// @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

        using (var context = new EntityContext())

        {

            context.BulkInsert(CustomerData());

            context.BulkInsert(InvoiceData());

        }

        using (var context = new EntityContext())

        {

            var customers = context.Customers

                .Include(c => c.Invoices)

                .ToList();

​

            var list = customers.Where(c => c.TotalInvoices > 0)

                .ToList();

            FiddleHelper.WriteTable(list);

        }

    }

    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() { InvoiceDate = new DateTime(2018,1,5), CustomerID = 1},

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

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

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

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

        };

        return list;

    }

​

    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 int TotalInvoices 

        {

            get { return Invoices.Count; }

        }

    }

    public class Invoice

    {

        public int InvoiceID { get; set; }

        public DateTime InvoiceDate { get; set; }

        public int CustomerID { get; set; }

        public Customer Customer { get; set; }

    }

}