Code-C#-Delegate：委托（delegate）的三种调用方式：同步调用，异步调用，异步回调

using System;
using System.Threading;

namespace ConsoleApp
{
    class Program
    {
        static void Main()
        {
            Console.WriteLine("===== 同步调用 SyncInvokeTest =====");
            AddHandler handler = new AddHandler(加法类.Add);
            int result = handler.Invoke(1, 2);
            Console.WriteLine("继续做别的事情。。。");
            Console.WriteLine(result);
            Console.ReadKey();
        }
    }
    public delegate int AddHandler(int a, int b);
    public class 加法类
    {
        public static int Add(int a, int b)
        {
            Console.WriteLine("开始计算：" + a + "+" + b);
            Thread.Sleep(1000);
            Console.WriteLine("计算完成！");
            return a + b;
        }
    }
}

using System;
using System.Threading;

namespace ConsoleApp
{
    class Program
    {
        static void Main()
        {
            Console.WriteLine("===== 异步调用 AsyncInvokeTest =====");
            AddHandler handler = new AddHandler(加法类.Add);
            //IAsyncResult: 异步操作接口(interface)
            //BeginInvoke: 委托(delegate)的一个异步方法的开始
            IAsyncResult result = handler.BeginInvoke(1, 2, null, null);
            Console.WriteLine("继续做别的事情。。。");
            //异步操作返回
            Console.WriteLine(handler.EndInvoke(result));
            Console.ReadKey();
        }
    }

    public delegate int AddHandler(int a, int b);
    public class 加法类
    {
        public static int Add(int a, int b)
        {
            Console.WriteLine("开始计算：" + a + "+" + b);
            Thread.Sleep(1000);
            Console.WriteLine("计算完成！");
            return a + b;
        }
    }
}

using System;
using System.Runtime.Remoting.Messaging;
using System.Threading;

namespace ConsoleApp
{
    class Program
    {
        static void Main()
        {
            Console.WriteLine("===== 异步回调 AsyncInvokeTest =====");
            AddHandler handler = new AddHandler(加法类.Add); //异步操作接口(注意BeginInvoke方法的不同！)
            IAsyncResult result = handler.BeginInvoke(1, 2, new AsyncCallback(回调函数), "AsycState:OK");
            Console.WriteLine("继续做别的事情。。。");
            Console.ReadKey();
        }
        static void 回调函数(IAsyncResult result)
        {
            //result 是“加法类.Add()方法”的返回值
            //AsyncResult 是IAsyncResult接口的一个实现类，空间：System.Runtime.Remoting.Messaging
            //AsyncDelegate 属性可以强制转换为用户定义的委托的实际类。
            AddHandler handler = (AddHandler)((AsyncResult)result).AsyncDelegate;
            Console.WriteLine(handler.EndInvoke(result));
            Console.WriteLine(result.AsyncState);
        }
    }

    public delegate int AddHandler(int a, int b);
    public class 加法类
    {
        public static int Add(int a, int b)
        {
            Console.WriteLine("开始计算：" + a + "+" + b);
            Thread.Sleep(1000);
            Console.WriteLine("计算完成！");
            return a + b;
        }
    }
}