下载数据

作者：webabcd

介绍
Silverlight 2.0 详解WebClient，以字符串的形式上传、下载数据；以流的方式上传、下载数据
    WebClient - 将数据发送到指定的 URI，或者从指定的 URI 接收数据的类
        DownloadStringAsync(Uri address, Object userToken) - 以字符串的形式下载指定的 URI 的资源
        UploadStringAsync(Uri address, string data) - 以字符串的形式上传数据到指定的 URI。所使用的 HTTP 方法默认为 POST
        OpenReadAsync(Uri address, Object userToken) - 以流的形式下载指定的 URI 的资源
        OpenWriteAsync(Uri address, string method, Object userToken) - 打开流以使用指定的方法向指定的 URI 写入数据

在线DEMO
http://www.cnblogs.com/webabcd/archive/2008/10/09/1307486.html

示例
1、以字符串的形式和流的形式下载数据
WebClientDownload.xaml

<UserControl x:Class="Silverlight20.Communication.WebClientDownload"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

</StackPanel>

</StackPanel>

</UserControl>

WebClientDownload.xaml.cs

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 System.IO;

namespace Silverlight20.Communication

{

public partial class WebClientDownload : UserControl

{

// 用于演示以字符串的形式下载数据

string _urlString = "http://localhost/Files/Demo.zip";

// 用于演示以流的形式下载数据

string _urlStream = "http://localhost/Files/Logo.png";

public WebClientDownload()

{

InitializeComponent();

// 演示字符串式下载

DownloadStringDemo();

// 演示流式下载

DownloadStreamDemo();

}

/// <summary>

/// 演示字符串式下载

/// </summary>

void DownloadStringDemo()

{

Uri uri = new Uri(_urlString, UriKind.Absolute);

* WebClient - 将数据发送到指定的 URI，或者从指定的 URI 接收数据的类

* DownloadStringCompleted - 下载数据完毕后（包括取消操作及有错误发生时）所触发的事件

* DownloadProgressChanged - 下载数据过程中所触发的事件。正在下载或下载完全部数据后会触发

* DownloadStringAsync(Uri address, Object userToken) - 以字符串的形式下载指定的 URI 的资源

* Uri address - 需要下载的资源地址

* Object userToken - 用户标识

System.Net.WebClient clientDownloadString = new System.Net.WebClient();

clientDownloadString.DownloadStringCompleted += new DownloadStringCompletedEventHandler(clientDownloadString_DownloadStringCompleted);

clientDownloadString.DownloadProgressChanged += new DownloadProgressChangedEventHandler(clientDownloadString_DownloadProgressChanged);

clientDownloadString.DownloadStringAsync(uri, "userToken");

}

void clientDownloadString_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)

{

* DownloadProgressChangedEventArgs.ProgressPercentage - 下载完成的百分比

* DownloadProgressChangedEventArgs.BytesReceived - 当前收到的字节数

* DownloadProgressChangedEventArgs.TotalBytesToReceive - 总共需要下载的字节数

* DownloadProgressChangedEventArgs.UserState - 用户标识

lblMsgString.Text = string.Format("下载完成的百分比：{0}\r\n当前收到的字节数：{1}\r\n总共需要下载的字节数：{2}\r\n",

e.ProgressPercentage.ToString() + "%",

e.BytesReceived.ToString(),

e.TotalBytesToReceive.ToString());

progressBarString.Value = (double)e.ProgressPercentage;

}

void clientDownloadString_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)

{

* DownloadStringCompletedEventArgs.Error - 该异步操作期间是否发生了错误

* DownloadStringCompletedEventArgs.Cancelled - 该异步操作是否已被取消

* DownloadStringCompletedEventArgs.Result - 下载后的字符串类型的数据

* DownloadStringCompletedEventArgs.UserState - 用户标识

if (e.Error != null)

{

lblMsgString.Text += e.Error.ToString();

return;

}

if (e.Cancelled != true)

{

lblMsgString.Text += string.Format("用户标识：{0}", e.UserState.ToString());

}

/// <summary>

/// 演示流式下载

/// </summary>

void DownloadStreamDemo()

{

Uri uri = new Uri(_urlStream, UriKind.Absolute);

* WebClient - 将数据发送到指定的 URI，或者从指定的 URI 接收数据的类

* IsBusy - 指定的web请求是否正在进行中

* CancelAsync() - 取消指定的异步操作

* OpenReadCompleted - 数据读取完毕后（包括取消操作及有错误发生时）所触发的事件。流的方式

* DownloadProgressChanged - 下载数据过程中所触发的事件。正在下载或下载完全部数据后会触发

* OpenReadAsync(Uri address, Object userToken) - 以流的形式下载指定的 URI 的资源

* Uri address - 需要下载的资源地址

* Object userToken - 用户标识

System.Net.WebClient clientDownloadStream = new System.Net.WebClient();

if (clientDownloadStream.IsBusy)

clientDownloadStream.CancelAsync();

clientDownloadStream.OpenReadCompleted += new OpenReadCompletedEventHandler(clientDownloadStream_OpenReadCompleted);

clientDownloadStream.DownloadProgressChanged += new DownloadProgressChangedEventHandler(clientDownloadStream_DownloadProgressChanged);

clientDownloadStream.OpenReadAsync(uri);

