Added entity framework helpers.

src/HotChocolate/Data/HotChocolate.Data.sln

@@ -66,6 +66,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HotChocolate.Data.Sorting.I
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HotChocolate.Data.Sorting.SqlLite.Tests", "test\Data.Sorting.SqlLite.Tests\HotChocolate.Data.Sorting.SqlLite.Tests.csproj", "{D445A9BB-D068-496A-B261-609799F95915}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HotChocolate.Data.EntityFramework", "src\EntityFramework\HotChocolate.Data.EntityFramework.csproj", "{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HotChocolate.Data.EntityFramework.Tests", "test\Data.EntityFramework.Tests\HotChocolate.Data.EntityFramework.Tests.csproj", "{16FB6511-AE94-46C4-9652-2665C6816546}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -102,6 +106,8 @@ Global
 		{A7269FAC-8C91-46BA-B292-221E8DE32BD3} = {4EE990B2-C327-46DA-8FE8-F95AC228E47F}
 		{E5E0D684-4FF6-4124-8ADB-9E96A3FDA6FA} = {4EE990B2-C327-46DA-8FE8-F95AC228E47F}
 		{D445A9BB-D068-496A-B261-609799F95915} = {4EE990B2-C327-46DA-8FE8-F95AC228E47F}
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303} = {91887A91-7B1C-4287-A1E0-BD4E0DAF24C7}
+		{16FB6511-AE94-46C4-9652-2665C6816546} = {4EE990B2-C327-46DA-8FE8-F95AC228E47F}
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
 		{D68A0AB9-871A-487B-8D12-1A7544D81B9E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
@@ -380,5 +386,29 @@ Global
 		{D445A9BB-D068-496A-B261-609799F95915}.Release|x64.Build.0 = Release|Any CPU
 		{D445A9BB-D068-496A-B261-609799F95915}.Release|x86.ActiveCfg = Release|Any CPU
 		{D445A9BB-D068-496A-B261-609799F95915}.Release|x86.Build.0 = Release|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Debug|x64.Build.0 = Debug|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Debug|x86.Build.0 = Debug|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Release|Any CPU.Build.0 = Release|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Release|x64.ActiveCfg = Release|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Release|x64.Build.0 = Release|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Release|x86.ActiveCfg = Release|Any CPU
+		{0E4E8E6F-A65C-42C0-BE9F-DFA002E59303}.Release|x86.Build.0 = Release|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Debug|x64.Build.0 = Debug|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Debug|x86.Build.0 = Debug|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Release|Any CPU.Build.0 = Release|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Release|x64.ActiveCfg = Release|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Release|x64.Build.0 = Release|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Release|x86.ActiveCfg = Release|Any CPU
+		{16FB6511-AE94-46C4-9652-2665C6816546}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal

src/HotChocolate/Data/src/EntityFramework/Extensions/EntityFrameworkObjectFieldDescriptorExtensions.cs

@@ -0,0 +1,60 @@
+using System;
+using System.Linq;
+using HotChocolate.Data;
+using HotChocolate.Resolvers;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using static HotChocolate.Resolvers.FieldClassMiddlewareFactory;
+
+namespace HotChocolate.Types
+{
+    public static class EntityFrameworkObjectFieldDescriptorExtensions
+    {
+        public static IObjectFieldDescriptor UseDbContext<TDbContext>(
+            this IObjectFieldDescriptor descriptor)
+            where TDbContext : DbContext
+        {
+            string scopedServiceName = typeof(TDbContext).FullName ?? typeof(TDbContext).Name;
+            FieldMiddleware placeholder = next => context => throw new NotSupportedException();
+
+            descriptor
+                .Use(next => async context =>
+                {
+                    await using TDbContext dbContext = context.Services
+                        .GetRequiredService<IDbContextFactory<TDbContext>>()
+                        .CreateDbContext();
+
+                    try
+                    {
+                        context.SetLocalValue(scopedServiceName, dbContext);
+                        await next(context).ConfigureAwait(false);
+                    }
+                    finally
+                    {
+                        context.RemoveLocalValue(scopedServiceName);
+                    }
+                })
+                .Use(placeholder)
+                .Extend()
+                .OnBeforeNaming((c, d) =>
+                {
+                    if (d.ResultType is not null &&
+                        typeof(IQueryable).IsAssignableFrom(d.ResultType) &&
+                        d.ResultType.IsGenericType)
+                    {
+                        Type entity = d.ResultType.GenericTypeArguments[0];
+                        Type middleware = typeof(ToListMiddleware<>).MakeGenericType(entity);
+
+                        var index = d.MiddlewareComponents.IndexOf(placeholder);
+                        d.MiddlewareComponents[index] = Create(middleware);
+                    }
+                    else
+                    {
+                        d.MiddlewareComponents.Remove(placeholder);
+                    }
+                });
+
+            return descriptor;
+        }
+    }
+}

src/HotChocolate/Data/src/EntityFramework/HotChocolate.Data.EntityFramework.csproj

@@ -0,0 +1,34 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <PackageId>HotChocolate.Data.EntityFramework</PackageId>
+    <AssemblyName>HotChocolate.Data</AssemblyName>
+    <RootNamespace>HotChocolate.Data</RootNamespace>
+    <NoWarn>$(NoWarn);CA1062</NoWarn>
+    <TargetFrameworks>netstandard2.1</TargetFrameworks>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\Core\src\Core\HotChocolate.Core.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="5.0.0-rc.2.20475.6" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Update="Properties\EntityFrameworkResources.resx">
+      <Generator>ResXFileCodeGenerator</Generator>
+      <LastGenOutput>EntityFrameworkResources.Designer.cs</LastGenOutput>
+    </EmbeddedResource>
+  </ItemGroup>
+
+  <ItemGroup>
+    <Compile Update="Properties\EntityFrameworkResources.Designer.cs">
+      <DesignTime>True</DesignTime>
+      <AutoGen>True</AutoGen>
+      <DependentUpon>EntityFrameworkResources.resx</DependentUpon>
+    </Compile>
+  </ItemGroup>
+
+</Project>

src/HotChocolate/Data/src/EntityFramework/Properties/EntityFrameworkResources.resx

