C event usage case subscription event+=

  C# Event usage

 

using System;

namespace WeiTuo
{
    class Program
    {
        // SayUpdate  Type of event .   The statement 1 Events . 
        public static event SayUpdate SayHelloEvent;
        //  Delegate with one parameter   And no return value of the delegate  
        public delegate void SayUpdate(string name);
        
        static void Main(string[] args)
        {
           

            //  Statement of delegation    How to use delegation    Interpretation of entrustment   Pass the method as a variable , And execute in the form of method . 
            // 



            SayUpdate dlg = SayHi;
            dlg += SayBye;
            dlg -= SayBye;

            //dlg(" voice , How do you do ");

            //  Anonymous functions  

            //  How to use events  +=  -=  1  use +=  Subscription events     Incidents 2 A way , One +=   One -= Method . 
            //  register   Subscription events .  
            SayHelloEvent += Program_SayHelloEvent;

            //  Judge whether the event exists . Not empty .
            if(SayHelloEvent != null)
            {
                SayHelloEvent(" Lao Wang "); //  Call event   
            }

            Console.ReadLine();


        }

        private static void Program_SayHelloEvent(string name)
        {
            //throw new NotImplementedException();
            Console.WriteLine($"{name}, I'm an event ！");
        }







        public static void SayHi(string name)
        {
            Console.WriteLine($"{ name}, How do you do   Speech technology ");
        }

        public static void SayBye(string name)
        {
            Console.WriteLine($"{ name}, bye ");
        }


    }
}

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