inheritance - Your object's family tree - base class, sub class, method, virtual, override

Head First C#:
A Learner's Guide to Real-World Programming
with C# and .NET Core
楽天ブックス

開発環境

Head First C#: A Learner’s Guide to Real-World Programming with C# and .NET Core (Andrew Stellman(著)、Jennifer Greene(著)、O’Reilly Media)のChapter 6(inheritance - Your object’s family tree)、p.293(Exercise)の解答を求めてみる。

コード

Program.cs

using System;

namespace MyFirstConsoleApp
{
    class A
    {
        public int ivar = 7;
        public virtual string m1()
        {
            return "A's m1, ";
        }
        public string m2()
        {
            return "A's m2, ";
        }
        public virtual string m3()
        {
            return "A's m3, ";
        }
    }
    class B: A
    {
        public override string m1()
        {
            return "B's m1, ";
        }
    }
    class C:B
    {
        public override string m3()
        {
            return "C's m3, " + (ivar + 6);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            A a = new A();
            B b = new B();
            C c = new C();
            A a2 = new C();
            string q = b.m1() + c.m2() + a.m3();
            Console.WriteLine(q == "B's m1, A's m2, A's m3, ");
            q = c.m1() + c.m2() + c.m3();
            Console.WriteLine(q == "B's m1, A's m2, C's m3, 13");
            q = a.m1() + b.m2() + c.m3();
            Console.WriteLine(q == "A's m1, A's m2, C's m3, 13");
            q = a2.m1() + a2.m2() + a2.m3();
            Console.WriteLine(q == "B's m1, A's m2, C's m3, 13");
        }
    }
}

入出力結果(Terminal, Zsh)

True
True
True
True