using System.IO;
using System.Windows.Media.Imaging;
using System.Text;
namespace fileup
{
    public partial class MainPage : UserControl
    {
        OpenFileDialog openfile = new OpenFileDialog();
        public MainPage()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            //openfile.Filter = "Jpeg Files (*.jpg)|*.jpg";//限制文件类型为图片
            openfile.Multiselect = false;//不允许多选 
            if (openfile.ShowDialog() == true)
            {
                if (openfile.File != null)
                {
                    //BitmapImage bmp = new BitmapImage();
                    //bmp.SetSource(openfile.File.OpenRead());
                    //image1.Source = bmp;
                    WebClient webclient = new WebClient();
                    Uri uri = new Uri("http://localhost:51594/upload.ashx?name=" + openfile.File.Name, UriKind.RelativeOrAbsolute);
                    webclient.OpenWriteAsync(uri, "POST", openfile.File.OpenRead());
                    webclient.Headers["Content-Type"] = "multipart/form-data";
                    webclient.OpenWriteCompleted += new OpenWriteCompletedEventHandler(webclient_OpenWriteCompleted);
                }
                else
                {
                    MessageBox.Show("请选择图片！");
                }
            }
        }

        void webclient_OpenWriteCompleted(object sender, OpenWriteCompletedEventArgs e)
        {
            Stream stream = e.UserState as Stream;
            Stream serverStream = e.Result;
            byte[] buffer = new byte[4096];
            int readcount = 0;
            //  将需要上传的流读取到指定的字节数组中
            while ((readcount = stream.Read(buffer, 0, buffer.Length)) > 0)
            {
                // 将指定的字节数组写入到目标地址的流
                serverStream.Write(buffer, 0, readcount);
            }
            serverStream.Close();
            stream.Close();
            MessageBox.Show("上传成功！");
        }
    }
}上面两句标记为红色的部分不是太理解，为什么要把上传的数据流读取到e.result()转化的流中，还有把数据传到Hander.ashx处理程序的原理?