Optiomization using join

BenchmarkService.cs

@@ -183,5 +183,36 @@ public List<AuthorDTO_OptimizedStruct> GetAuthors_Optimized_Struct1()
                 .Take(2)
                 .ToList();
         }
+
+        [Benchmark]
+        public List<AuthorDTO_OptimizedStruct> GetAuthors_Optimized_Struct_Join()
+        {
+            using var dbContext = new AppDbContext();
+
+            var date = new DateTime(1900, 1, 1);
+
+            return dbContext.Authors
+                .Where(x => x.Country == "Serbia" && x.Age == 27)
+                .OrderByDescending(x => x.BooksCount)
+                .Take(2)
+                .Join(dbContext.Users, a => a.UserId, u => u.Id, (a, u) =>
+                    new AuthorDTO_OptimizedStruct
+                    {
+                        FirstName = u.FirstName,
+                        LastName = u.LastName,
+                        Email = u.Email,
+                        UserName = u.UserName,
+                        Age = a.Age,
+                        Country = a.Country,
+                        Books = a.Books.Where(b => b.Published.Year < 1900)
+                            .Select(b =>
+                                new BookDTO_OptimizedStruct
+                                {
+                                    Title = b.Name,
+                                    PublishedYear = b.Published.Year
+                                })
+                    })
+                .ToList();
+        }
     }
-}
+}