构造注入

这种方式就是在构造函数时候注入类型

直接看例子

 public interface ITimeProvider
    {
        DateTime CurrentDate { get; }
    }

    public class TimeProvider : ITimeProvider
    {
        public DateTime CurrentDate { get { return DateTime.Now; } }
    }

    public class Assembler
    {
        static Dictionary<Type, Type> dictionary = new Dictionary<Type, Type>();
        static Assembler()
        {
            dictionary.Add(typeof(ITimeProvider), typeof(TimeProvider));
        }

        public object Creat(Type type)
        {
            if ((type == null) || !dictionary.ContainsKey(type))
                throw new NullReferenceException();
            return Activator.CreateInstance(dictionary[type]);
        }

        //泛型方式调用
        public T Creat<T>()
        {
            return (T)Creat(typeof(T));
        }
    }

下面看构造注入类

 public class Client
    {
        ITimeProvider timeProvider;
        public Client(ITimeProvider timeProvider)
        {
            this.timeProvider = timeProvider;
        }
    }

那么客户端调用时候

        [TestMethod()]
        public void ClientConstructorTest()
        {
            ITimeProvider timeProvider = (new Assembler()).Creat<ITimeProvider>();
            Assert.IsNotNull(timeProvider);
            Client target = new Client(timeProvider);
        }

这样又一次依赖Assembler达到客户端调用时候无需知道具体类型