委托学习小案例二

委托学习小案例二

 

    /// <summary>
    /// 泛型、委托、事件
    /// </summary>
    class Program
    {
        //1.声明委托
        public delegate void SaySomething(string name);  
        private delegate double DoCallFunc(double num1, double num2);

        //2.声明事件
        public static event SaySomething peopleCome; // 关注SaySomething委托，当事件发生的时候，会通知关注的“委托”（再由这些“委托”去调用具体的方法）。

      
        #region 普通委托
        private static double Calculate2(double num1, double num2, DoCallFunc doCallFunc)
        {
            return doCallFunc(num1, num2);
        }
        #endregion

        #region 泛型委托

        /*
            泛型Action<T>委托表示引用一个void返回类型的方法。Action<T>委托类存在不同的变体，可以传递至多16种不同的参数类型，
            没有泛型参数的Action类可以调用没有参数的方法。
            例如：Action<in T1>调用带一个参数的方法，Action<in T1,in T2>调用带两个参数的方法等
    　　    
            Func<T>的用法和Action<T>用法类似，但是Func<T>表示引用一个带返回类型的方法，
            Func<T>也存在不同的变体，至多可以传递16个参数类型和1个返回类型，
            例如：Func<in T1,out Resout>表示带一个参数的方法，Func<in T1,in T2,out Resout>表示调用带两个参数的方法。
        */

        //3.利用Func<T>定义委托方法
        private static double Calculate(double num1, double num2, Func<double, double, double> callFunc)
        {
            return callFunc(num1, num2);
        }
        #endregion

        #region 数字的加减乘除
        //4.定义委托引用的方法
        //加
        private static double Add(double num1, double num2)
        {
            Console.WriteLine("{0} + {1} = {2}", num1, num2, num1 + num2);
            return num1 + num2;
        }
        //减
        private static double Sub(double num1, double num2)
        {
            Console.WriteLine("{0} - {1} = {2}", num1, num2, num1 - num2);
            return num1 - num2;
        }
        //乘
        private static double Multiply(double num1, double num2)
        {
            Console.WriteLine("{0} * {1} = {2}", num1, num2, num1 * num2);
            return num1 * num2;
        }
        //除
        private static double Divide(double num1, double num2)
        {
            Console.WriteLine("{0} / {1} = {2}", num1, num2, num1 / num2);
            return Math.Round(num1 / num2, 2, MidpointRounding.AwayFromZero);  //4舍5入
        }
        #endregion

        #region 测试
        //定义委托引用方法
        public static void SayHello(string name) { Console.WriteLine("Hello," + name + "!"); }

        public static void SayNiceToMeetYou(string name) { Console.WriteLine("Nice to meet you," + name + "!"); }

        public static void SayGoodbye(string name) { Console.WriteLine("Bye bye," + name + "!"); }
        #endregion


        static void Main(string[] args)
        {
            peopleCome += SayHello;  //注册方法到事件上
            peopleCome += SayNiceToMeetYou; //注册方法到事件上
            peopleCome += SayGoodbye; //注册方法到事件上
            peopleCome("Jerry");  //绑定触发事件

            Console.WriteLine("=====================================");

            int x = 4;
            int y = 3;
            // DoCallFunc md = new DoCallFunc(Add);

            DoCallFunc df;
            //引用委托方法Add
            df = Add;
            Console.WriteLine("callFunc：{0}", df(x, y));
            df = Sub;
            Console.WriteLine("callFunc：{0}", df(x, y));
            df = Multiply;
            Console.WriteLine("callFunc：{0}", df(x, y));
            df = Divide;
            Console.WriteLine("callFunc：{0}", df(x, y));

            //委托引用方法调用
            Console.WriteLine("=====================================");
            Console.WriteLine("callFunc：{0}", Calculate(x, y, Add));//引用委托方法Add
            Console.WriteLine("callFunc：{0}", Calculate(x, y, Sub));
            Console.WriteLine("callFunc：{0}", Calculate(x, y, Multiply));
            Console.WriteLine("callFunc：{0}", Calculate(x, y, Divide));

            Console.ReadKey();
        }

    }