// @nuget: EntityFramework

// @nuget: Z.EntityFramework.Extensions

​

using System;

using System.Data.Entity;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        // Insert data

        InsertData();

        using (var context = new EntityContext())

        {

            var customers = context.Customers

                .Include(i => i.Invoices.Select(it => it.Items))

                .ToList();

            DisplayData(customers);

        }

​

    }

    public static void InsertData()

    {

        using (var context = new EntityContext())

        {

            context.BulkInsert(CustomerData());

            context.BulkInsert(InvoiceData());

            context.BulkInsert(ItemData());

        }

    }

    public static List<Customer> CustomerData() 

    {

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

        {

            new Customer() { Name ="Customer_1"},

            new Customer() { Name ="Customer_2"},

            new Customer() { Name ="Customer_3"}

        };

        return list;

    }

    public static List<Invoice> InvoiceData()

    {

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

        {

            new Invoice() { Date = new DateTime(2018,5,3), CustomerID = 1},

            new Invoice() { Date = DateTime.Now.AddDays(-5), CustomerID = 1},

            new Invoice() { Date = DateTime.Now.AddDays(-3), CustomerID = 1},

            new Invoice() { Date = new DateTime(2018,4,15), CustomerID = 2},

            new Invoice() { Date = new DateTime(2018,2,20), CustomerID = 3},

            new Invoice() { Date = new DateTime(2018,5,22), CustomerID = 3},

​

        };

        return list;

    }

    public static List<Item> ItemData()

    {

        List<Item> list = new List<Item>()

        {

            new Item() { Name = "Item 1", InvoiceID = 1},

            new Item() { Name = "Item 2", InvoiceID = 1},

            new Item() { Name = "Item 3", InvoiceID = 1},

            new Item() { Name = "Item 10", InvoiceID = 2},

            new Item() { Name = "Item 5", InvoiceID = 2},

            new Item() { Name = "Item 11", InvoiceID = 3},

            new Item() { Name = "Item 21", InvoiceID = 3},

            new Item() { Name = "Item 3", InvoiceID = 3},

            new Item() { Name = "Item 5", InvoiceID = 4},

            new Item() { Name = "Item 4", InvoiceID = 4},

            new Item() { Name = "Item 15", InvoiceID = 4},

            new Item() { Name = "Item 35", InvoiceID = 4},

            new Item() { Name = "Item 1", InvoiceID = 5},

            new Item() { Name = "Item 4", InvoiceID = 5},

            new Item() { Name = "Item 3", InvoiceID = 6},

            new Item() { Name = "Item 2", InvoiceID = 6},

            new Item() { Name = "Item 6", InvoiceID = 6},

            new Item() { Name = "Item 11", InvoiceID = 6},

            new Item() { Name = "Item 23", InvoiceID = 6},

            new Item() { Name = "Item 1", InvoiceID = 6},

            new Item() { Name = "Item 4", InvoiceID = 6},

            new Item() { Name = "Item 20", InvoiceID = 6},

        };

        return list;

    }

    public static void DisplayData(List<Customer> list)

    {

        foreach(var customer in list)

        {

            Console.WriteLine(customer.Name);

            foreach(var invoice in customer.Invoices)

            {

                Console.WriteLine("\t" + invoice.Date);

                foreach(var item in invoice.Items)

                {

                    Console.WriteLine("\t\t" + item.Name);

                }

            }

        }

    }

​

    public class EntityContext : DbContext

    {

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

        {

​

        }

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

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

    }

    public class Customer

    {

        public int CustomerID { get; set; }

        public string Name { get; set; }

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

    }

    public class Invoice

    {

        public int InvoiceID { get; set; }

        public DateTime Date { get; set; }

        public int CustomerID { get; set; }

        public Customer Customer { get; set; }

        public List<Item> Items { get; set; }

    }

    public class Item

    {

        public int ItemID { get; set; }

        public string Name { get; set; }

        public int InvoiceID { get; set; }

        public Invoice Invoice { get; set; }

    }

}