Windows Phone开发 使用HttpWebRequest异步下载

在Windows Phone中,HttpWebRequest和WebClient都是异步的,但网上很多文章说WebClient因为回调在UI线程,对性能会有点影响,目前我自己的app就是用WebClient实现,确实会影响UI线程,进度条也会卡。下面是一个使用HttpWebRequest异步下载的完整例子:


using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using System.IO;

namespace WebRequest
{
    public partial class MainPage : PhoneApplicationPage
    {
        // Constructor
        delegate void DownDelegate(string content);
        DownDelegate downDelegate;
        //委托
        public MainPage()
        {
            InitializeComponent();
           
        }
        private void setConent(string content)
        {
            textBlock1.Text = content;
        }
        private void ResponseCallback(IAsyncResult result)
        {
            HttpWebRequest request = (HttpWebRequest)result.AsyncState;
            WebResponse response = request.EndGetResponse(result);
            using (Stream stream = response.GetResponseStream())
            {
                using (StreamReader reader = new StreamReader(stream))
                {
                    string contents = reader.ReadToEnd();
                    Dispatcher.BeginInvoke(downDelegate, contents);//特别注意需要通过Dispatcher去更新UI进程
                }
            }
        }
        private void button1_Click(object sender, RoutedEventArgs e)
        {
            string url = "http://www.pocketdigi.com";
            downDelegate = setConent;
            System.Net.WebRequest request = HttpWebRequest.Create(url);
            IAsyncResult result = (IAsyncResult)request.BeginGetResponse(ResponseCallback, request);
            //完成后调用委托,更新UI
        }

    }
}

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