delegate event 以及lambda expression的基本例子(synchronous invocation)

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// C#代码 Car.cs

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using System;using System.Collections.Generic;

using System.Linq;

using System.Text;

 

namespace event_test

{

    class Car

    {

        private int speed;

        public Car(int speed)

        {

            this.speed = speed;

        }

        //delegate TYPE declaration(CarEventHandler is delegate of type "void(object,CarEventArgs)")

        public delegate void CarEventHandler(Object sender,CarEventArgs e);

        //event is syntactic sugar of defining internal private delegate object and providing add/remove functionality

        //i.e. define member variable of delegate type and (provide helper method to)add members to the invocation list

        //see 《Pro C# .NET3.5 Platform》Ebook pp.379

        public event CarEventHandler eventBusted;

        //defining event using generic EventHandler

        public event EventHandler<CarEventArgs> GenericEventBusted;

        public void accelerate(int delta)

        {

            if (speed+delta>100)

            {

                if (eventBusted!=null)

                {

                    eventBusted(this,new CarEventArgs(true,true));

                    GenericEventBusted(this, new CarEventArgs(true, true));

                }

            }

            else

            {

                speed += delta;

                Console.WriteLine("current speed is {0}", speed);

            }

        }

 

    }

}

 

public class CarEventArgs:EventArgs

{

    public readonly bool bCarBusted;

    public readonly bool bDriverAlive;

    public CarEventArgs(bool isCarBusted,bool isDriverAlive)

    {

        this.bCarBusted = isCarBusted;

        this.bDriverAlive = isDriverAlive;

    }

}

 

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//C#代码 Program.cs

////////////////////////////

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

 

namespace event_test

{

    class Program

    {

        static void Main(string[] args)

        {

            Car mycar = new Car(50);

            //EventObject calls InternalPrivateDelegateObject.Add() to add function to its invocation list

            mycar.eventBusted += new Car.CarEventHandler(ShowCarStatus);

            //using anonymous delegate

            mycar.eventBusted += delegate(object sender,CarEventArgs e)

            {

                Console.WriteLine("driver of car {0} is {1}", sender, e.bDriverAlive ? "alive" : "dead");

            };

            //using lambda expression(which is a shorthand for anonymous delegate)

            mycar.eventBusted += ((object sender, CarEventArgs e) => { Console.WriteLine("invoking lambda exp from {0}", sender); });

            //alternatively,we can use Generic delegate type: EventHandler

            mycar.GenericEventBusted += new EventHandler<CarEventArgs>(cbBustHandler);

            for (int i = 5; i >= 0;i--)

            {

                mycar.accelerate(15);

                Console.WriteLine();

            }

            Console.ReadLine();

        }

        //the (callback)function is defined here(stub is auto generated by intellisense when typing "someobject.event += new...")

        static void ShowCarStatus(object sender, CarEventArgs e)

        {

            Console.WriteLine("the car {0} is {1}",sender,(e.bCarBusted?"busted":"safe"));

        }

        static void cbBustHandler(object sender,EventArgs e)

        {

            Console.WriteLine("invoking from generic delegate type:EventHandler");

        }

    }

}