Add regression test for issue#12761

test/EFCore.Specification.Tests/LazyLoadProxyTestBase.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations.Schema;
+using System.Diagnostics;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.EntityFrameworkCore.ChangeTracking;
@@ -1919,6 +1920,31 @@ public virtual void Lazy_loading_finds_correct_entity_type_with_alternate_model(
             }
         }
 
+        [ConditionalFact]
+        public virtual void Top_level_projection_track_entities_before_passing_to_client_method()
+        {
+            using (var context = CreateContext(lazyLoadingEnabled: true))
+            {
+                var query = (from p in context.Set<Parent>()
+                             select DtoFactory.CreateDto(p)).FirstOrDefault();
+
+                Assert.NotNull(((dynamic)query).Single);
+            }
+        }
+
+        private static class DtoFactory
+        {
+            public static object CreateDto(Parent parent)
+            {
+                return new
+                {
+                    parent.Id,
+                    parent.Single,
+                    parent.Single.ParentId
+                };
+            }
+        }
+
         public class Address
         {
             public int AddressId { get; set; }

test/EFCore.SqlServer.FunctionalTests/LazyLoadProxySqlServerTest.cs

@@ -429,6 +429,21 @@ public override async Task Load_collection(EntityState state, bool async)
             }
         }
 
+        [ConditionalFact(Skip = "Issue#1015")]
+        public override void Top_level_projection_track_entities_before_passing_to_client_method()
+        {
+            base.Top_level_projection_track_entities_before_passing_to_client_method();
+
+            Assert.Equal(
+                    @"@__p_0='707' (Nullable = true)
+
+            SELECT [e].[Id], [e].[ParentId]
+            FROM [Child] AS [e]
+            WHERE [e].[ParentId] = @__p_0",
+                                Sql,
+                                ignoreLineEndingDifferences: true);
+        }
+
         protected override void ClearLog() => Fixture.TestSqlLoggerFactory.Clear();
 
         protected override void RecordLog() => Sql = Fixture.TestSqlLoggerFactory.Sql;