Клиент-Серверное взаимодействие

switch(str)
{
case "a":
a();
break;
case "b":
b();
break;
}

class Program
    {
        static void Main(string[] args)
        {
            var arr = new Vocaloid[] { new Miku(), new Rin(), new Len() };
 
            var handlers = Assembly.GetExecutingAssembly()
                .GetTypes()
                .Where(myType => myType.IsClass && !myType.IsAbstract && myType.IsSubclassOf(typeof(Handler)))
                .Select(type => (Handler)Activator.CreateInstance(type))
                .ToDictionary(k => k.MessageType, v => new Action<Vocaloid>(v.Play));
 
            foreach (var message in arr)
                handlers[message.GetType()](message);
        }
    }
 
    abstract class Vocaloid
    {
        internal abstract string Name { get; }
    }
 
    class Miku : Vocaloid
    {
        internal int Number => 1;
        internal DateTime Birthday => new DateTime(2007, 8, 31);
        internal override string Name => "Hatsune-Miku";
    }
 
    class Rin : Vocaloid
    {
        internal override string Name => "Kagamine-Rin";
    }
 
    class Len : Vocaloid
    {
        internal override string Name => "Kagamine-Len";
    }
 
    abstract class Handler
    {
        internal abstract Type MessageType { get; }
        internal abstract void Play(Vocaloid vocaloid);
    }
 
    abstract class Handler<T> : Handler
        where T : Vocaloid
    {
        internal override Type MessageType => typeof(T);
 
        internal override void Play(Vocaloid vocaloid)
            => Play((T)vocaloid);
 
        protected abstract void Play(T vocaloid);
    }
 
    class MikuPlayer : Handler<Miku>
    {
        protected override void Play(Miku vocaloid)
            => Console.WriteLine($"Name = {vocaloid.Name}; Year = {(new DateTime(1, 1, 1) + (DateTime.Now - vocaloid.Birthday)).Year - 1}");
    }
 
    class RinPlayer : Handler<Rin>
    {
        protected override void Play(Rin vocaloid)
            => Console.WriteLine($"Name = {vocaloid.Name}; Sex = girl");
    }
 
    class LenPlayer : Handler<Len>
    {
        protected override void Play(Len vocaloid)
            => Console.WriteLine($"Name = {vocaloid.Name}; Sex = boy");
    }