C# 异步编程小结

1. APM 异步编程模型，Asynchronous Programming Model
2. EAP 基于事件的异步编程模式，Event-based Asynchronous Pattern
3. TAP 基于任务的异步编程模式，Task-based Asynchronous Pattern

APM(早期的异步编程模型)

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该编程模型使用BeginXXX,EndXXX方法和IAsyncResult接口

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace AsyncProgramTest
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public class RequestState
        {
            // This class stores the State of the request.
            const int BUFFER_SIZE = 1024;
            public StringBuilder requestData;
            public byte[] BufferRead;
            public HttpWebRequest request;
            public HttpWebResponse response;
            public Stream streamResponse;
            public RequestState()
            {
                BufferRead = new byte[BUFFER_SIZE];
                requestData = new StringBuilder("");
                request = null;
                streamResponse = null;
            }
        }
        public MainWindow()
        {
            InitializeComponent();


        }
        const int BUFFER_SIZE = 1024;
        private void button_Click(object sender, RoutedEventArgs e)
        {
            HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create("http://www.cnblogs.com/");

            RequestState myRequestState = new RequestState();
            myRequestState.request = myHttpWebRequest;
            IAsyncResult result =(IAsyncResult)myHttpWebRequest.BeginGetResponse(new AsyncCallback(RespCallback), myRequestState);

        }
        private void RespCallback(IAsyncResult asynchronousResult)
        {
            RequestState myRequestState = (RequestState)asynchronousResult.AsyncState;
            HttpWebRequest myHttpWebRequest = myRequestState.request;
            myRequestState.response = (HttpWebResponse)myHttpWebRequest.EndGetResponse(asynchronousResult);

            // Read the response into a Stream object.
            Stream responseStream = myRequestState.response.GetResponseStream();
            myRequestState.streamResponse = responseStream;

            // Begin the Reading of the contents of the HTML page and print it to the console.
            IAsyncResult asynchronousInputRead = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
            return;

        }
        private static void ReadCallBack(IAsyncResult asyncResult)
        {
            RequestState myRequestState = (RequestState)asyncResult.AsyncState;
            Stream responseStream = myRequestState.streamResponse;
            int read = responseStream.EndRead(asyncResult);
            // Read the HTML page and then print it to the console.
            if (read > 0)
            {
                myRequestState.requestData.Append(Encoding.UTF8.GetString(myRequestState.BufferRead, 0, read));
                IAsyncResult asynchronousResult = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
                return;
            }
            else
            {
                Console.WriteLine("
The contents of the Html page are : ");
                if (myRequestState.requestData.Length > 1)
                {
                    string stringContent;
                    stringContent = myRequestState.requestData.ToString();
                    Console.WriteLine(stringContent);
                }
                Console.WriteLine("Press any key to continue..........");
                Console.ReadLine();

                responseStream.Close();
            }
        }
    }
}

EAP(基于事件的异步编程模式)

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TAP(基于任务的异步编程模式)

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  private async void button_Click(object sender, RoutedEventArgs e)
        {
            System.Net.Http.HttpClient httpClient = new System.Net.Http.HttpClient();
            var msg = await httpClient.GetAsync("http://www.cnblogs.com/");
            var htmlString=await msg.Content.ReadAsStringAsync();
            //todo process htmlstring 
        }

 EAP=>TAP(基于事件的异步编程模式转化为基于任务的异步编程模式)

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APM=>TAP(BeginXXX转化为基于任务的异步编程模型)

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     private async  void button_Click(object sender, RoutedEventArgs e)
        {
            HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create("http://www.cnblogs.com/");

            var maskTask = Task.Factory.FromAsync<WebResponse>(myHttpWebRequest.BeginGetResponse,myHttpWebRequest.EndGetResponse,  null, TaskCreationOptions.None);
            WebResponse webResponse = await maskTask;
            Stream responseStream = webResponse.GetResponseStream();

            using (StreamReader reader = new StreamReader(responseStream))
            {
                var htmlString =await reader.ReadToEndAsync();
           
                Console.WriteLine(htmlString);
            //to do process html String 

            }
        }

 参考文章：http://www.dotblogs.com.tw/yc421206/archive/2013/08/06/113555.aspx