Document ToInMemoryQuery and re-introduce sample code (#3745)

Fixes #3744

entity-framework/core/modeling/entity-types.md

@@ -98,7 +98,7 @@ Entity types can be mapped to database views using the Fluent API.
  Mapping to a view will remove the default table mapping, but starting with EF 5.0 the entity type can also be mapped to a table explicitly. In this case the query mapping will be used for queries and the table mapping will be used for updates.
 
 > [!TIP]
-> To test entity types mapped to views using the in-memory provider map them to a query via `ToInMemoryQuery`. See a [runnable sample](https://github.com/dotnet/EntityFramework.Docs/tree/main/samples/core/Miscellaneous/Testing/ItemsWebApi/) using this technique for more details.
+> To test keyless entity types mapped to views using the in-memory provider, map them to a query via <xref:Microsoft.EntityFrameworkCore.InMemoryEntityTypeBuilderExtensions.ToInMemoryQuery%2A>. See the [in-memory provider docs](xref:core/testing/testing-without-the-database#in-memory-provider) for more information.
 
 ## Table-valued function mapping
 

entity-framework/core/modeling/keyless-entity-types.md

@@ -95,4 +95,4 @@ Finally, we can query the database view in the standard way:
 > Note we have also defined a context level query property (DbSet) to act as a root for queries against this type.
 
 > [!TIP]
-> To test keyless entity types mapped to views using the in-memory provider map them to a query via `ToInMemoryQuery`. See a [runnable sample](https://github.com/dotnet/EntityFramework.Docs/tree/main/samples/core/Miscellaneous/Testing/ItemsWebApi/) using this technique for more details.
+> To test keyless entity types mapped to views using the in-memory provider, map them to a query via <xref:Microsoft.EntityFrameworkCore.InMemoryEntityTypeBuilderExtensions.ToInMemoryQuery%2A>. See the [in-memory provider docs](xref:core/testing/testing-without-the-database#in-memory-provider) for more information.

entity-framework/core/testing/testing-without-the-database.md

@@ -48,16 +48,26 @@ To use in-memory SQLite, it's important to understand that a new database is cre
 
 Tests can now call `CreateContext`, which returns a context using the connection we set up in the constructor, ensuring we have a clean database with the seeded data.
 
-The full sample code can be viewed [here](https://github.com/dotnet/EntityFramework.Docs/blob/main/samples/core/Testing/TestingWithoutTheDatabase/SqliteInMemoryBloggingControllerTest.cs).
+The full sample code for SQLite in-memory testing can be viewed [here](https://github.com/dotnet/EntityFramework.Docs/blob/main/samples/core/Testing/TestingWithoutTheDatabase/SqliteInMemoryBloggingControllerTest.cs).
 
 ## In-memory provider
 
 As discussed in the [testing overview page](xref:core/testing/choosing-a-testing-strategy#inmemory-as-a-database-fake), using the in-memory provider for testing is strongly discouraged; [consider using SQLite instead](#sqlite-in-memory), or [implementing the repository pattern](#repository-pattern). If you've decided to use in-memory, here is a typical test class constructor that sets up and seeds a new in-memory database before each test:
 
 [!code-csharp[Main](../../../samples/core/Testing/TestingWithoutTheDatabase/InMemoryBloggingControllerTest.cs?name=Constructor)]
 
+The full sample code for in-memory testing can be viewed [here](https://github.com/dotnet/EntityFramework.Docs/blob/main/samples/core/Testing/TestingWithoutTheDatabase/InMemoryBloggingControllerTest.cs).
+
+### In-memory database naming
+
 In-memory databases are identified by a simple, string name, and it's possible to connect to the same database several times by providing the same name (this is why the sample above must call `EnsureDeleted` before each test). However, note that in-memory databases are rooted in the context's internal service provider; while in most cases contexts share the same service provider, configuring contexts with different options may trigger the use of a new internal service provider. When that's the case, explicitly pass the same instance of <xref:Microsoft.EntityFrameworkCore.Storage.InMemoryDatabaseRoot> to `UseInMemoryDatabase` for all contexts which should share in-memory databases (this is typically done by having a static `InMemoryDatabaseRoot` field).
 
