Virtual keyword in EF Core: .NET 10, ILazyLoader and explicit loading samples

dotnet-efcore/VirtualKeywordInEFCore/Tests/Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
 
@@ -10,10 +10,10 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="coverlet.collector" Version="6.0.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
-    <PackageReference Include="xunit" Version="2.5.3" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3" />
+    <PackageReference Include="coverlet.collector" Version="10.1.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.10.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="4.0.0" />
   </ItemGroup>
 
   <ItemGroup>

dotnet-efcore/VirtualKeywordInEFCore/Tests/VirtualKeywordInEFCoreTests.cs

@@ -55,5 +55,40 @@ public void GivenLazyLoading_WithLazyLoadingEnabledPropertySetToFalse_WhenAuthor
             Assert.False(authorHollyJackson.Books.Any());
             Assert.Empty(authorHollyJackson.Books);
         }
+
+        [Fact]
+        public void GivenInjectedLazyLoader_WhenAuthorRetrievedInFreshContext_ThenBooksLazyLoadedWithoutProxy()
+        {
+            // Arrange
+            using (var seedContext = new DataContextInjected())
+            {
+                DataSeeder.SeedInjected(seedContext);
+            }
+
+            using var context = new DataContextInjected();
+
+            // Act
+            var author = context.AuthorsInjected.First(a => a.FullName == "Freida MCFADDEN");
+
+            // Assert
+            Assert.Equal(typeof(AuthorInjected), author.GetType());
+            Assert.NotNull(author.Books);
+            Assert.Equal(2, author.Books.Count);
+        }
+
+        [Fact]
+        public void GivenNoLazyLoading_WhenCollectionExplicitlyLoaded_ThenEmptyCollectionIsFilled()
+        {
+            // Arrange
+            using var context = new DataContextWithoutLazyLoading();
+            var author = context.Authors.First(a => a.FullName == "Lucy FOLEY");
+            Assert.Empty(author.Books);
+
+            // Act
+            context.Entry(author).Collection(a => a.Books).Load();
+
+            // Assert
+            Assert.Equal(4, author.Books.Count);
+        }
     }
 }

dotnet-efcore/VirtualKeywordInEFCore/VirtualKeywordInEFCore/Models/AuthorInjected.cs

@@ -0,0 +1,24 @@
+using Microsoft.EntityFrameworkCore.Infrastructure;
+
+namespace VirtualKeywordInEFCore.Models
+{
+    public class AuthorInjected
+    {
+        private ICollection<BookInjected>? _books;
+
+        public AuthorInjected() { }
+
+        private AuthorInjected(ILazyLoader lazyLoader) => LazyLoader = lazyLoader;
+
+        private ILazyLoader? LazyLoader { get; set; }
+
+        public int AuthorInjectedId { get; set; }
+        public string? FullName { get; set; }
+
+        public ICollection<BookInjected>? Books
+        {
+            get => LazyLoader.Load(this, ref _books);
+            set => _books = value;
+        }
+    }
+}

dotnet-efcore/VirtualKeywordInEFCore/VirtualKeywordInEFCore/Models/Book.cs

@@ -8,6 +8,6 @@ public class Book
         public int BookId { get; set; }
         public string? Title { get; set; }
         public int AuthorId { get; set; }
-        public Author Author { get; set; }
+        public Author Author { get; set; } = null!;
     }
 }

dotnet-efcore/VirtualKeywordInEFCore/VirtualKeywordInEFCore/Models/BookInjected.cs

@@ -0,0 +1,9 @@
+namespace VirtualKeywordInEFCore.Models
+{
+    public class BookInjected
+    {
+        public int BookInjectedId { get; set; }
+        public string? Title { get; set; }
+        public int AuthorInjectedId { get; set; }
+    }
+}

dotnet-efcore/VirtualKeywordInEFCore/VirtualKeywordInEFCore/Models/BookLazy.cs

@@ -8,6 +8,6 @@ public class BookLazy
         public int BookId { get; set; }
         public string? Title { get; set; }
         public int AuthorId { get; set; }
-        public virtual AuthorLazy Author { get; set; }
+        public virtual AuthorLazy Author { get; set; } = null!;
     }
 }

dotnet-efcore/VirtualKeywordInEFCore/VirtualKeywordInEFCore/Models/DataContextInjected.cs

