后台代码:

public partial class MainPage : PhoneApplicationPage    {        private long siz;        private long speed;        private Stopwatch sw;        private Stopwatch sw1;        public MainPage()        {            InitializeComponent();        }        private void button1_Click(object sender, RoutedEventArgs e)        {            testspeed();        }        public void testspeed()        {            WebClient client = new WebClient();            progressBar1.Value = 0.0;            textBox2.Text = "0 %";            client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(this.webClient_DownloadStringCompleted);            client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(this.webClient_DownloadProgressChanged);            sw = Stopwatch.StartNew();//用来记录总的下载时间            sw1 = Stopwatch.StartNew();//用来记录下载过程中的时间片，用于计算临时速度            client.DownloadStringAsync(new Uri("http://dl_dir.qq.com/qqfile/qq/QQ2011/QQ2011.exe"));        }        //下载过程事件        public void webClient_DownloadProgressChanged(object s, DownloadProgressChangedEventArgs e)        {            textBox2.Text = e.ProgressPercentage.ToString() + " %";            sw1.Stop();            long num = e.BytesReceived / 1024;            if (sw1.Elapsed.Seconds != 0)            {                speed = num / ((long)sw1.Elapsed.Seconds);            }            textBlock4.Text = this.speed + " KB/s";            progressBar1.Value = e.ProgressPercentage;            siz = e.TotalBytesToReceive;            textBlock3.Text = siz/1024/1024 + "MB";            sw1.Start();        }        //下载完成事件        public void webClient_DownloadStringCompleted(object s, DownloadStringCompletedEventArgs e)        {            sw.Stop();            siz = siz / 1024;            long num = siz / ((long)sw.Elapsed.Seconds);            sw.Reset();            textBox1.Text = "下载完成！";            textBlock1.Text = num + " KB/s";        }    }}

XAML 设计代码:

运行结果图: