Fix NullReferenceException when accessing null complex properties in TPH with shared columns

src/EFCore/Metadata/Internal/PropertyAccessorsFactory.cs

@@ -302,8 +302,18 @@ public static Expression CreateMemberAccess(
                     break;
             }
         }
-        else
+        else if (!fromDeclaringType
+                 || !addNullCheck
+                 || property is not IComplexProperty complexProperty
+                 || instanceExpression.Type.IsValueType
+                 || complexProperty.ClrType.IsValueType)
         {
+            // Disable null check for all cases except:
+            // - fromDeclaringType is true AND
+            // - addNullCheck is true AND  
+            // - property is a complex property AND
+            // - instance is a reference type AND
+            // - complex property type is a reference type
             addNullCheck = false;
         }
 

test/EFCore.SqlServer.FunctionalTests/TPHComplexPropertySharingTest.cs

@@ -0,0 +1,136 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.EntityFrameworkCore;
+
+public class TPHComplexPropertySharingTest(TPHComplexPropertySharingTest.TPHComplexPropertySharingFixture fixture)
+    : IClassFixture<TPHComplexPropertySharingTest.TPHComplexPropertySharingFixture>
+{
+    protected TPHComplexPropertySharingFixture Fixture { get; } = fixture;
+
+    [ConditionalFact]
+    public virtual async Task Can_save_and_query_TPH_with_shared_complex_property_column()
+    {
+        await using var context = CreateContext();
+        await context.Database.EnsureDeletedAsync();
+        await context.Database.EnsureCreatedAsync();
+
+        context.Items.Add(new Item1 { Name = "Item 1" });
+        await context.SaveChangesAsync();
+
+        context.ChangeTracker.Clear();
+        var item = await context.Items.FirstAsync();
+        Assert.NotNull(item);
+        Assert.Equal("Item 1", item.Name);
+    }
+
+    [ConditionalFact]
+    public virtual async Task Can_read_original_values_with_shared_complex_property_column()
+    {
+        await using var context = CreateContext();
+        await context.Database.EnsureDeletedAsync();
+        await context.Database.EnsureCreatedAsync();
+
+        context.Items.Add(new Item1 { Name = "Item 1" });
+        await context.SaveChangesAsync();
+
+        context.ChangeTracker.Clear();
+        var item = await context.Items.FirstAsync();
+        var entry = context.ChangeTracker.Entries().First();
+        var originalItem = (Item)entry.OriginalValues.ToObject();
+
+        Assert.NotNull(originalItem);
+        Assert.Equal("Item 1", originalItem.Name);
+    }
+
+    [ConditionalFact]
+    public virtual async Task Can_save_and_query_TPH_with_shared_complex_property_column_with_value()
+    {
+        await using var context = CreateContext();
+        await context.Database.EnsureDeletedAsync();
+        await context.Database.EnsureCreatedAsync();
+
+        context.Items.Add(new Item1 { Name = "Item 1", Pricing = new ItemPrice { Amount = "10.99" } });
+        await context.SaveChangesAsync();
+
+        context.ChangeTracker.Clear();
+        var item = await context.Items.OfType<Item1>().FirstAsync();
+        Assert.NotNull(item.Pricing);
+        Assert.Equal("10.99", item.Pricing.Amount);
+    }
+
+    [ConditionalFact]
+    public virtual async Task Can_read_original_values_with_shared_complex_property_column_with_value()
+    {
+        await using var context = CreateContext();
+        await context.Database.EnsureDeletedAsync();
+        await context.Database.EnsureCreatedAsync();
+
+        context.Items.Add(new Item1 { Name = "Item 1", Pricing = new ItemPrice { Amount = "10.99" } });
+        await context.SaveChangesAsync();
+
+        context.ChangeTracker.Clear();
+        var item = await context.Items.OfType<Item1>().FirstAsync();
+        var entry = context.ChangeTracker.Entries().First();
+        var originalItem = (Item)entry.OriginalValues.ToObject();
+
+        Assert.NotNull(originalItem);
+        Assert.Equal("Item 1", originalItem.Name);
+        var item1 = Assert.IsType<Item1>(originalItem);
+        Assert.NotNull(item1.Pricing);
+        Assert.Equal("10.99", item1.Pricing.Amount);
+    }
+
+    protected ItemContext CreateContext()
+        => Fixture.CreateContext();
+
+    public class TPHComplexPropertySharingFixture : SharedStoreFixtureBase<ItemContext>
+    {
+        protected override string StoreName
+            => "TPHComplexPropertySharingTest";
+
+        protected override ITestStoreFactory TestStoreFactory
+            => SqlServerTestStoreFactory.Instance;
+    }
+}
+
+public class ItemContext(DbContextOptions<ItemContext> options) : DbContext(options)
+{
+    public required DbSet<Item> Items { get; set; }
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        modelBuilder.Entity<Item>().HasDiscriminator<string>("Discriminator")
+            .HasValue<Item1>("Item1")
+            .HasValue<Item2>("Item2");
+
+        modelBuilder.Entity<Item1>().ComplexProperty(
+            x => x.Pricing, 
+            p => p.Property(a => a.Amount).HasColumnName("Price"));
+
+        modelBuilder.Entity<Item2>().ComplexProperty(
+            x => x.Pricing, 
+            p => p.Property(a => a.Amount).HasColumnName("Price"));
+    }
+}
+
+public abstract class Item
+{
+    public int Id { get; set; }
+    public required string Name { get; set; }
+}
+
+public class Item1 : Item
+{
+    public ItemPrice? Pricing { get; set; }
+}
+
+public class Item2 : Item
+{
+    public ItemPrice? Pricing { get; set; }
+}
+
+public class ItemPrice
+{
+    public required string Amount { get; init; }
+}