namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            Calculator calculator = new Calculator();

            // 委托方式一(方法是没有返回值的)
            //Report方法后面()
            Action action = new Action(calculator.Report);

            // 直接调用
            calculator.Report();

            // 间接调用
            action.Invoke();

            // 简写
            action();

            // 委托方式二(方法带参数)
            // 第一个int是返回值,第二第三是方法参数
            Func<int, int, int> func1 = new Func<int, int, int>(calculator.Add);
            Func<int, int, int> func2 = new Func<int, int, int>(calculator.Sub);

            int x = 100;
            int y = 200;
            int z = 0;

			// 方式1
           	z = func1(x, y);
            Console.WriteLine(z);
            // 方式2
            z = func2.Invoke(x, y);
            Console.WriteLine(z);
        }
    }

    class Calculator
    {
        public void Report()
        {
            Console.WriteLine("I have 3 methods");
        }

        public int Add(int a, int b)
        {
            int result = a + b;
            return result;
        }

        public int Sub(int a, int b)
        {
            int result = a - b;
            return result;
        }
    }
}

自定义委托

namespace ConsoleApp2
{
    // 声明委托,类型约束,返回值是double, 有两个double形参
    public delegate double Calc(double x, double y);

    class Program
    {
        static void Main(string[] args)
        {
            Calculator calculator = new Calculator();
            Calc calc1 = new Calc(calculator.Add);
            Calc calc2 = new Calc(calculator.Sub);
            Calc calc3 = new Calc(calculator.Mul);
            Calc calc4 = new Calc(calculator.Div);

            double a = 100;
            double b = 200;
            //double c = calc1.Invoke(a, b);

            Console.WriteLine(calc1(a,b));
            Console.WriteLine(calc2(a,b));
            Console.WriteLine(calc3(a,b));
            Console.WriteLine(calc4(a,b));
        }
    }

    class Calculator
    {
        public void Report()
        {
            Console.WriteLine("I have 3 methods");
        }

        public double Add(double a, double b)
        {
            double result = a + b;
            return result;
        }

        public double Sub(double a, double b)
        {
            double result = a - b;
            return result;
        }

        public double Mul(double a, double b)
        {
            double result = a * b;
            return result;
        }

        public double Div(double a, double b)
        {
            double result = a / b;
            return result;
        }
    }
}

委托的一般使用

实例: 把方法当作参数传递给另一个方法

模板方法

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            ProductFactory productFactory = new ProductFactory();
            WrapFactory wrapFactory = new WrapFactory();

			// 返回值是Product
            Func<Product> fun1 = new Func<Product>(productFactory.MakePizza);
            Func<Product> fun2 = new Func<Product>(productFactory.MakeToyCar);

            Box box1 = wrapFactory.WrapProduct(fun1);
            Console.WriteLine(box1.Product.Name);

            Box box2 = wrapFactory.WrapProduct(fun2);
            Console.WriteLine(box2.Product.Name);
        }
    }

    class Product
    {
        public string Name { get; set; }
    }

    class Box
    {
        public Product Product { get; set; }
    }

    class WrapFactory
    {
        public Box WrapProduct(Func<Product> getProduct)
        {
            Box box = new Box();
            Product product = getProduct.Invoke();
            box.Product = product;
            return box;
        }
    }

    class ProductFactory
    {
        public Product MakePizza()
        {
            Product product = new Product();
            product.Name = "Pizza";
            return product;
        }

        public Product MakeToyCar()
        {
            Product product = new Product();
            product.Name = "Toy Car";
            return product;
        }
    }
}

回调方法

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            ProductFactory productFactory = new ProductFactory();
            WrapFactory wrapFactory = new WrapFactory();

			// 返回值是Product
            Func<Product> fun1 = new Func<Product>(productFactory.MakePizza);
            Func<Product> fun2 = new Func<Product>(productFactory.MakeToyCar);

            Logger logger = new Logger();
            // 参数是Product
            // 封装只有一个参数且不返回值的方法。
            Action<Product> action1 = new Action<Product>(logger.Log);



            Box box1 = wrapFactory.WrapProduct(fun1, action1);
            Console.WriteLine(box1.Product.Name);

            Box box2 = wrapFactory.WrapProduct(fun2, action1);
            Console.WriteLine(box2.Product.Name);
        }
    }

    class Product
    {
        public string Name { get; set; }
        public double Price { get; set; }

    }

    class Logger
    {
        public void Log(Product product)
        {
            Console.WriteLine($"Product '{product.Name}' areate at {DateTime.UtcNow}. Price is {product.Price}");
        }
    }

    class Box
    {
        public Product Product { get; set; }
    }

    class WrapFactory
    {
        public Box WrapProduct(Func<Product> getProduct, Action<Product> logCallback)
        {
            Box box = new Box();
            Product product = getProduct.Invoke();

            if (product.Price >= 50)
            {
                logCallback(product);
            }

            box.Product = product;
            return box;
        }
    }

    class ProductFactory
    {
        public Product MakePizza()
        {
            Product product = new Product();
            product.Name = "Pizza";
            product.Price = 12;
            return product;
        }

        public Product MakeToyCar()
        {
            Product product = new Product();
            product.Name = "Toy Car";
            product.Price = 100;
            return product;
        }
    }
}