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);

}

}