}

void clientDownloadStream_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)

{

* DownloadProgressChangedEventArgs.ProgressPercentage - 下载完成的百分比

* DownloadProgressChangedEventArgs.BytesReceived - 当前收到的字节数

* DownloadProgressChangedEventArgs.TotalBytesToReceive - 总共需要下载的字节数

* DownloadProgressChangedEventArgs.UserState - 用户标识

lblMsgString.Text = string.Format("下载完成的百分比：{0}\r\n当前收到的字节数：{1}\r\n总共需要下载的字节数：{2}\r\n",

e.ProgressPercentage.ToString() + "%",

e.BytesReceived.ToString(),

e.TotalBytesToReceive.ToString());

progressBarStream.Value = (double)e.ProgressPercentage;

}

void clientDownloadStream_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)

{

* OpenReadCompletedEventArgs.Error - 该异步操作期间是否发生了错误

* OpenReadCompletedEventArgs.Cancelled - 该异步操作是否已被取消

* OpenReadCompletedEventArgs.Result - 下载后的 Stream 类型的数据

* OpenReadCompletedEventArgs.UserState - 用户标识

if (e.Error != null)

{

lblMsgStream.Text += e.Error.ToString();

return;

}

if (e.Cancelled != true)

{

System.Windows.Media.Imaging.BitmapImage imageSource = new System.Windows.Media.Imaging.BitmapImage();

imageSource.SetSource(e.Result);

img.Source = imageSource;

}

2、以字符串的形式和流的形式上传数据
REST.cs（WCF创建的用于演示以字符串的形式和流的形式上传数据的REST服务）

using System;

using System.Linq;

using System.Runtime.Serialization;

using System.ServiceModel;

using System.ServiceModel.Activation;

using System.ServiceModel.Web;

using System.Collections.Generic;

using System.Text;

using System.IO;

/// <summary>

/// 提供 REST 服务的类

/// 注：Silverlight只支持 GET 和 POST

/// </summary>

[ServiceContract]

[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]

public class REST

{

/// <summary>

/// 用于演示返回 JSON（对象）的 REST 服务

/// </summary>

/// <param name="name"></param>

/// <returns></returns>

[OperationContract]

[WebGet(UriTemplate = "User/{name}/json", ResponseFormat = WebMessageFormat.Json)]

public User HelloJson(string name)

{

return new User { Name = name, DayOfBirth = new DateTime(1980, 2, 14) };

}

/// <summary>

/// 用于演示返回 JSON（集合）的 REST 服务

/// </summary>

/// <returns></returns>

[OperationContract]

[WebGet(UriTemplate = "Users/json", ResponseFormat = WebMessageFormat.Json)]

public List<User> HelloJson2()

{

return new List<User>

{

new User(){ Name = "webabcd01", DayOfBirth = new DateTime(1980, 1, 1) },

new User(){ Name = "webabcd02", DayOfBirth = new DateTime(1980, 2, 2) },

new User(){ Name = "webabcd03", DayOfBirth = new DateTime(1980, 3, 3) },

};

}

/// <summary>

/// 用于演示返回 XML（对象）的 REST 服务

/// </summary>

/// <param name="name"></param>

/// <returns></returns>

[OperationContract]

[WebGet(UriTemplate = "User/{name}/xml", ResponseFormat = WebMessageFormat.Xml)]

public User HelloXml(string name)

{

return new User { Name = name, DayOfBirth = new DateTime(1980, 2, 14) };

}

/// <summary>

/// 用于演示返回 XML（集合）的 REST 服务

/// </summary>

/// <returns></returns>

[OperationContract]

[WebGet(UriTemplate = "Users/xml", ResponseFormat = WebMessageFormat.Xml)]

public List<User> HelloXml2()

{

return new List<User>

{

new User(){ Name = "webabcd01", DayOfBirth = new DateTime(1980, 1, 1) },

new User(){ Name = "webabcd02", DayOfBirth = new DateTime(1980, 2, 2) },

new User(){ Name = "webabcd03", DayOfBirth = new DateTime(1980, 3, 3) },

};

}

/// <summary>

/// 用于演示以字符串的形式上传数据的 REST 服务

/// </summary>

/// <param name="fileName">上传的文件名</param>

/// <param name="stream">POST 过来的数据</param>

/// <returns></returns>

[OperationContract]

