dotnet-event事件-使用笔记

事件event用于不同模块之间的通讯，本实例中，定义2个class，一个PublisherClass类申明了2个事件，2个方法，调用方法将会触发事件，通过股票代码code或者板块block查询股票信息。另一个SubscriberClass类，定义了一个List<Stock>成员用来保存股票Stock对象，2个方法注册给PublisherClass类对象的事件。

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

namespace EventDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Stock> stocks = new List<Stock>()
            {
                new Stock("002211", "长城科技", 11.1, "消费电子"),
                new Stock("300121", "桔子电子", 22.2, "消费电子"),
                new Stock("600006", "远东能源", 33.3, "能源板块"),
                new Stock("600101", "望城食品", 44.4, "食品板块")
            };

            // 实例化2个对象
            PublisherClass publisher = new PublisherClass();
            SubscriberClass subscriber = new SubscriberClass(stocks); 
            
            // 事件注册
            // 整个流程来看，要使用事件需申明委托、申明事件、注册事件、触发事件4个步骤
            publisher.GetInfoFromCodeEvent += subscriber.ReplyToInputCode;
            publisher.GetInfoFromBlockEvent += subscriber.ReplyToInputBlock;
            // 触发事件，输入代码查询股票信息
            publisher.GetInfoFromCode("300121");
            // 触发事件，输入板块查询股票信息
            publisher.GetInfoFromBlock("消费电子");

            Console.ReadLine();
        }
    }   

    // 委托申明
    public delegate void GetInfoFromCodeEventHandler(string code);
    public delegate void GetInfoFromBlockEventHandler(string block);

    // 事件发布者
    public class PublisherClass
    {
        // 事件申明，事件类型是委托类型
        public event GetInfoFromCodeEventHandler GetInfoFromCodeEvent;
        public event GetInfoFromBlockEventHandler GetInfoFromBlockEvent;

        public void GetInfoFromCode(string code)
        {
            GetInfoFromCodeEvent?.Invoke(code);
        }

        public void GetInfoFromBlock(string block)
        {
            GetInfoFromBlockEvent?.Invoke(block);
        }
    }

    /// <summary>
    /// SubscriberClass订阅者
    /// </summary>
    public class SubscriberClass
    {
        private List<Stock> _stocks;
        public SubscriberClass(List<Stock> list)
        {
            _stocks = list;
        }

        public void ReplyToInputCode(string code)
        {
            foreach(Stock stock in _stocks)
            {
                if(stock.code == code)
                    {
                        Console.WriteLine("Input stock: {0}\nName : {1}\nPrice : {2}\nBlock : {3}", stock.code, stock.name, stock.price, stock.block);
                    }
            }
        }
        public void ReplyToInputBlock(string block)
        {
            Console.WriteLine("------ Input Block : {0} ------", block);
            foreach (Stock stock in _stocks)
            {
                if (stock.block == block)
                {
                    string index = _stocks.IndexOf(stock).ToString();
                    Console.WriteLine("Index : {0}\nCode : {1}\nName : {2}\nPrice : {3}\n", index, stock.code, stock.name, stock.price);
                }
            }
        }
    }

    public class Stock
    {
        public string code;
        public string name;
        public double price;
        public string block; // 板块

        public Stock(string _code, string _name, double _price, string _block)
        {
            code = _code;
            name = _name;
            price = _price;
            block = _block;
        }
    }
}

如下代码，是在上面例子基础上增加一个AddStock功能。使用了dotnet自带的EventHandler事件代理，以及使用EventArgs类在模块之间传递事件信息。

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

namespace EventDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Stock> stocks = new List<Stock>()
            {
                new Stock("002211", "长城科技", 11.1, "消费电子"),
                new Stock("300121", "桔子电子", 22.2, "消费电子"),
                new Stock("600006", "远东能源", 33.3, "能源板块"),
                new Stock("600101", "望城食品", 44.4, "食品板块")
            };

            // 实例化2个对象
            PublisherClass publisher = new PublisherClass();
            SubscriberClass subscriber = new SubscriberClass(stocks); 
            
            // 事件注册
            // 整个流程来看，要使用事件需申明委托、申明事件、注册事件、触发事件4个步骤
            publisher.GetInfoFromCodeEvent += subscriber.ReplyToInputCode;
            publisher.GetInfoFromBlockEvent += subscriber.ReplyToInputBlock;
            publisher.AddStockEvent += subscriber.ReplyToAddStock;

