1、建立介面

 public interface ITimeProvider
    {
        DateTime CurrentDate { get; }
        string CurrentYear { get; }
    }

 public class TimeProvider : ITimeProvider
    {
        public DateTime CurrentDate { get { return DateTime.Now; } }
        public string CurrentYear { get { return DateTime.Now.Year.ToString(); } }
    }
 

 public class Assembler
    {
        private static Dictionary<Type, Type> dictionary = new Dictionary<Type, Type>();
        public Assembler()
        {
            dictionary.Add(typeof(ITimeProvider), typeof(TimeProvider));
        }
        public object Create(Type type)
        {
            if (type == null || !dictionary.ContainsKey(type)) throw new NullReferenceException();
            Type targetType = dictionary[type];
            return Activator.CreateInstance(targetType);
        }

        public T Create<T>()
        {
            return (T)Create(typeof(T));
        }
    }
 

4、客戶端呼叫

  public class Client
    {
        private ITimeProvider timeProvider;
        public Client(ITimeProvider timeProvider)
        {
            this.timeProvider = timeProvider;
        }
        public string GetYear()
        {
            return timeProvider.CurrentYear .ToString();
        }
        public string GetDatetime()
        {
            return timeProvider.CurrentDate.ToString();
        }
    }
 

     ITimeProvider timeProvider = (new Assembler()).Create<ITimeProvider>();
            Client clinet = new Client(timeProvider);
            Console.WriteLine(clinet.GetYear());
            Console.WriteLine(clinet.GetDatetime());