using System;

using System.Collections.Generic;

using Microsoft.EntityFrameworkCore;

using System.Linq;

​

namespace devs

{

    class Program

    {

        static DbContextOptions<Context> options;

        static void Main(string[] args)

        {

            options = new DbContextOptionsBuilder<Context>()

                .UseInMemoryDatabase(databaseName: "devs_database")

                .Options;

            using (Context context = new Context(options))

            {

                var dep = context.Departments.Add(new Department(1, "A"));

                context.Developers.Add(new Developer(1, "aa", dep.Entity));

                context.Developers.Add(new Developer(2, "ab", dep.Entity));

                dep = context.Departments.Add(new Department(2, "B"));

                context.Developers.Add(new Developer(3, "ba", dep.Entity));

                context.Developers.Add(new Developer(4, "bb", dep.Entity));

                context.SaveChanges();

            }

            Console.WriteLine(string.Join(", ",GetDevs("A")));

        }

​

        public static List<Developer> GetDevs(string DepartmentName)

        {

            using Context ctx = new(options);

            // pouze vyvojari

            //return ctx.Developers.Where(d => d.Department.DepartmentName == DepartmentName).ToList();

            // vyvojari i oddeleni

            return ctx.Developers.Include(d=>d.Department).Where(d => d.Department.DepartmentName == DepartmentName).ToList();

        }

    }

​

    public class Context : DbContext

    {

        public DbSet<Developer> Developers { get; set; } 

        public DbSet<Department> Departments { get; set; }

​

        public Context(DbContextOptions<Context> options)

            : base(options){ }

​

​

    }

​

    public record Developer(int Id, string FirstName="", Department Department=null)

    {

        internal Developer() : this(0) { }

    }

    public record Department(int Id, string DepartmentName="")

    {

        internal Department() : this(0) { }

    }

}

​