C#事件的原理和用法整理

    class Program
    {
        static void Main(string[] args)
        {
            Timer timer = new Timer();//timer是事件拥有者
            timer.Interval = 1000;
            Boy boy = new Boy();//boy是事件响应者
            timer.Elapsed += boy.Action; //Elapsed是事件 +=是订阅
            timer.Start();
            Console.ReadKey();
        }
    }

    public class Boy
    {
        //事件处理器
        internal void Action(object sender, ElapsedEventArgs e)
        {
            Console.WriteLine("hello");
        }
    }

namespace EventExample
{
    class Program
    {
        static void Main(string[] args)
        {
            Form form = new Form();
            Controller controller = new Controller(form);
            form.ShowDialog();
        }
    }

    class Controller
    {
        private Form form;
        public Controller(Form form)
        {
            if (form != null)
            {
                this.form = form;
                this.form.Click += this.Clicked;
            }
        }

        private void Clicked(object sender, EventArgs e)
        {
            this.form.Text = DateTime.Now.ToString();
        }
    }
}

namespace EventExample
{
    class Program
    {
        static void Main(string[] args)
        {
            MyForm myForm = new MyForm();
            myForm.ShowDialog();
        }
    }

    class MyForm : Form
    {
        private TextBox TextBox;
        private Button button;
        public MyForm()
        {
            this.TextBox = new TextBox();
            this.button = new Button();
            this.Controls.Add(this.button);
            this.Controls.Add(this.TextBox);
            this.button.Click += this.ButtonClicked;
            this.button.Text = "Click";
            this.button.Top = 50;
        }

        private void ButtonClicked(object sender, EventArgs e)
        {
            this.TextBox.Text = "Hello World!!!!!!!!!!!!";
        }
    }
}

namespace EventExample
{
    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();
            Waiter waiter = new Waiter();

            customer.Order += waiter.Action;//挂接事件。waiter的Action订阅着customer的Order
            customer.Action();
            customer.PayTheBill();
        }
    }

    public delegate void OrderEventHandler(Customer customer, OrderEventArgs e);//声明一个委托类型，专门用来声明事件，约束事件处理器


    public class OrderEventArgs : EventArgs//声明用来传递消息的类，派生自EventArgs
    {

        public string DishName { get; set; }
        public string Size { get; set; }
    }


    public class Customer //事件发起者
    {
        public event OrderEventHandler Order;//声明事件Order。用OrderEventHandler来约束事件
        
        public double Bill { get; set; }

        public void Walkin()
        {
            Console.WriteLine("Walk in the restaurant");
        }

        public void Sitdown()
        {
            Console.WriteLine("Sit down");
        }

        public void Think()
        {
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine("Let me think......");
                Thread.Sleep(1000);
            }

            if (this.Order != null)//等于空说明没有人订阅这个事件，会报异常
            {
                OrderEventArgs e = new OrderEventArgs();
                e.DishName = "Kongpao Chicken";
                e.Size = "large";
                this.Order.Invoke(this, e);
            }
        }

        public void Action()
        {
            Console.ReadLine();
            Walkin();
            Sitdown();
            Think();
        }
        
        public void PayTheBill()
        {
            Console.WriteLine("I Will pay ${0}.",this.Bill);
        }
    }

    public class Waiter  //事件的响应者Waiter
    {
        public void Action(Customer customer, OrderEventArgs e)//事件处理器
        {
            Console.WriteLine("I will serve you the dish - {0}", e.DishName);
            double price = 10;
            switch (e.Size)
            {
                case "small":
                    price = price * 0.5;
                    break;
                case "large":
                    price = price * 1.5;
                    break;
                default:
                    break;
            }
            customer.Bill += price;
        }
    }
}