.Net异步机制

引自博客：Yes I Can 什么是.Net异步调用机制

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.ComponentModel;//ISynchronizeInvoke
using System.Runtime.Remoting.Messaging;//AsyncResult
using System.Windows.Forms;
using System.Threading;

namespace WinApp
{
    public class AsyncQueryHelper
    {
        FrmProgressBar frmProgressBar = null;

        public AsyncQueryHelper()
        {
            frmProgressBar = new FrmProgressBar(10);
        }

        public delegate DataSet ExecQueryHandler(DataSet dsRequest);
        public ExecQueryHandler execQueryHandlerInstance = null;

        private AsyncCallback asyncCallbackInstance = null;
        public void ExecQuery(DataSet dsRequest)
        {
            frmProgressBar.StartThread();
            asyncCallbackInstance = new AsyncCallback(ExecAsyncCallBack);//<=>asyncCallbackInstance = ExecAsyncCallBack;

            if (execQueryHandlerInstance != null)
            {
                //execQueryHandlerInstance.BeginInvoke(dsRequest, asyncCallbackInstance, execQueryHandlerInstance);
                IAsyncResult result = execQueryHandlerInstance.BeginInvoke(dsRequest, ExecAsyncCallBack, execQueryHandlerInstance);//同上

                //=======================WaitOne=======================//
                //阻碍当前线程，直到异步调用结束
                result.AsyncWaitHandle.WaitOne();
                //开始其他工作.
                //DoAnotherWork();

                //=======================WaitAll=======================//
                /*
                IAsyncResult result1 = execQueryHandlerInstance.BeginInvoke(dsRequest, ExecAsyncCallBack, execQueryHandlerInstance);
                IAsyncResult result2 = execQueryHandlerInstance.BeginInvoke(dsRequest, ExecAsyncCallBack, execQueryHandlerInstance);
                //把所有异步的句柄保存到WaitHandle 对象中
                WaitHandle[] waitHandles = { result1.AsyncWaitHandle, result2.AsyncWaitHandle };
                //阻碍当前线程,直到所有异步调用结束
                WaitHandle.WaitAll(waitHandles);
                //开始其他工作
                //DoAnotherWork();
                */

                //====WaitAny:可以使用 WaitAny 来指定某个/某几个委托先等待=====//
                /*
                 WaitHandle[] oneWaitHandle = { result1.AsyncWaitHandle };
                 WaitHandle.WaitAny(oneWaitHandle);
                 //开始其他工作
                 //DoAnotherWork();
                */
            }
        }

        public delegate void BindDataToGrid(DataSet dsReponse);
        public BindDataToGrid bindDataToGridInstance = null;

        public DataGridView dataGridView = null;
        public void ExecAsyncCallBack(IAsyncResult asyncResult)
        {
            endHandlerInstance = new EndHandler(frmProgressBar.EndThread);
            frmProgressBar.BeginInvoke(endHandlerInstance, null);//执行控件的BeginInvoke

            ////======================1=========================////
            //此处的asyncResult.AsyncState对象就是BeginInvoke里的最后一个参数
            /*
            ExecQueryHandler execQueryHandler = asyncResult.AsyncState as ExecQueryHandler;
            DataSet dsReponse = null;
            if (asyncResult.IsCompleted)
            {
                if (execQueryHandler != null)
                {
                    dsReponse = new DataSet();
                    dsReponse = execQueryHandler.EndInvoke(asyncResult);
                    ISynchronizeInvoke async = this.dataGridView;
                    if (async.InvokeRequired)
                    {
                        async.Invoke(bindDataToGridInstance, new object[] { dsReponse });
                    }
                }
            }
            */

            ////======================2=========================////
            AsyncResult originAsyncResult = asyncResult as AsyncResult;
            if (originAsyncResult != null)
            {
                ExecQueryHandler execQuery = (ExecQueryHandler)originAsyncResult.AsyncDelegate;
                DataSet dsReponse = execQuery.EndInvoke(asyncResult);

                ISynchronizeInvoke async = this.dataGridView;
                //InvokeRequired == false表示来自主线程；为true表示来自异步线程
                if (dataGridView != null && bindDataToGridInstance != null)
                {
                    if (async.InvokeRequired)
                    {
                        async.Invoke(bindDataToGridInstance, new object[] { dsReponse });
                    }
                }
                asyncResult.AsyncWaitHandle.Close();//显示的释放资源
            }
        }

        public delegate void SendRequestHandler();
        public SendRequestHandler sendRequestHandlerInstance = null;

        public delegate void EndHandler();
        public EndHandler endHandlerInstance = null;


        static void DoAnotherJob()
        {
            Thread.Sleep(1000);//需要1秒才能完成这个工作
            MessageBox.Show("[{0}]:Do Another Job", DateTime.Now.ToString());
        }

    }
}

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace WinApp
{
    public class AsyncReadWrite
    {
        //同步读文件
        public static string SyncRead()
        {
            string path = @"d:\test.txt";
            FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, 20480, false);
            StringBuilder sbReadResult = new StringBuilder();
            using (fs)
            {
                byte[] data = new byte[1024];
                int nbyteReads;
                do
                {
                    nbyteReads = fs.Read(data, 0, data.Length);
                    sbReadResult.Append(Encoding.Default.GetString(data, 0, nbyteReads));
                } while (nbyteReads > 0);
                //Console.WriteLine(sbReadResult.ToString());
            }
            //Console.ReadLine();
            return sbReadResult.ToString().Trim();
        }

        //异步读文件
        public static string AsyncRead()
        {
            string path = @"d:\Query.txt";
            byte[] data = new byte[1024];
            FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, 20480, true);
            StringBuilder sbReadResult = new StringBuilder();
            AsyncCallback asyncCallback = null;
            //匿名方法
            asyncCallback = delegate(IAsyncResult asyncResult)
            {
                int nRead = fs.EndRead(asyncResult);
                sbReadResult.Append(Encoding.Default.GetString(data, 0, nRead));

                if (nRead > 0)
                {
                    fs.BeginRead(data, 0, 1024, asyncCallback, null);
                }
                else
                {
                    fs.Close();//显示释放托管堆资源
                }
            };
            IAsyncResult asyncReadResult = fs.BeginRead(data, 0, 1024, asyncCallback, null);
            return sbReadResult.ToString().Trim();
        }

        //异步写文件
        public static void AsyncWrite(string content)
        {
            string path = @"d:\write.txt";
            FileStream fs = new FileStream(path, FileMode.Create, FileAccess.ReadWrite, FileShare.None, 20480, true);
            byte[] data = Encoding.Default.GetBytes(content);
            AsyncCallback asyncCallback = null;
            asyncCallback = delegate(IAsyncResult async)
            {
                fs.EndWrite(async);
                fs.Close();//显示释放托管堆资源
            };
            IAsyncResult asyncWriteResult = fs.BeginWrite(data, 0, data.Length, asyncCallback, null);
            Console.ReadLine();
        }
    }
}