            // 触发事件，输入代码查询股票信息
            publisher.GetInfoFromCode("300121");
            // 触发事件，输入板块查询股票信息
            publisher.GetInfoFromBlock("消费电子");
            // 触发事件，给股票列表新增一个Stock
            Stock stock = new Stock("300001", "大中华", 55, "国企改革");
            publisher.AddStock(stock);

            Console.ReadLine();
        }
    }   

    // 委托申明
    public delegate void GetInfoFromCodeEventHandler(string code);
    public delegate void GetInfoFromBlockEventHandler(string block);

    // 事件发布者
    public class PublisherClass
    {
        // 事件申明，事件类型是委托类型
        public event GetInfoFromCodeEventHandler GetInfoFromCodeEvent;
        public event GetInfoFromBlockEventHandler GetInfoFromBlockEvent;
        // 事件申明，使用内置EventHandler代理
        public event EventHandler<AddStockEventArgs> AddStockEvent;

        public void GetInfoFromCode(string code)
        {
            GetInfoFromCodeEvent?.Invoke(code);
        }

        public void GetInfoFromBlock(string block)
        {
            GetInfoFromBlockEvent?.Invoke(block);
        }
        
        public void AddStock(Stock stock)
        {
            AddStockEventArgs args = new AddStockEventArgs();
            args.stock = stock;
            //OnAddStockEvent(args);
            AddStockEvent?.Invoke(this, args);
        }

        // 也可以把AddStock()方法拆分成如下AddStock()和OnAddStockEvent()方法
        // 下面的方式是微软Example中的方式，具体描述可以参考文档
        //public void AddStock(Stock stock)
        //{
        //    AddStockEventArgs args = new AddStockEventArgs();
        //    args.stock = stock;
        //    OnAddStockEvent(args);
        //}

        // 为了继承类可以重写该函数，需声明为virtual虚函数，
        //protected virtual void OnAddStockEvent(AddStockEventArgs e)
        //{
        //    EventHandler<AddStockEventArgs> handler = AddStockEvent;
        //    handler(this, e);
        //}
    }

    // 继承EventArgs类，stock成员用于模块间传递
    public class AddStockEventArgs : EventArgs
    {
        public Stock stock;
    }

    /// <summary>
    /// SubscriberClass订阅者
    /// </summary>
    public class SubscriberClass
    {
        private List<Stock> _stocks;
        public SubscriberClass(List<Stock> list)
        {
            _stocks = list;
        }

        public void ReplyToInputCode(string code)
        {
            foreach(Stock stock in _stocks)
            {
                if(stock.code == code)
                    {
                        Console.WriteLine("Input stock: {0}\nName : {1}\nPrice : {2}\nBlock : {3}", stock.code, stock.name, stock.price, stock.block);
                    }
            }
        }
        public void ReplyToInputBlock(string block)
        {
            Console.WriteLine("------ Input Block : {0} ------", block);
            foreach (Stock stock in _stocks)
            {
                if (stock.block == block)
                {
                    string index = _stocks.IndexOf(stock).ToString();
                    Console.WriteLine("Index : {0}\nCode : {1}\nName : {2}\nPrice : {3}\n", index, stock.code, stock.name, stock.price);
                }
            }
        }
        public void ReplyToAddStock(object sender, AddStockEventArgs e)
        {
            _stocks.Add(e.stock);
            Console.WriteLine("------ 增加一条股票信息 从新显示 ------");
            Console.WriteLine("------ Stock List ------");
            foreach (Stock stock in _stocks)
            {
                string index = _stocks.IndexOf(stock).ToString();
                Console.WriteLine("Index : {0}\nCode : {1}\nName : {2}\nPrice : {3}\nBlock : {4}\n", index, stock.code, stock.name, stock.price, stock.block);
            }
        }
    }

    public class Stock
    {
        public string code;
        public string name;
        public double price;
        public string block; // 板块

        public Stock(string _code, string _name, double _price, string _block)
        {
            code = _code;
            name = _name;
            price = _price;
            block = _block;
        }
    }
}

参考文档：

https://docs.microsoft.com/en-us/dotnet/standard/events/

https://docs.microsoft.com/en-us/dotnet/api/system.eventhandler?view=net-6.0

https://docs.microsoft.com/en-us/dotnet/api/system.eventargs?view=net-6.0

https://blog.csdn.net/qq_27278957/article/details/86627861