O Injetor de Dependencia do Felipe, dum jeitinho mais meu ;)

IoC.cs

using System;
using System.Threading;

namespace Magicas {

    public static class IoC<TInterface> {
        private static ReaderWriterLockSlim syncLock = new ReaderWriterLockSlim();
        private static TInterface singleton;
        public static TInterface Singleton => NewOrGetSingleton();

        public static Func<TInterface> Factory { get; set; }
        public static TInterface New() {
            if (Factory == null) throw new Exception("The 'Bind' is not setup yet.");
            return Factory();
        }

        private static TInterface NewOrGetSingleton()
        {
            if (Singleton != null) return Singleton;
            
            syncLock.EnterWriteLock();
            try { singleton = Factory(); }
            finally { syncLock.ExitWriteLock(); }

            return singleton;
        }
    } 

}