// <summary>
-    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
-    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
-    ///     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 IReadOnlyList<string> GetTptDiscriminatorValues(this IReadOnlyEntityType entityType)
-        => entityType.GetConcreteDerivedTypesInclusive().Select(et => et.ShortName()).ToList();
-
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
     ///     the same compatibility standards as public APIs. It may be changed or removed without notice in

src/EFCore.Relational/Query/EntityProjectionExpression.cs

@@ -123,7 +123,7 @@ public virtual EntityProjectionExpression UpdateEntityType(IEntityType derivedTy
         var discriminatorExpression = DiscriminatorExpression;
         if (DiscriminatorExpression is CaseExpression caseExpression)
         {
-            var entityTypesToSelect = derivedType.GetTptDiscriminatorValues();
+            var entityTypesToSelect = derivedType.GetConcreteDerivedTypesInclusive().Select(e => e.GetDiscriminatorValue()).ToList();
             var whenClauses = caseExpression.WhenClauses
                 .Where(wc => entityTypesToSelect.Contains((string)((SqlConstantExpression)wc.Result).Value!))
                 .ToList();

src/EFCore.Relational/Query/RelationalSqlTranslatingExpressionVisitor.cs

@@ -1066,7 +1066,7 @@ protected override Expression VisitTypeBinary(TypeBinaryExpression typeBinaryExp
                     }
 
                     // TPT or TPC
-                    var discriminatorValues = derivedType.GetTptDiscriminatorValues();
+                    var discriminatorValues = derivedType.GetConcreteDerivedTypesInclusive().Select(e => e.GetDiscriminatorValue()).ToList();
                     if (entityReferenceExpression.SubqueryEntity != null)
                     {
                         var entityShaper = (EntityShaperExpression)entityReferenceExpression.SubqueryEntity.ShaperExpression;

src/EFCore/Metadata/IReadOnlyEntityType.cs

@@ -70,7 +70,8 @@ bool GetIsDiscriminatorMappingComplete()
     /// </summary>
     /// <returns>The discriminator value for this entity type.</returns>
     object? GetDiscriminatorValue()
-        => this[CoreAnnotationNames.DiscriminatorValue];
+        => this[CoreAnnotationNames.DiscriminatorValue]
+            ?? (GetDiscriminatorPropertyName() == null ? (object)ShortName() : null);
 
     /// <summary>
     ///     Gets all types in the model from which a given entity type derives, starting with the root.

test/EFCore.Relational.Tests/Infrastructure/RelationalModelValidatorTest.cs

@@ -485,9 +485,9 @@ public virtual void Passes_for_incompatible_uniquified_check_constraints_with_sh
         var modelBuilder = CreateConventionalModelBuilder();
 
         modelBuilder.Entity<A>().HasOne<B>().WithOne(b => b.A).HasForeignKey<A>(a => a.Id).HasPrincipalKey<B>(b => b.Id).IsRequired();
-            modelBuilder.Entity<A>().HasCheckConstraint("CK_Table_SomeCK", "Id > 0");
+        modelBuilder.Entity<A>().HasCheckConstraint("CK_Table_SomeCK", "Id > 0");
         modelBuilder.Entity<A>().ToTable("Table");
-            modelBuilder.Entity<B>().HasCheckConstraint("CK_Table_SomeCK", "Id > 10");
+        modelBuilder.Entity<B>().HasCheckConstraint("CK_Table_SomeCK", "Id > 10");
         modelBuilder.Entity<B>().ToTable("Table");
 
         var model = Validate(modelBuilder);
@@ -502,9 +502,9 @@ public virtual void Passes_for_compatible_shared_check_constraints_with_shared_t
         var modelBuilder = CreateConventionalModelBuilder();
 
         modelBuilder.Entity<A>().HasOne<B>().WithOne(b => b.A).HasForeignKey<A>(a => a.Id).HasPrincipalKey<B>(b => b.Id).IsRequired();
-            modelBuilder.Entity<A>().HasCheckConstraint("CK_Table_SomeCK", "Id > 0");
+        modelBuilder.Entity<A>().HasCheckConstraint("CK_Table_SomeCK", "Id > 0");
         modelBuilder.Entity<A>().ToTable("Table");
-            modelBuilder.Entity<B>().HasCheckConstraint("CK_Table_SomeCK", "Id > 0");
+        modelBuilder.Entity<B>().HasCheckConstraint("CK_Table_SomeCK", "Id > 0");
         modelBuilder.Entity<B>().ToTable("Table");
 
         var model = Validate(modelBuilder);
@@ -1853,7 +1853,7 @@ public virtual void Detects_clashing_entity_types_in_views_TPC()
         modelBuilder.Entity<Animal>().UseTpcMappingStrategy();
         modelBuilder.Entity<Cat>().ToTable("Cat").ToView("Cat");
         modelBuilder.Entity<Dog>().ToTable("Dog").ToView("Cat");
-        
+
         VerifyError(
             RelationalStrings.NonTphViewClash(nameof(Dog), nameof(Cat), "Cat"),
             modelBuilder);
@@ -1945,7 +1945,7 @@ public virtual void Passes_on_valid_view_sharing_with_TPC()
 
         Validate(modelBuilder);
     }
-    
+
     [ConditionalFact]
     public virtual void Detects_view_sharing_on_base_with_TPC()
     {
@@ -2511,6 +2511,38 @@ public virtual void Detects_triggers_on_unmapped_entity_types()
         VerifyError(RelationalStrings.TriggerOnUnmappedEntityType("Animal_Trigger", "Animal"), modelBuilder);
     }
 
+    [ConditionalFact]
+    public virtual void Throws_when_non_tph_entity_type_short_names_are_not_unique()
+    {
+        var modelBuilder = CreateConventionalModelBuilder();
+        modelBuilder.Entity<TpcBase>().UseTpcMappingStrategy();
+        modelBuilder.Entity<Outer.TpcDerived>().ToTable("TpcDerived1");
+        modelBuilder.Entity<Outer2.TpcDerived>().ToTable("TpcDerived2");
+
+        VerifyError("TBD", modelBuilder);
+    }
+
+    private class TpcBase
+    {
+        public int Id { get; set; }
+    }
+
+    private class Outer
+    {
+        public class TpcDerived : TpcBase
+        {
+            public string Value { get; set; }
+        }
+    }
+
+    private class Outer2
+    {
+        public class TpcDerived : TpcBase
+        {
+            public string Value { get; set; }
+        }
+    }
+
     protected override void SetBaseType(IMutableEntityType entityType, IMutableEntityType baseEntityType)
     {
         base.SetBaseType(entityType, baseEntityType);