委托

01.委托作为方法传递

using System;
using static System.Console;

namespace Mydelegate1
{
    //委托声明
    public delegate bool ComparsionHandler(int first,int second);
    class Program
    {
        static void Main(string[] args)
        {
            int[] sum = new[] {5, 10, 2, 0, 40, 6, 9, 8};

            BubbleSort(sum, GreaterThan);
            foreach (var item in sum)
            {
                WriteLine(item);
            }
            ReadKey();
        }

        //委托作为方法传递
        public static void BubbleSort(int[] items,ComparsionHandler comparsionMethod)
        {
            int i  ;
            int j ;
            int temp;

            for (i = items.Length - 1; i >=0; i--)
            {
                for (j = 1; j <=i ; j++)
                {
                    if (comparsionMethod(items[j-1],items[j]))
                    {
                        temp = items[j - 1];
                        items[j - 1] = items[j];
                        items[j] = temp;
                    }
                }
            }
        }

        public static bool GreaterThan(int first, int second)
        {
            return first > second;

        }
    }

}

02.

03.Lambda表达式

//委托声明
    public delegate bool ComparsionHandler(int first, int second);
    class Program
    {
        static void Main(string[] args)
        {

            int[] sum = new[] { 5, 10, 2, 0, 40, 6, 9, 8 };
            //整数 first和整数 second 用于 返回 first大于second的结果
            BubbleSort(sum, (int first, int second) => { return first >second;});
            //BubbleSort(sum, (int first, int second) => first > second);
            foreach (var item in sum)
            {
                WriteLine(item);
            }

            ReadKey();
        }


        //委托作为方法传递
        public static void BubbleSort(int[] items, ComparsionHandler comparsionMethod)
        {
            int i;
            int j;
            int temp;

            for (i = items.Length - 1; i >= 0; i--)
            {
                for (j = 1; j <= i; j++)
                {
                    if (comparsionMethod(items[j - 1], items[j]))
                    {
                        temp = items[j - 1];
                        items[j - 1] = items[j];
                        items[j] = temp;
                    }
                }
            }
        }

    }

04.通用的委托

namespace Mydelegate5
{
    public delegate void Action<T>(T arg);
    
    class Program
    {
        public Func<int,float> func;
        static void Main(string[] args)
        {
            Program p=new Program();
            p.func = Sum;
            WriteLine(p.func(10)); //10
            ReadKey();
        }

        static float Sum(int a)
        {
            return a;
        }
    }
}

05.多播委托

和空值传播运算符

using System;
using static System.Console;
namespace Event02
{
    class Program
    {
        static void Main(string[] args)
        {
            Thermostat thermostat=new Thermostat();
            Cooler cooler=new Cooler(60);
            Heater heater=new Heater(80);
            
            thermostat.OnTemperatureChanged += cooler.OnTemperatureChanged;
            thermostat.OnTemperatureChanged += heater.OnTemperatureChanged;
            while (true)
            {
                thermostat.CurrentTemperature = float.Parse(ReadLine());
            }
            
            ReadKey();
        }
    }

    //发布者
    class  Thermostat
    {
        public Action<float> OnTemperatureChanged { get; set;}
        private float _CurrentTemperature;

        public float CurrentTemperature
        {
            get => _CurrentTemperature;
            set
            {
                if (value!=CurrentTemperature)
                {
                    _CurrentTemperature = value;
                    OnTemperatureChanged?.Invoke(value);
                }
            } 
        }
    }


    //加热器
    class Cooler
    {
        public float Temperature { get; set; } //温度
        public Cooler(float temperature)
        {
            this.Temperature = temperature;
        }

        public void OnTemperatureChanged(float newTemperature)
        {
            if (newTemperature>Temperature)
            {
                WriteLine("Cooler:ON");
            }
            else
            {
                WriteLine("Cooler:Off");
            }
        }
    }

    //冷却器
    class Heater
    {
        public float Temperature { get; set; } //温度
        public Heater(float temperature)
        {
            this.Temperature = temperature;
        }
        public void OnTemperatureChanged(float newTemperature)
        {
            if (newTemperature <Temperature)
            {
                WriteLine("Heater:ON");
            }
            else
            {
                WriteLine("Heater:Off");
            }
        }
    }
}