// Entity Framework Classic

// Doc: https://entityframework-classic.net/query-include-optimized

​

// @nuget: Z.EntityFramework.Classic

// @nuget: Z.EntityFramework.Plus.QueryIncludeOptimized.EFClassic

​

using System;

using System.Collections.Generic;

using System.Data.Entity;

using System.Linq;

using Z.Expressions;

using Z.EntityFramework.Plus;

public class Program

{

    public static void Main()

    {

        GenerateData();

        using (var context = new EntityContext())

        {

            var query = context.Customers.IncludeOptimized(x => x.Invoice);

            FiddleHelper.WriteTable("Invoice", query.ToList().Select( x => x.Invoice));

        }       

    }

    public static void GenerateData()

    {

        List<Customer> list = new List<Customer>() {

                        new Customer() { Invoice = new Invoice() { Description = "Invoice_A"}}  

                    };

        // BulkInsert: INCLUDE child entities

        using (var context = new EntityContext())

        {

            context.BulkInsert(list, options => options.IncludeGraph = true);

        }

    }

​

    public class EntityContext : DbContext

    {

        public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())

        {

​

        }

        public DbSet<Invoice> Invoices { get; set; }

        public DbSet<Customer> Customers { get; set; }

    }

    public class Customer

    {

        public int CustomerID { get; set; }

        public string Name { get; set; }

        public string Description { get; set; }

        public Invoice Invoice { get; set; }

    }

    public class Invoice

    {

        public int InvoiceID { get; set; }

        public string Description { get; set; }

    }

}