+### Transactions
+
 Note that by default, if a transaction is started, the in-memory provider will throw an exception since transactions aren't supported. You may wish to have transactions silently ignored instead, by configuring EF Core to ignore `InMemoryEventId.TransactionIgnoredWarning` as in the above sample. However, if your code actually relies on transactional semantics - e.g. depends on rollback actually rolling back changes - your test won't work.
 
-The full sample code can be viewed [here](https://github.com/dotnet/EntityFramework.Docs/blob/main/samples/core/Testing/TestingWithoutTheDatabase/InMemoryBloggingControllerTest.cs).
+### Views
+
+The in-memory provider allows the definition of views via LINQ queries, using <xref:Microsoft.EntityFrameworkCore.InMemoryEntityTypeBuilderExtensions.ToInMemoryQuery%2A>:
+
+[!code-csharp[Main](../../../samples/core/Testing/TestingWithoutTheDatabase/InMemoryBloggingControllerTest.cs?name=ToInMemoryQuery)]

samples/core/Testing/BusinessLogic/BloggingContext.cs

@@ -5,19 +5,22 @@ namespace EF.Testing.BusinessLogic
 {
     public class BloggingContext : DbContext
     {
+        private readonly Action<BloggingContext, ModelBuilder> _modelCustomizer;
+
         #region Constructors
         public BloggingContext()
         {
         }
 
-        public BloggingContext(DbContextOptions<BloggingContext> options)
+        public BloggingContext(DbContextOptions<BloggingContext> options, Action<BloggingContext, ModelBuilder> modelCustomizer = null)
             : base(options)
         {
+            _modelCustomizer = modelCustomizer;
         }
-
         #endregion
 
         public DbSet<Blog> Blogs => Set<Blog>();
+        public DbSet<UrlResource> UrlResources => Set<UrlResource>();
 
         #region OnConfiguring
         protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
@@ -29,5 +32,16 @@ protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
             }
         }
         #endregion
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+        {
+            modelBuilder.Entity<UrlResource>().HasNoKey()
+                .ToView("AllResources");
+
+            if (_modelCustomizer is not null)
+            {
+                _modelCustomizer(this, modelBuilder);
+            }
+        }
     }
 }

samples/core/Testing/BusinessLogic/BusinessLogic.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="6.0.0" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="6.0.2" />
   </ItemGroup>
 
 </Project>

samples/core/Testing/BusinessLogic/UrlResource.cs

@@ -0,0 +1,7 @@
+namespace EF.Testing.BusinessLogic
+{
+    public class UrlResource
+    {
+        public string Url { get; set; }
+    }
+}

samples/core/Testing/TestingWithoutTheDatabase/InMemoryBloggingControllerTest.cs

@@ -83,6 +83,12 @@ public void UpdateBlogUrl()
             Assert.Equal("http://blog2_updated.com", blog.Url);
         }
 
-        BloggingContext CreateContext() => new BloggingContext(_contextOptions);
+        BloggingContext CreateContext() => new BloggingContext(_contextOptions, (context, modelBuilder) =>
+        {
+            #region ToInMemoryQuery
+            modelBuilder.Entity<UrlResource>()
+                .ToInMemoryQuery(() => context.Blogs.Select(b => new UrlResource { Url = b.Url }));
+            #endregion
+        });
     }
 }

samples/core/Testing/TestingWithoutTheDatabase/SqliteInMemoryBloggingControllerTest.cs

@@ -30,7 +30,15 @@ public SqliteInMemoryBloggingControllerTest()
             // Create the schema and seed some data
             using var context = new BloggingContext(_contextOptions);
 
-            context.Database.EnsureCreated();
+            if (context.Database.EnsureCreated())
+            {
+                using var viewCommand = context.Database.GetDbConnection().CreateCommand();
+                viewCommand.CommandText = @"
+CREATE VIEW AllResources AS
+SELECT Url
+FROM Blogs;";
+                viewCommand.ExecuteNonQuery();
+            }
 
             context.AddRange(
                 new Blog { Name = "Blog1", Url = "http://blog1.com" },

samples/core/Testing/TestingWithoutTheDatabase/TestingWithoutTheDatabase.csproj

@@ -8,8 +8,8 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="5.0.2" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="5.0.2" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="6.0.2" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="6.0.2" />
 
     <PackageReference Include="Moq" Version="4.16.1" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />