コード例 #1
0
ファイル: Program.cs プロジェクト: junchenglai/csharp
        /// <summary>
        /// 1 引入泛型:延迟声明
        /// 2 如何声明和使用泛型
        /// 3 泛型的好处和原理
        /// 4 泛型类、泛型方法、泛型接口、泛型委托
        /// 5 泛型约束
        /// 6 协变、逆变
        /// 7 泛型缓存
        /// </summary>
        static void Main(string[] args)
        {
            try
            {
                int      iValue  = 123;
                string   sValue  = "456";
                DateTime dtValue = DateTime.Now;
                object   oValue  = "789";

                Console.WriteLine("*************** Common *****************");
                CommonMethod.ShowInt(iValue);
                CommonMethod.ShowString(sValue);
                CommonMethod.ShowDateTime(dtValue);

                Console.WriteLine("*************** Object *****************");
                CommonMethod.ShowObject(iValue);
                CommonMethod.ShowObject(sValue);
                CommonMethod.ShowObject(dtValue);
                CommonMethod.ShowObject(oValue);

                Console.WriteLine("*************** Generic ****************");
                CommonMethod.Show <int>(iValue); // 调用泛型,需要指定类型参数
                CommonMethod.Show(iValue);       // 如果可以从参数类型推断,可以省略类型参数
                CommonMethod.Show <string>(sValue);
                CommonMethod.Show <DateTime>(dtValue);
                CommonMethod.Show <object>(oValue);

                Console.WriteLine("************** 泛型原理 *****************");
                // 泛型是 .net framework 2.0 推出的,是框架升级的产物
                // 支持基础:
                // 1. 编译器支持类型参数,用占位符表示的
                // 2. CLR升级 CLR 2.0 (.net framework 2.0 - 4.0),运行时类型确定后再替换占位符
                Console.WriteLine(typeof(List <>));
                Console.WriteLine(typeof(Dictionary <,>));

                Console.WriteLine("************** Monitor *****************");
                // 泛型方法的性能与普通方法大致一致,是最好的
                // 可以一个方法满足多个不同的类型
                // object 装箱拆箱过程消耗大量性能
                Monitor.Show();

                Console.WriteLine("*********** GenericCache ***************");
                GenericCacheTest.Show();

                Console.WriteLine("******** GenericConstraint *************");
                People people = new People()
                {
                    Id = 001, Name = "Jone"
                };
                Chinese chinese = new Chinese()
                {
                    Id = 002, Name = "Mike"
                };
                Hubei hubei = new Hubei()
                {
                    Id = 003, Name = "Mirry"
                };
                Japanese japanese = new Japanese()
                {
                    Id = 004, Name = "Jakey"
                };

                GenericConstraint.ShowObject(people);
                GenericConstraint.ShowObject(chinese);
                GenericConstraint.ShowObject(hubei);
                // error: 编译通过,运行时报错
                // 没有约束,任何类型都能传递进来,所以不安全
                // GenericConstraint.ShowObject(japanese);

                GenericConstraint.Show(people);
                GenericConstraint.Show(chinese);
                GenericConstraint.Show(hubei);
                // error: 编译不通过
                // GenericConstraint.Show(Japanese);

                Console.WriteLine("******** 协变、逆变 *************");
                CCTest.Show();
            }
            catch (Exception)
            {
                throw;
            }
        }
コード例 #2
0
        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine(typeof(List <>));        //`1 占位符 1个参数
                Console.WriteLine(typeof(Dictionary <,>)); //`2

                int iValue = 123;
                // var iValue = 123;
                string   sValue  = "456";
                DateTime dtValue = DateTime.Now;
                object   oValue  = "Jonty";

                Console.WriteLine("*************************");
                CommonMethod.ShowInt(iValue);
                CommonMethod.ShowString(sValue);
                CommonMethod.ShowDateTime(dtValue);
                CommonMethod.ShowObject(oValue);

                // 全部用ShowObject
                CommonMethod.ShowObject(sValue);
                CommonMethod.ShowObject(iValue);
                CommonMethod.ShowObject(dtValue);

                Console.WriteLine("************Generic***********");
                GenericMethod.Show <int>(iValue);
                // 可省略 自动推断
                GenericMethod.Show(sValue);
                GenericMethod.Show <DateTime>(dtValue);

                Console.WriteLine("*************Monitor************");
                // common~=generic > object
                Monitor.Show();

                Generic <int> generic = new Generic <int>()
                {
                    _t = 123
                };


                {
                    People people = new People()
                    {
                        Id   = 12,
                        Name = "走自己的路"
                    };
                    Chinese chinese = new Chinese()
                    {
                        Id   = 34,
                        Name = "Jonty"
                    };
                    HuNan huNan = new HuNan()
                    {
                        Id   = 45,
                        Name = "长沙"
                    };
                    Japanese japanese = new Japanese()
                    {
                        Id   = 56,
                        Name = "波多"
                    };

                    CommonMethod.ShowObject(people);
                    CommonMethod.ShowObject(chinese);
                    CommonMethod.ShowObject(huNan);
                    CommonMethod.ShowObject(japanese);

                    GenericMethod.Show(people);
                    GenericMethod.Show(chinese);
                    GenericMethod.Show(huNan);
                    GenericMethod.Show(japanese);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                throw;
            }
        }