using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

​

namespace ConsoleApp17

{

    public class BaseClass {

        string name = "I am base";

        public Type type;

        public enum Type { 

            a,b,c,d

        }

        public BaseClass(Type type) {

            this.type = type;

        }

    }

​

    public class DerivedClass1 : BaseClass

    {

        string name = "I am derivedA";

​

        public DerivedClass1(): base(Type.a) {

        }

    }

​

​

    public class DerivedClass2 : BaseClass

    {

        string name = "I am derivedB";

        public DerivedClass2() : base(Type.b)

        {

​

        }

    }

​

    public class Foo

    {

        public Dictionary<BaseClass.Type, List<BaseClass>> dict = new Dictionary<BaseClass.Type, List<BaseClass>>();

​

        public Foo() {

​

            dict[BaseClass.Type.a] = new List<BaseClass>();

            dict[BaseClass.Type.b] = new List<BaseClass>();

            dict[BaseClass.Type.c] = new List<BaseClass>();

            dict[BaseClass.Type.d] = new List<BaseClass>();

​

            AddItem(new DerivedClass1());

            AddItem(new DerivedClass1());

​

            AddItem(new DerivedClass2());

            AddItem(new DerivedClass2());

            AddItem(new DerivedClass2());

        }

​

        public IEnumerable<T> GetEnumByType<T>(BaseClass.Type type) where T : BaseClass

        {

            if (dict.ContainsKey(type))

            {

                if (type == BaseClass.Type.a)

                {

                    Console.WriteLine($"are equal:  { object.ReferenceEquals(dict[type].Cast<T>(), dict[BaseClass.Type.a])}");

                }

​

                return dict[type].Cast<T>();

            }

            return null;

        }

​

        public void AddItem<T>(T item) where T : BaseClass

        {

            dict[item.type].Add(item);

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            Foo foo = new Foo();

            IEnumerable myList = foo.GetEnumByType<BaseClass>(BaseClass.Type.a);

​

            Console.WriteLine($"areEqualRef: {object.ReferenceEquals(foo.dict[BaseClass.Type.a].Cast<BaseClass>(), foo.dict[BaseClass.Type.a])}");

            Console.WriteLine($"areEqualRef: {object.ReferenceEquals(foo.dict[BaseClass.Type.a].Cast<DerivedClass1>(), foo.dict[BaseClass.Type.a])}");

            Console.ReadLine();

        }

    }

}

​