Action委托

1. 无参无返回值

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            //1. 使用new关键字和调用Invoke方法
            Action action1 = new Action(ActionWithNoParaNoReturn);
            action1.Invoke();

            //2. 直接将方法名复制给Action委托，直接调用(推荐)
            Action action2 = ActionWithNoParaNoReturn;
            action2();

            //3. 匿名委托
            Action action3 = delegate() { Console.WriteLine("无参无返回值"); };
            action3();

            //4. Lambda委托(推荐)
            Action action4 = () => { Console.WriteLine("无参无返回值"); };
            action4();

            Console.ReadLine();
        }
        public static void ActionWithNoParaNoReturn()
        {
            Console.WriteLine("无参无返回值");
        }
    }
}

2. 单一参数无返回值

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            //1. 使用new关键字和调用Invoke方法
            Action<String> action1 = new Action<String>(ActionWithPara);
            action1.Invoke("test");

            //2. 直接将方法名复制给Action委托，直接调用(推荐)
            Action<String> action2 = ActionWithPara;
            action2("test");

            //3. 匿名委托
            Action<String> action3 = delegate(String value) { Console.WriteLine("这里是有参无返回值，参数值是：{0}", value); };
            action3("test");

            //4. Lambda委托(推荐)
            Action<String> action4 = (value) => { Console.WriteLine("这里是有参无返回值，参数值是：{0}", value); };
            action4("test");

            Console.ReadLine();
        }
        public static void ActionWithPara(String value)
        {
            Console.WriteLine("这里是有参无返回值，参数值是：{0}", value);
        }
    }
}

3. 多参数无返回值

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            //1. 使用new关键字和调用Invoke方法
            Action<String, int> action1 = new Action<String, int>(ActionWithMulitPara);
            action1.Invoke("test", 1);

            //2. 直接将方法名复制给Action委托，直接调用(推荐)
            Action<String, int> action2 = ActionWithMulitPara;
            action2("test", 1);

            //3. 匿名委托
            Action<String, int> action3 = delegate(String value1, int value2) { Console.WriteLine("这里有两个参数无返回值，参数值1是：{0}，参数值2是：{1}", value1, value2); };
            action3("test", 1);

            //4. Lambda委托(推荐)
            Action<String, int> action4 = (value1, value2) => { Console.WriteLine("这里有两个参数无返回值，参数值1是：{0}，参数值2是：{1}", value1, value2); };
            action4("test", 2);

            Console.ReadLine();
        }
        public static void ActionWithMulitPara(String value1, int value2)
        {
            Console.WriteLine("这里有两个参数无返回值，参数值1是：{0}，参数值2是：{1}", value1, value2);
        }
    }
}

4. 将委托当做参数值传递

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            Test<string, int>(Action, "Hello World!", 2);
            Test<string, int>((p, q) => { Console.WriteLine("值1：{0}, 值2：{1}", p, q); }, "Hello World", 2);//使用Lambda表达式定义委托
            Console.ReadKey();
        }

        public static void Test<T1, T2>(Action<T1, T2> action, T1 t1, T2 t2)
        {
            action(t1, t2);
        }

        private static void Action(string s, int i)
        {
            Console.WriteLine("值1：{0}, 值2：{1}", s, i);
        }
    }
}

5. 案例应用

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    public class Student
    {
        public String Name { get; set; }
        public int Id { get; set; }
        public int Age { get; set; }
        public int Sex { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            List<Student> list = new List<Student>()
            {
              new Student(){Id=1,Name="张三",Age=19,Sex=1},
              new Student(){Id=2,Name="李四",Age=20,Sex=2},
              new Student(){Id=3,Name="王五",Age=23,Sex=1},
              new Student(){Id=4,Name="赵六",Age=18,Sex=1}
            };

            //1. ForEach方法遍历
            Console.WriteLine("----ForEach方法遍历----");
            list.ForEach(p =>
            {
                Console.WriteLine("姓名：{0}, 年龄：{1}", p.Name, p.Age);
            });

            //2. foreach循环遍历
            Console.WriteLine("----foreach循环遍历----");
            foreach (var item in list)
            {
                Console.WriteLine("姓名：{0}, 年龄：{1}", item.Name, item.Age);
            }

            Console.ReadLine();
        }

    }
}