/// <summary>     /// 工厂接口定义     /// </summary>     /// <remarks>     ///     TTarget : abstract product type     ///     TSource:  concrete product type     /// </remarks>     public interface IFactory     {         #region config and register type mapping         /// <summary>         /// 如果需要同时加载配置文件中定义的映射关系，可以按照SRP的原则定义独立的配置类型。         /// 由该配置类型调用这两个接口为Factory加载配置信息         /// </summary>         IFactory RegisterType<TTarget, TSource>();  // fluent interface         IFactory RegisterType<TTarget, TSource>(string name);   // fluent interface         #endregion         #region factory method         TTarget Create<TTarget>();         TTarget Create<TTarget>(string name);         #endregion     }

public sealed class TypeRegistry     {         readonly string DefaultNmae = Guid.NewGuid().ToString();         IDictionary<Type, IDictionary<string, Type>> registry = new Dictionary<Type, IDictionary<string, Type>>();         public void RegisterType(Type targetType,Type sourceType)         {             RegisterType(targetType, sourceType, DefaultNmae);         }         public void RegisterType(Type targetType, Type sourceType,string name)         {             if (targetType == null) throw new ArgumentNullException("targetType");             if (sourceType == null) throw new ArgumentNullException("sourceType");             if (string.IsNullOrEmpty(name)) throw new ArgumentNullException("name");             IDictionary<string, Type> subDictionary;             if (!registry.TryGetValue(targetType, out subDictionary))             {                 subDictionary = new Dictionary<string, Type>();                 subDictionary.Add(name, sourceType);                 registry.Add(targetType, subDictionary);             }             else             {                 if (subDictionary.ContainsKey(name))                     throw new DuplicateKeyException(name);                 subDictionary.Add(name, sourceType);             }         }         public Type this[Type targetType, string name]         {             get             {                 if (targetType == null) throw new ArgumentNullException("targetType");                 if (string.IsNullOrEmpty(name)) throw new ArgumentNullException("name");                 if (registry.Count() == 0)                     return null;                 return (registry                     .Where(x => x.Key == targetType)).FirstOrDefault().Value                     .Where(x => string.Equals(name, x.Key))                         .FirstOrDefault().Value;             }         }         public Type this[Type targetType]         {             get { return this[targetType, DefaultNmae]; }         }     }

public class Factory : IFactory     {         protected TypeRegistry registry = new TypeRegistry();         #region IFactory Members         public IFactory RegisterType<TTarget, TSource>()         {             registry.RegisterType(typeof(TTarget), typeof(TSource));             return this;         }         public IFactory RegisterType<TTarget, TSource>(string name)         {             registry.RegisterType(typeof(TTarget), typeof(TSource), name);             return this;         }         public TTarget Create<TTarget>()         {             return (TTarget)Activator.CreateInstance(registry[typeof(TTarget)]);         }         public TTarget Create<TTarget>(string name)         {             return (TTarget)Activator.CreateInstance(registry[typeof(TTarget), name]);         }         #endregion     }

[TestMethod]         public void CreateInstance()         {             var factory = new Factory()                 .RegisterType<IFruit, Apple>()                 .RegisterType<IFruit, Orange>("o")                 .RegisterType<IVehicle, Bicycle>()                 .RegisterType<IVehicle, Bicycle>("a")                 .RegisterType<IVehicle, Train>("b")                 .RegisterType<IVehicle, Car>("c");             Assert.IsInstanceOfType(factory.Create<IFruit>(), typeof(Apple));             Assert.IsInstanceOfType(factory.Create<IFruit>("o"), typeof (Orange));             Assert.IsInstanceOfType(factory.Create<IVehicle>(), typeof(Bicycle));             Assert.IsInstanceOfType(factory.Create<IVehicle>("a"), typeof(Bicycle));             Assert.IsInstanceOfType(factory.Create<IVehicle>("b"), typeof(Train));             Assert.IsInstanceOfType(factory.Create<IVehicle>("c"), typeof(Car));         }