// Entity Framework Classic

// Doc: https://entityframework-classic.net/to-self-hierarchy-list

​

// @nuget: Z.EntityFramework.Classic

​

using System;

using System.Collections.Generic;

using System.Data.Entity;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        SeedEmployee();

        using (var context = new EntityContext())

        {

            var employees = context.Employees.Where(x => x.Name.StartsWith("Employee_"))

                .ToSelfHierarchyList(null, options => {

                    options.ColumnMappings.Add("BossID", "EmployeeID");

                    options.FlatListRecursionLevel = int.MaxValue;

                });

​

            FiddleHelper.WriteTable("1 - Employee + Boss", employees);

        }

    }

    public static void SeedEmployee()

    {

        using (var context = new EntityContext())

        {

            var ceo_1 = new Employee() { Name = "CEO_1" };

            context.Employees.AddRange(new List<Employee>() { ceo_1 });

            context.BatchSaveChanges();

            var boss_1 = new Employee() { Name = "Boss_1", BossID = ceo_1.EmployeeID };

            var boss_2 = new Employee() { Name = "Boss_2", BossID = ceo_1.EmployeeID };

            context.Employees.AddRange(new List<Employee>() { boss_1, boss_2 });

            context.BatchSaveChanges();

            var employee_1 = new Employee() { Name = "Employee_1", BossID = boss_1.EmployeeID };

            var employee_2 = new Employee() { Name = "Employee_2", BossID = boss_2.EmployeeID };

            var employee_3 = new Employee() { Name = "Employee_3", BossID = boss_2.EmployeeID };

            context.Employees.AddRange(new List<Employee>() { employee_1, employee_2, employee_3 });

            context.BatchSaveChanges();

        }

    }

​

    public class EntityContext : DbContext

    {

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

        {

​

        }

        public DbSet<Employee> Employees { get; set; }

    }

    public class Employee

    {

        public int EmployeeID { get; set; }

        public string Name { get; set; }

        public int BossID { get; set; }

    }

}