Silverlight上传下载三种方式解析（二）

WebClient思路及功能实现

实现思路：通过新建一个“一般处理程序”WebClientUpLoadStreamHandler.ashx配合完成,
Silverlight打开文件，获取文件流，webclient调用openwrite方法，请求服务器，打开一个可以写进流InputStream。
当该可写进流可用的时候，相应openwrite异步方法的一个回调事件，在该事件中将文件流写进到HTTP的可写进流。服务器端接收到输进流后写进到文件流保存。
服务端使用ASHX一般处理程序来作为接受页。
本程序中添加“一般处理程序”及其用法介绍请单击此处，关于一般处理程序的详细理论介绍请参考http://www.cnblogs.com/JimmyZhang/archive/2007/09/15/894124.html
上传功能实现 一．选择本地图片并指定上传处理上传的一般处理程序
/// <summary>
/// 上传事件通过对话框来选择上传文件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void buttonUpload_Click(object sender, RoutedEventArgs e)
{
            OpenFileDialog openFileDialog = new OpenFileDialog();
            openFileDialog.Filter = "Jpeg Files (*.jpg)|*.jpg|All Files(*.*)|*.*";
            openFileDialog.Multiselect = false;
            if (openFileDialog.ShowDialog()==true)
            {
                   fileinfo = openFileDialog.File;
                   if (fileinfo!=null)
                   {
                            WebClient webclient = new WebClient();
                            string uploadFileName = fileinfo.Name.ToString();
                            Uri upTargetUri = new Uri(String.Format                     ("http://localhost:"+HtmlPage.Document.DocumentUri.Port+"/WebClientUpLoadStreamHandler.ashx?fileName={0}", uploadFileName), UriKind.Absolute); //指定上传处理程序
                            webclient.OpenWriteCompleted += new OpenWriteCompletedEventHandler (webclient_OpenWriteCompleted);
                             //webclient.Headers["Content-Type"] = "multipart/from-data";
                             webclient.OpenWriteAsync(upTargetUri, "POST", fileinfo.OpenRead());
                             webclient.WriteStreamClosed += new WriteStreamClosedEventHandler(webclient_WriteStreamClosed);
                     }
                      else
                      {
                                    MessageBox.Show("请选择想要上传的图片！！！");
          }
      }
}
void webclient_OpenWriteCompleted(object sender, OpenWriteCompletedEventArgs e)
{
                //将图片数据流发送到服务器上 e.UserState即为需要上传的客户端的流
                Stream clientStream = 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 = clientStream.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();
              clientStream.Close();
}
void webclient_WriteStreamClosed(object sender, WriteStreamClosedEventArgs e)
{
      if (e.Error!=null)
     {
              System.Windows.Browser.HtmlPage.Window.Alert(e.Error.Message);
      }
      else
     {
                 System.Windows.Browser.HtmlPage.Window.Alert("图片上传成功！！！");
                 c.GetFileListAsync();//这里是使用了WCF服务返回一下服务端的文件列表，共下载时选择
       }
}
二．服务端获得上传流，并保存文件
服务端使用了一般处理程序来配合完成，如何添加一般处理程序请点击此处
public void ProcessRequest(HttpContext context)
{
            string fileNamestr = context.Request.QueryString["fileName"];
            Stream sr = context.Request.InputStream;//从客户端获得传入到服务端的文件流
            try
            {
                  byte[] buffer = new byte[4096];
                  int bytestRead = 0;
                  //将当前数据流写入服务器端指定文件夹下
                 string targetPath = context.Server.MapPath("UploadFiles/"+fileNamestr);
                 using (FileStream fs = File.Create(targetPath, 4096))
                {/
                       //将当前流读入到字节数组中
                      while ((bytestRead = sr.Read(buffer, 0, buffer.Length)) > 0)
                      {
                               fs.Write(buffer, 0, bytestRead);
                      }
                }
                context.Response.ContentType = "text/plain";
                context.Response.Write("上传成功");
          }
          catch (Exception e)
          {
                 context.Response.ContentType = "text/plain";
                 context.Response.Write("上传失败，错误信息：" + e.Message);
           }
           finally { sr.Dispose(); }
}
下载功能实现 在客户端直接调用WebClient的自带方法和事件即可完成下载功能
private void buttonDownload_Click(object sender, RoutedEventArgs e)
{
            if (listBox1.SelectedItems.Count<0)
            {
                      MessageBox.Show("请选择要下载的下载文件");
            }
            else if (listBox1.SelectedItems.Count>1)
            {
                        MessageBox.Show("暂不提供批量下载");
              }
              else
              {
                       string imgUrl = "http://localhost:" + HtmlPage.Document.DocumentUri.Port + "/UploadFiles/" + listBox1.SelectedItem.ToString();
                        Uri endpoint = new Uri(imgUrl);
                       WebClient client = new WebClient();
                       //调用WebClient自身事件
                        client.OpenReadCompleted += new OpenReadCompletedEventHandler(client_OpenReadCompleted);
                        client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(client_DownloadProgressChanged);
                       //调用自身的Read方法完成下载
                      client.OpenReadAsync(endpoint);
                }
}