using System.Collections.Generic;
1.泛型引入
泛型方法：
1 /// <summary> 2 /// When You meet some the same things, especially on methods, you could use the generic. 3 /// </summary> 4 class TestGeneric 5 { 6 /// <summary> 7 /// obj method 8 /// </summary> 9 /// <param name="obj"></param> 10 public static void ShowObject(object obj) 11 { 12 Console.WriteLine("class is {0} , parameter = {1} , value = {2}", 13 typeof(TestGeneric).Name, obj.GetType().Name, obj); 14 } 15 /// <summary> 16 /// generic Method 17 /// from .net framework 2.0, updated CLR 18 /// delay for statement 19 /// </summary> 20 /// <typeparam name="T"></typeparam> 21 /// <param name="t"></param> 22 public static void ShowObject<T>(T t) 23 { 24 Console.WriteLine("class is {0} , parameter = {1} , value = {2}", 25 typeof(TestGeneric).Name, t.GetType().Name, t); 26 } 27 }
测试代码：
1 //int i = 5; 2 //float j = 2.0f; 3 //TestGeneric.ShowObject(i); 4 //TestGeneric.ShowObject<float>(j); 5 //TestGeneric.ShowObject(j);//Do not define the type, but it will auto-acculate the type from the parameter. 6 //Console.WriteLine(typeof(List<>)); 7 //Console.WriteLine(typeof(Dictionary<,>));
2.泛型类
1 /// <summary> 2 /// generic Class 3 /// </summary> 4 /// <typeparam name="T"></typeparam> 5 /// <typeparam name="Jungle"></typeparam> 6 public class GenericClass<T, Jungle> 7 { 8 public void Show(T t) 9 { 10 11 } 12 13 public Jungle Get() 14 { 15 return default(Jungle); 16 } 17 }
3.泛型接口
1 /// <summary> 2 /// generic Interface 3 /// </summary> 4 /// <typeparam name="T"></typeparam> 5 public interface IStudy<T> 6 { 7 void Study(); 8 T Study(T t); 9 }
4.泛型委托
1 /// <summary> 2 /// generic Delegate 3 /// </summary> 4 /// <typeparam name="EveryThing"></typeparam> 5 /// <returns></returns> 6 public delegate EveryThing GetHandler<EveryThing>();
5.泛型的继承
1 /// <summary> 2 /// Common Class 3 /// </summary> 4 public class Child 5 //: GenericClass<T, Jungle> //Common class cannot directly inherit the Generic Class 6 : GenericClass<int, string>, IStudy<string> // must be defined the type of inner, the same as the interface 7 { 8 public void Study() 9 { 10 throw new NotImplementedException(); 11 } 12 13 public string Study(string t) 14 { 15 throw new NotImplementedException(); 16 } 17 } 18 19 /// <summary> 20 /// GenericClass 21 /// </summary> 22 /// <typeparam name="T"></typeparam> 23 /// <typeparam name="Jungle"></typeparam> 24 public class GenericChild<T, Jungle> 25 : GenericClass<T, String>, IStudy<string> // But GenericClass can directly inherit the Generic Class, so the same as interface 26 { 27 public void Study() 28 { 29 throw new NotImplementedException(); 30 } 31 32 public string Study(string t) 33 { 34 throw new NotImplementedException(); 35 } 36 }
6.out and In
1 /// <summary> 2 /// 只能放在接口或者委托的泛型参数前面 3 /// out 协变covariant 修饰返回值 4 /// in 逆变contravariant 修饰传入参数 5 /// From C#-4.0 6 /// </summary> 7 public class InAndOut 8 { 9 #region Bird,Sparrow 10 public class Bird 11 { 12 public int Id { get; set; } 13 } 14 15 public class Sparrow : Bird 16 { 17 public string Name { get; set; } 18 } 19 #endregion 20 21 22 List<Bird> BirdList = new List<Bird>(); 23 //List<Bird> BirdList1 = new List<Sparrow>(); //Error CS0029 Cannot implicitly convert type List<Bird> to List<Sparrow>, because of non-inheritance, evev though the Sparrow is inherited from the Bird. 24 List<Bird> birdList2 = new List<Sparrow>().Select(c => (Bird)c).ToList();//You can try this method. 25 IEnumerable<Bird> BirdListOut = new List<Sparrow>();//the convert automatically by Compiler. 