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<root>
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:element name="root" msdata:IsDataSet="true">
+
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>1.3</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <data name="UseDbContextAttribute_OnConfigure_NoDbContextType" xml:space="preserve">
+    <value>The `{0}` must inherit from `Microsoft.EntityFrameworkCore`.</value>
+  </data>
+</root>

src/HotChocolate/Data/src/EntityFramework/ToListMiddleware.cs

@@ -0,0 +1,29 @@
+using System.Linq;
+using System.Threading.Tasks;
+using HotChocolate.Resolvers;
+using Microsoft.EntityFrameworkCore;
+
+namespace HotChocolate.Data
+{
+    internal class ToListMiddleware<TEntity>
+    {
+        private readonly FieldDelegate _next;
+
+        public ToListMiddleware(FieldDelegate next)
+        {
+            _next = next;
+        }
+
+        public async ValueTask InvokeAsync(IMiddlewareContext context)
+        {
+            await _next(context).ConfigureAwait(false);
+
+            if (context.Result is IQueryable<TEntity> queryable)
+            {
+                context.Result = await queryable
+                    .ToListAsync(context.RequestAborted)
+                    .ConfigureAwait(false);
+            }
+        }
+    }
+}

src/HotChocolate/Data/src/EntityFramework/UseDbContextAttribute.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Reflection;
+using HotChocolate.Data.Properties;
+using HotChocolate.Types;
+using HotChocolate.Types.Descriptors;
+using Microsoft.EntityFrameworkCore;
+using static HotChocolate.Data.Properties.EntityFrameworkResources;
+
+namespace HotChocolate.Data
+{
+    public class UseDbContextAttribute : ObjectFieldDescriptorAttribute
+    {
+        private static readonly MethodInfo _useDbContext =
+            typeof(EntityFrameworkObjectFieldDescriptorExtensions)
+                .GetMethod(nameof(EntityFrameworkObjectFieldDescriptorExtensions.UseDbContext),
+                    BindingFlags.Public | BindingFlags.Static)!;
+
+        private readonly Type _dbContext;
+
+        public UseDbContextAttribute(Type dbContext)
+        {
+            _dbContext = dbContext;
+        }
+
+        public override void OnConfigure(
+            IDescriptorContext context,
+            IObjectFieldDescriptor descriptor,
+            MemberInfo member)
+        {
+            if (!typeof(DbContext).IsAssignableFrom(_dbContext))
+            {
+                throw new SchemaException(
+                    SchemaErrorBuilder.New()
+                        .SetMessage(
+                            UseDbContextAttribute_OnConfigure_NoDbContextType,
+                            _dbContext.FullName ?? _dbContext.Name)
+                        .SetExtension(nameof(member), member)
+                        .Build());
+            }
+
+            _useDbContext.MakeGenericMethod(_dbContext).Invoke(null, new object?[] { descriptor });
+        }
+    }
+}

src/HotChocolate/Data/test/Data.EntityFramework.Tests/Author.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace HotChocolate.Data
+{
+    public class Author
+    {
+        [Key]
+        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+        public int Id { get; set; }
+
+        [Required]
+        public string? Name { get; set; }
+
+        public virtual ICollection<Book> Books { get; set; } =
+            new List<Book>();
+    }
+}

src/HotChocolate/Data/test/Data.EntityFramework.Tests/Book.cs

@@ -0,0 +1,20 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace HotChocolate.Data
+{
+    public class Book
+    {
+        [Key]
+        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+        public int Id { get; set; }
+
+        [Required]
+        public int AuthorId { get; set; }
+
+        [Required]
+        public string? Title { get; set; }
+
+        public virtual Author? Author { get; set; }
+    }
+}

src/HotChocolate/Data/test/Data.EntityFramework.Tests/BookContext.cs

@@ -0,0 +1,23 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace HotChocolate.Data
+{
+    public class BookContext : DbContext
+    {
+        public BookContext(DbContextOptions options) : base(options)
+        {
+        }
+
+        public DbSet<Book> Books { get; set; } = default!;
+
+        public DbSet<Author> Authors { get; set; } = default!;
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+        {
+            modelBuilder.Entity<Author>()
+                .HasMany(t => t.Books)
+                .WithOne(t => t.Author!)
+                .HasForeignKey(t => t.AuthorId);
+        }
+    }
+}

src/HotChocolate/Data/test/Data.EntityFramework.Tests/HotChocolate.Data.EntityFramework.Tests.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <RootNamespace>HotChocolate.Data</RootNamespace>
+    <TargetFrameworks>net5.0; netcoreapp3.1</TargetFrameworks>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\Core\test\Types.Tests\HotChocolate.Types.Tests.csproj" />
+    <ProjectReference Include="..\..\src\EntityFramework\HotChocolate.Data.EntityFramework.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="5.0.0-rc.2.20475.6" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Update="Properties\EfResources.resx">
+      <Generator>ResXFileCodeGenerator</Generator>
+      <LastGenOutput>EfResources.Designer.cs</LastGenOutput>
+    </EmbeddedResource>
+  </ItemGroup>
+
+</Project>