// Entity Framework Classic

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

​

// @nuget: Z.EntityFramework.Classic

// @nuget: Z.EntityFramework.Plus.QueryIncludeFilter.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())

        {

            context.InvoiceItems.ToList();

            var query = context.Invoices.IncludeFilter(x => x.InvoiceItems.Take(1));

            FiddleHelper.WriteTable("InvoiceItems", query.ToList().SelectMany( x => x.InvoiceItems));

        }       

    }

    public static void GenerateData()

    {

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

                            new Invoice() { Description = "Invoice_A", InvoiceItems = new List<InvoiceItem>() }

        };

        for (int i = 0; i < 20; i++)

        {

            list.First().InvoiceItems.Add( new InvoiceItem() { Description = "InvoiceItem_" + i });

        }

        // 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<InvoiceItem> InvoiceItems { get; set; }

    }

    public class Invoice

    {

        public int InvoiceID { get; set; }

        public string Description { get; set; }

        public List<InvoiceItem> InvoiceItems { get; set; }

    }

    public class InvoiceItem

    {

        public int InvoiceItemID { get; set; }

        public string Description { get; set; }

    }

}