ConsoleApplication2-Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Data.Entity;
using Microsoft.Data.Entity.Infrastructure;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

using ConsoleApplication2.Model;

namespace ConsoleApplication2
{
    class Program
    {
        public static IConfigurationRoot Configuration { get; set; }
        public static ApplicationDbContext myDbContext;

        static void Main(string[] args)
        {
            Startup(args);
            DebugPrint("Start");
            Seed(myDbContext);
            Test1(myDbContext);
            Test2(myDbContext);
            DebugPrint("Press Enter to quit:");
            Console.ReadLine();
        }

        private static void Test1(ApplicationDbContext myDbContext)
        {
            var ggparent = (from ggp in myDbContext.GrandGrandParent
                            .Include(ggp => ggp.GrandParents)
                            .ThenInclude(x => x.Parents)
                            where ggp.ID == 3
                            select ggp).FirstOrDefault();
            DebugPrint("GrandGrandParent:");
            DebugPrint(ggparent);

            DebugPrint("WithParents:");
            DebugPrint(ggparent);
            foreach (var gparent in ggparent.GrandParents)
            {
                DebugPrint(gparent);
                if (gparent.Parents == null)
                {
                    gparent.Parents = (from p in myDbContext.Parent where p.GrandParent.ID == gparent.ID select p).ToList();
                }
                foreach (var parent in gparent.Parents)
                {
                    DebugPrint(parent);
                    parent.Children = (from c in myDbContext.Child where c.Parent.ID == parent.ID select c).ToList();
                    foreach (var child in parent.Children)
                    {
                        DebugPrint(child);
                    }
                }
            }
            int changeCount = myDbContext.SaveChanges();
            DebugPrint(string.Format("ChangeCount={0}", changeCount));
        }


        private static void Test2(ApplicationDbContext myDbContext)
        {
            DebugPrint("Second try");

            var gparents = from gp in myDbContext.GrandParent
                            .Include(gparent => gparent.GrandGrandParent)
                            .Include(gparent => gparent.Parents)
                            .ThenInclude(children => children.Select(child => child.ID))
                           where gp.GrandGrandParent.ID == 2
                           select gp;
            DebugPrint(gparents.FirstOrDefault().GrandGrandParent);
            foreach (var gparent in gparents)
            {
                DebugPrint(gparent);
                if (gparent.Parents == null)
                {
                    gparent.Parents = (from p in myDbContext.Parent where p.GrandParent.ID == gparent.ID select p).ToList();
                }
                foreach (var parent in gparent.Parents)
                {
                    DebugPrint(parent);
                    if (parent.Children == null)
                    {
                        parent.Children = (from c in myDbContext.Child where c.Parent.ID == parent.ID select c).ToList();
                    }
                    foreach (var child in parent.Children)
                    {
                        DebugPrint(child);
                    }
                }
            }
        }

        private static void Seed(ApplicationDbContext myDbContext)
        {
            GrandGrandParent grandgrandparent;
            GrandParent grandparent;
            Parent parent;
            Child child;
            int g = 1;
            if (myDbContext.GrandGrandParent.FirstOrDefault() != null)
            {
                return;
            }
            for (int i = 0; i < 4; i++)
            {
                grandgrandparent = new GrandGrandParent() { Name = FormatName("ggp", i, g++) };
                myDbContext.GrandGrandParent.Add(grandgrandparent);
                for (int j = 0; j < 4; j++)
                {
                    grandparent = new GrandParent() { Name = FormatName("gp", j, g++), GrandGrandParent = grandgrandparent };
                    grandgrandparent.GrandParents.Add(grandparent);
                    myDbContext.GrandParent.Add(grandparent);
                    for (int k = 0; k < 4; k++)
                    {
                        parent = new Parent() { Name = FormatName("p", k, g++), GrandParent = grandparent };
                        grandparent.Parents.Add(parent);
                        myDbContext.Parent.Add(parent);
                        for (int l = 0; l < 4; l++)
                        {
                            child = new Child() { Name = FormatName("c", l, g++), Parent = parent };
                            parent.Children.Add(child);
                            myDbContext.Child.Add(child);
                        }
                    }
                }
            }
            myDbContext.SaveChanges();
        }

        private static string FormatName(string prefix, int local, int global)
        {
            return String.Format("{0}-{1} ({2})", prefix, local, global);
        }


        private static void DebugPrint(GrandGrandParent ggp)
        {
            DebugPrint(ggp.Name);
        }
        private static void DebugPrint(GrandParent gp)
        {
            DebugPrint("  " + gp.Name);
        }
        private static void DebugPrint(Parent p)
        {
            DebugPrint("    " + p.Name);
        }
        private static void DebugPrint(Child c)
        {
            DebugPrint("      " + c.Name);
        }
        private static void DebugPrint(string s)
        {
            //System.Diagnostics.Debug.WriteLine(s);
            Console.WriteLine(s);
        }

        public static void Startup(string[] args)
        {
            var builder = new ConfigurationBuilder();
            builder.AddEnvironmentVariables();
            builder.AddCommandLine(args);
            Configuration = builder.Build();
            myDbContext = new ApplicationDbContext();
        }
    }
}