Add strongly-typed IDs and orders for use in EF Core

Author: andrewlock

StronglyTypedIdEfCore/StronglyTypedIdEfCore/Data/ApplicationDbContext.cs

@@ -13,5 +13,7 @@ public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
             : base(options)
         {
         }
+
+        public DbSet<Order> Orders { get; set; }
     }
 }

StronglyTypedIdEfCore/StronglyTypedIdEfCore/Data/CustomValueConverterSelector.cs

@@ -0,0 +1,62 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+namespace StronglyTypedId.Shop.Data
+{
+    public class CustomValueConverterSelector : ValueConverterSelector
+    {
+        private readonly ConcurrentDictionary<(Type ModelClrType, Type ProviderClrType), ValueConverterInfo> _converters
+            = new ConcurrentDictionary<(Type ModelClrType, Type ProviderClrType), ValueConverterInfo>();
+
+        public CustomValueConverterSelector(ValueConverterSelectorDependencies dependencies) : base(dependencies)
+        {
+        }
+
+        public override IEnumerable<ValueConverterInfo> Select(Type modelClrType, Type providerClrType = null)
+        {
+            foreach (var converter in base.Select(modelClrType, providerClrType))
+            {
+                yield return converter;
+            }
+
+            // Extract the "real" type T from Nullable<T> if required
+            var underlyingModelType = UnwrapNullableType(modelClrType);
+            var underlyingProviderType = UnwrapNullableType(providerClrType);
+
+            // 'null' means 'get any value converters for the modelClrType'
+            if (underlyingProviderType is null || underlyingProviderType == typeof(Guid))
+            {
+                // Try and get a nested class with the expected name. 
+                var converterType = underlyingModelType.GetNestedType("EfCoreValueConverter");
+
+                if (converterType != null)
+                {
+                    yield return _converters.GetOrAdd(
+                        (underlyingModelType, typeof(Guid)),
+                        k =>
+                        {
+                            // Create an instance of the converter whenever it's requested.
+                            Func<ValueConverterInfo, ValueConverter> factory =
+                                info => (ValueConverter) Activator.CreateInstance(converterType, info.MappingHints);
+
+                            // Build the info for our strongly-typed ID => Guid converter
+                            return new ValueConverterInfo(modelClrType, typeof(Guid), factory);
+                        }
+                    );
+                }
+            }
+        }
+
+        private static Type UnwrapNullableType(Type providerClrType)
+        {
+            if (providerClrType is null)
+            {
+                return null;
+            }
+
+            return Nullable.GetUnderlyingType(providerClrType) ?? providerClrType;
+        }
+    }
+}

StronglyTypedIdEfCore/StronglyTypedIdEfCore/Data/Migrations/20190420212339_OrderSchema.Designer.cs

@@ -0,0 +1,56 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace StronglyTypedIdEfCore.Data.Migrations
+{
+    public partial class OrderSchema : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "Orders",
+                columns: table => new
+                {
+                    OrderId = table.Column<Guid>(nullable: false),
+                    Name = table.Column<string>(nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_Orders", x => x.OrderId);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "OrderLine",
+                columns: table => new
+                {
+                    OrderLineId = table.Column<Guid>(nullable: false),
+                    OrderId = table.Column<Guid>(nullable: false),
+                    ProductName = table.Column<string>(nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_OrderLine", x => x.OrderLineId);
+                    table.ForeignKey(
+                        name: "FK_OrderLine_Orders_OrderId",
+                        column: x => x.OrderId,
+                        principalTable: "Orders",
+                        principalColumn: "OrderId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_OrderLine_OrderId",
+                table: "OrderLine",
+                column: "OrderId");
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "OrderLine");
+
+            migrationBuilder.DropTable(
+                name: "Orders");
+        }
+    }
+}