使用异步方式调用同步方法(实例详解)

using System;
using System.Threading;
namespace AsyncTest
{
    public class AsyncDemo
    {
        //方法一
        public string TestMethod(int callDuration, out int threadId)
        {
            Console.WriteLine("Test method begins.");
            Thread.Sleep(callDuration);
            threadId = Thread.CurrentThread.ManagedThreadId;
            return String.Format("My call time was {0}.", callDuration.ToString());
        }
//方法二
public float Addxy(float x, float y)
        {
            return x * y;
        }
    }
    //定义两个对应于方法的委托，参数同方法一致,委托的声明写在调用类里也是一样的，不限
    public delegate string AsyncMethodCaller(int callDuration, out int threadId);
    public delegate float AsyncMethodCaller2(float x, float y);
}

using System;
using System.Threading;
namespace AsyncTest
{
    public class AsyncMain
    {
        public static void Main()
        {
            // The asynchronous method puts the thread id here.
            int threadId;
            //实例化.
            AsyncDemo ad = new AsyncDemo();
            // 定义委托
            AsyncMethodCaller caller = new AsyncMethodCaller(ad.TestMethod);

            //通过委托调用方法，回调函数为null
            IAsyncResult result = caller.BeginInvoke(3000,
                out threadId, null, null);

            Thread.Sleep(0);
            Console.WriteLine("Main thread {0} does some work.",
                Thread.CurrentThread.ManagedThreadId);

            // Call EndInvoke to wait for the asynchronous call to complete,会阻塞
            // and to retrieve the results.
            string returnValue = caller.EndInvoke(out threadId, result);

            Console.WriteLine("The call executed on thread {0}, with return value \"{1}\".",
                threadId, returnValue);
        }
    }
}

using System;
using System.Threading;
namespace AsyncTest
{
    public class AsyncMain
    {
        static void Main()
        {
            // The asynchronous method puts the thread id here.
            int threadId;
            //实例化
            AsyncDemo ad = new AsyncDemo();

            //定义委托.
            AsyncMethodCaller caller = new AsyncMethodCaller(ad.TestMethod);

            //调用
            IAsyncResult result = caller.BeginInvoke(3000,
                out threadId, null, null);

            Thread.Sleep(0);
            Console.WriteLine("Main thread {0} does some work.",
                Thread.CurrentThread.ManagedThreadId);

            // Wait for the WaitHandle to become signaled.
            result.AsyncWaitHandle.WaitOne();

            // Perform additional processing here.
            // Call EndInvoke to retrieve the results.
            string returnValue = caller.EndInvoke(out threadId, result);

            // Close the wait handle.
            result.AsyncWaitHandle.Close();

            Console.WriteLine("The call executed on thread {0}, with return value \"{1}\".",
                threadId, returnValue);
        }
    }
}

using System;
using System.Threading;
namespace AsyncTest
{
    public class AsyncMain
    {
        static void Main() {
            // The asynchronous method puts the thread id here.
            int threadId;

            //实例化.
            AsyncDemo ad = new AsyncDemo();

            //声明委托
            AsyncMethodCaller caller = new AsyncMethodCaller(ad.TestMethod);

            //调用.
            IAsyncResult result = caller.BeginInvoke(3000,
                out threadId, null, null);

            //轮询.
            while(result.IsCompleted == false) {
                Thread.Sleep(250);
                Console.Write(".");
            }
            //取结果.
            string returnValue = caller.EndInvoke(out threadId, result);

            Console.WriteLine("\nThe call executed on thread {0}, with return value \"{1}\".",
                threadId, returnValue);
        }
    }
}

using System;
using System.Threading;
using System.Runtime.Remoting.Messaging;
namespace AsyncTest
{
    public class AsyncMain
    {
        static void Main()
        {
            //实例化类.
            AsyncDemo ad = new AsyncDemo();

            //实例两个不同的委托，分别对应不同的方法.
            AsyncMethodCaller caller = new AsyncMethodCaller(ad.TestMethod);

AsyncMethodCaller2 caller2 = new AsyncMethodCaller2(ad.Addxy);

            // The threadId parameter of TestMethod is an out parameter, so
            // its input value is never used by TestMethod. Therefore, a dummy
            // variable can be passed to the BeginInvoke call. If the threadId
            // parameter were a ref parameter, it would have to be a class-
            // level field so that it could be passed to both BeginInvoke and
            // EndInvoke.
            int dummy = 0;

            // 调用时指定回调方法，在异步执行完后会自动调用该方法，用来取得执行的结果
            IAsyncResult result = caller.BeginInvoke(3000,
                out dummy,
                new AsyncCallback(CallbackMethod),
                "The call executed on thread {0}, with return value \"{1}\".");

caller2.BeginInvoke(2, 3, CallbackMethod2, "this is add");
            Console.WriteLine("The main thread {0} continues to execute...",
                Thread.CurrentThread.ManagedThreadId);
            Thread.Sleep(4000);

            Console.WriteLine("The main thread ends.");
        }

        // The callback method must have the same signature as the
        // AsyncCallback delegate.
        private void CallbackMethod(IAsyncResult ar)
        {
            // Retrieve the delegate.
            AsyncResult result = (AsyncResult) ar;
   //强制转换成对应的委托对象
            AsyncMethodCaller caller = (AsyncMethodCaller) result.AsyncDelegate;

            // Retrieve the format string that was passed as state
            // information.
            string formatString = (string) ar.AsyncState;

            // Define a variable to receive the value of the out parameter.
            // If the parameter were ref rather than out then it would have to
            // be a class-level field so it could also be passed to BeginInvoke.
            int threadId = 0;
            // Call EndInvoke to retrieve the results.
            string returnValue = caller.EndInvoke(out threadId, ar);

            // Use the format string to format the output message.
            Console.WriteLine(formatString, threadId, returnValue);
        }
private void CallbackMethod2(IAsyncResult ar)
        {
            // Retrieve the delegate.
            AsyncResult result = (AsyncResult)ar;
//强制转换成对应的委托对象
            AsyncMethodCaller2 caller = (AsyncMethodCaller2)result.AsyncDelegate;

            // 取得状态
            string formatString = (string)ar.AsyncState;
            //调用异步完成的方法，取得执行结果
            string returnValue = caller.EndInvoke(ar).ToString();

//此种方式是在windows应用程序给控件赋值时用，因为在非创建线程不能操作控件
            this.Invoke(new Action<string>((u) => tb_datainfo.Text += u), returnValue);
            //tb_datainfo.Text = caller.EndInvoke(out threadId, ar);

            // Use the format string to format the output message.
            //Console.WriteLine(formatString, threadId, returnValue);
        }
    }
    }
}