Polymorphism and List<T>

using System;
using System.Collections.Generic;

namespace Test.Program;

class BaseClass {
    public virtual string TypeName => typeof(BaseClass).Name;

    public int BaseOnly => 1;
}

class DerivedClass1 : BaseClass {
    public override string TypeName => this.GetType().Name;

    public virtual string DerivedFrom => this.GetType()!.BaseType!.Name;

    public int Derived1Only => 2;
}

class DerivedClass2 : DerivedClass1 {
    public int Derived2Only => 3;
}


class Program
{
    static void Main() {
        List<BaseClass> l = new();
        l.Add(new BaseClass());
        l.Add(new DerivedClass1());
        l.Add(new DerivedClass2());

        l.ForEach(c => Console.WriteLine(c switch {
            DerivedClass2 d2 => $"{d2.TypeName}:\tDerivedFrom = {d2.DerivedFrom}, Derived2Only = {d2.Derived2Only}",
            DerivedClass1 d1 => $"{d1.TypeName}:\tDerivedFrom = {d1.DerivedFrom}, Derived1Only = {d1.Derived1Only}",
            BaseClass     b  => $"{b.TypeName}:\t\tBaseOnly = {b.BaseOnly}"
        }));
    }
}