26 27 //out 协变covariant 修饰返回值 28 public interface ICustomerListOut<out T> 29 { 30 T Get();//只能作为返回值 31 } 32 public class CustomerListOut<T> : ICustomerListOut<T> 33 { 34 public T Get() 35 { 36 return default(T); 37 } 38 } 39 ICustomerListOut<Bird> customerListout1 = new CustomerListOut<Bird>(); 40 ICustomerListOut<Bird> customerListout2 = new CustomerListOut<Sparrow>();//Sparrow --> Bird 41 42 //in 逆变contravariant 修饰传入参数 43 public interface ICustomerListIn<in T>//只能放在接口或者委托的泛型参数前面 44 { 45 void Show(T t);//只能作为传入参数 46 } 47 public class CustomerListIn<T> : ICustomerListIn<T> 48 { 49 public void Show(T t) { Console.WriteLine("customized contravariant"); } 50 } 51 ICustomerListIn<Sparrow> customerListIn1 = new CustomerListIn<Sparrow>(); 52 ICustomerListIn<Sparrow> customerListIn2 = new CustomerListIn<Bird>();//Bird --> Sparrow 53 54 //in + out 55 public interface IMyList<in inT, out outT> 56 { 57 //out只能是返回值, in只能是参数. 58 void Show(inT t); 59 outT Get(); 60 outT Do(inT t); 61 } 62 public class MyList<T1, T2> : IMyList<T1, T2> 63 { 64 public void Show(T1 t) { Console.WriteLine(t.GetType().Name); } 65 public T2 Get() { 66 Console.WriteLine(typeof(T2).Name); 67 return default(T2); 68 } 69 public T2 Do(T1 t) 70 { 71 Console.WriteLine(t.GetType().Name); 72 return default(T2); 73 } 74 } 75 IMyList<Sparrow, Bird> myList1 = new MyList<Sparrow, Bird>();//正常情况 76 IMyList<Sparrow, Bird> myList2 = new MyList<Sparrow, Sparrow>();//协变-out 77 IMyList<Sparrow, Bird> myList3 = new MyList<Bird, Bird>();//逆变-in 78 IMyList<Sparrow, Bird> myList4 = new MyList<Bird, Sparrow>();//out+in 79 80 81 }
7. 泛型用于缓存
public class GenericCache { public static void Show() { for (int i = 0; i < 5; i++) { Console.WriteLine(DictionaryCache.GetCache<int>()); Thread.Sleep(10); Console.WriteLine(DictionaryCache.GetCache<long>()); Thread.Sleep(10); Console.WriteLine(DictionaryCache.GetCache<DateTime>()); Thread.Sleep(10); Console.WriteLine(DictionaryCache.GetCache<string>()); Thread.Sleep(10); Console.WriteLine(DictionaryCache.GetCache<GenericCache>()); Thread.Sleep(10); } for (int i = 0; i < 5; i++) { Console.WriteLine(GenericCache<int>.GetCache()); Thread.Sleep(10); Console.WriteLine(GenericCache<long>.GetCache()); Thread.Sleep(10); Console.WriteLine(GenericCache<DateTime>.GetCache()); Thread.Sleep(10); Console.WriteLine(GenericCache<string>.GetCache()); Thread.Sleep(10); Console.WriteLine(GenericCache<GenericCache>.GetCache()); Thread.Sleep(10); } } } /// <summary> /// 字典缓存：静态属性常驻内存 /// 若执行5次，则是一个类-Dictionary，5个值放入字典。 /// </summary> public class DictionaryCache { private static Dictionary<string, string> _TypeTimeDictionary = null; static DictionaryCache() { Console.WriteLine("DictionaryCache---静态构造函数!"); _TypeTimeDictionary = new Dictionary<string, string>(); } public static string GetCache<T>() { Type type = typeof(T); if (!_TypeTimeDictionary.ContainsKey(type.Name)) { _TypeTimeDictionary[type.Name] = string.Format("{0}_{1}", typeof(T).FullName, DateTime.Now.ToString()); } return _TypeTimeDictionary[type.Name]; } } /// <summary> /// 每个不同的T,都会生成一份不同的副本 /// 适合不同类型,需要缓存一份数据的场景,效率高 /// 若执行5次，则是5个类，5个值_TypeTime。 /// 缺陷：无法清除缓存 /// </summary> /// <typeparam name="T"></typeparam> public class GenericCache<T> { static GenericCache() { Console.WriteLine("DictionaryCache---静态构造函数!"); _TypeTime = string.Format("{0}_{1}", typeof(T).FullName, DateTime.Now.ToString("yyyyMMddHHmmss.fff")); } private static string _TypeTime = ""; public static string GetCache() { return _TypeTime; } }
