委托异步调用

异步调用：

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

namespace ConsoleApplication49
{
    class Program
    {
        public delegate int AddHandler(int a, int b);  
        static void Main()
        {
            Console.WriteLine("**********AsyncInvokeTest**************");
            AddHandler handler = new AddHandler(Add);
            IAsyncResult result = handler.BeginInvoke(1, 2, null, null);
            Console.WriteLine("Do other work1... ... ...");
            Console.WriteLine(handler.EndInvoke(result));
            Console.WriteLine("Do other work2... ... ...");
            Console.ReadLine();
        }
        static int Add(int a, int b)
        {
            Console.WriteLine("Computing " + a + " + " + b + " ...");
            Thread.Sleep(3000);
            Console.WriteLine("Computing Complete.");
            return a + b;
        }  
    }
}

运行结果：

**********AsyncInvokeTest**************
Do other work1... ... ...
Computing 1 + 2 ...
Computing Complete.
3 

Do other work2... ... ...

 

 

可以看到，主线程并没有等待，而是直接向下运行了。
　　但是问题依然存在，当主线程运行到EndInvoke时，如果这时调用没有结束（这种情况很可能出现），这时为了等待调用结果，线程依旧会被阻塞。
　　解决的办法是用回调函数，当调用结束时会自动调用回调函数

回调异步：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Remoting.Messaging;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApplication49
{
    class Program
    {
        public delegate int AddHandler(int a, int b);
        static void Main()
        {
            Console.WriteLine("**********AsyncInvokeTest**************");
            AddHandler handler = new AddHandler(Add);
            IAsyncResult result = handler.BeginInvoke(1, 2, new AsyncCallback(AddComplete),
          "AsycState:OK");
            Console.WriteLine("Do other work ... ... ...");
            Console.ReadLine();
        }
        static int Add(int a, int b)
        {
            Console.WriteLine("Computing " + a + " + " + b + " ...");
            Thread.Sleep(3000);
            Console.WriteLine("Computing Complete.");
            return a + b;
        }
        static void AddComplete(IAsyncResult result)
        {
            AddHandler handler = (AddHandler)((AsyncResult)result).AsyncDelegate;
            Console.WriteLine(handler.EndInvoke(result));
            Console.WriteLine(result.AsyncState);
        }
    }
}

运行结果：

**********AsyncInvokeTest**************
Do other work... ... ...
Computing 1 + 2 ...
Computing Complete.
3 

AsycState:OK