@@ -0,0 +1,25 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace VirtualKeywordInEFCore.Models
+{
+    public class DataContextInjected : DbContext
+    {
+        protected override void OnConfiguring(DbContextOptionsBuilder options)
+        {
+            options.UseSqlite("DataSource=LibraryInjected.db");
+
+            base.OnConfiguring(options);
+        }
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+        {
+            modelBuilder.Entity<AuthorInjected>()
+                .HasMany(a => a.Books)
+                .WithOne()
+                .HasForeignKey(b => b.AuthorInjectedId);
+        }
+
+        public DbSet<AuthorInjected> AuthorsInjected { get; set; }
+        public DbSet<BookInjected> BooksInjected { get; set; }
+    }
+}

dotnet-efcore/VirtualKeywordInEFCore/VirtualKeywordInEFCore/Models/DataSeeder.cs

@@ -64,5 +64,27 @@ public static void SeedLazy(DataContextLazyLoading contextLazy)
             contextLazy.AddRange(booksLazy);
             contextLazy.SaveChanges();
         }
+
+        public static void SeedInjected(DataContextInjected contextInjected)
+        {
+            contextInjected.Database.EnsureCreated();
+            if (contextInjected.AuthorsInjected.Any())
+            {
+                return;
+            }
+
+            var authorInjected = new AuthorInjected
+            {
+                FullName = "Freida MCFADDEN",
+                Books = new List<BookInjected>
+                {
+                    new () { Title = "The Housemaid" },
+                    new () { Title = "The Coworker" }
+                }
+            };
+
+            contextInjected.Add(authorInjected);
+            contextInjected.SaveChanges();
+        }
     }
 }

dotnet-efcore/VirtualKeywordInEFCore/VirtualKeywordInEFCore/Program.cs

@@ -10,6 +10,9 @@
             LoadData();
 
             LoadDataWithLazyLoading();
+
+            LoadDataWithInjectedLazyLoader();
+            LoadDataWithExplicitLoading();
         }
 
         public static void LoadData()
@@ -21,15 +24,12 @@
             Author author;
             author = contextWithoutLazyLoading.Authors.AsNoTracking().First(a => a.FullName == "Lucy FOLEY");
 
-            if (author is not null)
-            {
-                Console.WriteLine($"Author Name: {author.FullName}");
-                Console.WriteLine($"{author.FullName}'s Books number: {author.Books.Count}");
+            Console.WriteLine($"Author Name: {author.FullName}");
+            Console.WriteLine($"{author.FullName}'s Books number: {author.Books.Count}");
 
-                foreach (var book in author.Books)
-                {
-                    Console.WriteLine($"Book Title: {book.Title}");
-                }
+            foreach (var book in author.Books)
+            {
+                Console.WriteLine($"Book Title: {book.Title}");
             }
         }
 
@@ -49,11 +49,44 @@
                 Console.WriteLine($"{nameof(AuthorLazy)} datatype: {authorLazy.GetType()}");
                 Console.WriteLine($"{nameof(BookLazy)} datatype: {authorLazy.Books?.First().GetType()}");
 
                 foreach (var bookLazy in authorLazy.Books)
                 {
                     Console.WriteLine($"Book Title: {bookLazy.Title}");
                 }
             }
         }
+
+        public static void LoadDataWithInjectedLazyLoader()
+        {
+            Console.WriteLine("\nLazy Loading with an injected ILazyLoader:");
+
+            using (var seedContext = new DataContextInjected())
+            {
+                DataSeeder.SeedInjected(seedContext);
+            }
+
+            using var context = new DataContextInjected();
+            var author = context.AuthorsInjected.First(a => a.FullName == "Freida MCFADDEN");
+
+            Console.WriteLine($"{nameof(AuthorInjected)} datatype: {author.GetType()}");
+            Console.WriteLine($"{author.FullName}'s Books number: {author.Books?.Count}");
+        }
+
+        public static void LoadDataWithExplicitLoading()
+        {
+            Console.WriteLine("\nExplicit Loading:");
+
+            using (var seedContext = new DataContextWithoutLazyLoading())
+            {
+                DataSeeder.SeedWithoutLazy(seedContext);
+            }
+
+            using var context = new DataContextWithoutLazyLoading();
+            var author = context.Authors.First(a => a.FullName == "Lucy FOLEY");
+
+            context.Entry(author).Collection(a => a.Books).Load();
+
+            Console.WriteLine($"{author.FullName}'s Books number after Load(): {author.Books.Count}");
+        }
     }
 }

dotnet-efcore/VirtualKeywordInEFCore/VirtualKeywordInEFCore/VirtualKeywordInEFCore.csproj

@@ -2,15 +2,16 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="8.0.2" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Proxies" Version="8.0.2" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="8.0.2" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="10.0.12" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Abstractions" Version="10.0.12" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Proxies" Version="10.0.12" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="10.0.12" />
   </ItemGroup>
 
 </Project>