[WebInvoke(UriTemplate = "UploadString/?fileName={fileName}", Method = "POST", ResponseFormat = WebMessageFormat.Json)]

public bool UploadString(string fileName, Stream stream)

{

// 文件的服务端保存路径

string path = Path.Combine("C:\\", fileName);

try

{

using (StreamReader sr = new StreamReader(stream))

{

// 将 POST 过来的被 Base64 编码过字符串传换成 byte[]

byte[] buffer = Convert.FromBase64String(sr.ReadToEnd());

using (FileStream fs = new FileStream(path, FileMode.Create, FileAccess.Write, FileShare.None))

{

// 将文件写入到服务端

fs.Write(buffer, 0, buffer.Length);

}

return true;

}

catch

{

return false;

}

/// <summary>

/// 用于演示以流的形式上传数据的 REST 服务

/// </summary>

/// <param name="fileName">上传的文件名</param>

/// <param name="stream">POST 过来的数据（流的方式）</param>

/// <returns></returns>

[OperationContract]

[WebInvoke(UriTemplate = "UploadStream/?fileName={fileName}", Method = "POST", ResponseFormat = WebMessageFormat.Json)]

public bool UploadStream(string fileName, Stream stream)

{

// 文件的服务端保存路径

string path = Path.Combine("C:\\", fileName);

try

{

using (FileStream fs = new FileStream(path, FileMode.Create, FileAccess.Write, FileShare.None))

{

byte[] buffer = new byte[4096];

int count = 0;

// 每 POST 过来 4096 字节的数据，往服务端写一次

while ((count = stream.Read(buffer, 0, buffer.Length)) > 0)

{

fs.Write(buffer, 0, count);

}

return true;

}

catch

{

return false;

}

WebClientUpload.xaml

<UserControl x:Class="Silverlight20.Communication.WebClientUpload"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

</StackPanel>

</StackPanel>

</UserControl>

WebClientUpload.xaml.cs

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 System.IO;

using System.Windows.Resources;

using System.ComponentModel;

using System.Windows.Browser;

namespace Silverlight20.Communication

{

public partial class WebClientUpload : UserControl

{

// 用于演示以字符串的形式上传数据

string _urlString = "http://localhost:3036/REST.svc/UploadString/?fileName=";

// 用于演示以流的形式上传数据

string _urlStream = "http://localhost:3036/REST.svc/UploadStream/?fileName=";

public WebClientUpload()

{

InitializeComponent();

}

/// <summary>

/// 演示字符串式上传

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

private void btnString_Click(object sender, RoutedEventArgs e)

{

string data = "";

* OpenFileDialog - 文件对话框

* ShowDialog() - 显示文件对话框。在文件对话框中单击“确定”则返回true，反之则返回false

* File - 所选文件的 FileInfo 对象

OpenFileDialog dialog = new OpenFileDialog();

if (dialog.ShowDialog() == true)

{

using (FileStream fs = dialog.File.OpenRead())

{

byte[] buffer = new byte[fs.Length];

fs.Read(buffer, 0, buffer.Length);

// 将指定的 byte[] 转换为字符串（使用Base64编码）

data = Convert.ToBase64String(buffer);

}

* WebClient - 将数据发送到指定的 URI，或者从指定的 URI 接收数据的类

* UploadStringCompleted - 上传数据完毕后（包括取消操作及有错误发生时）所触发的事件

* UploadProgressChanged - 上传数据过程中所触发的事件。正在上传或上传完全部数据后会触发

* Headers - 与请求相关的的标头的 key/value 对集合

* UploadStringAsync(Uri address, string data) - 以字符串的形式上传数据到指定的 URI。所使用的 HTTP 方法默认为 POST

* Uri address - 接收上传数据的 URI

* string data - 需要上传的数据

System.Net.WebClient clientUploadString = new System.Net.WebClient();

clientUploadString.UploadStringCompleted += new UploadStringCompletedEventHandler(clientUploadString_UploadStringCompleted);

clientUploadString.UploadProgressChanged += new UploadProgressChangedEventHandler(clientUploadString_UploadProgressChanged);

Uri uri = new Uri(_urlString + dialog.File.Name, UriKind.Absolute);

clientUploadString.Headers["Content-Type"] = "application/x-www-form-urlencoded";

clientUploadString.UploadStringAsync(uri, data);

}

void clientUploadString_UploadProgressChanged(object sender, UploadProgressChangedEventArgs e)

{

* UploadProgressChangedEventArgs.ProgressPercentage - 上传完成的百分比

* UploadProgressChangedEventArgs.BytesSent - 当前发送的字节数

* UploadProgressChangedEventArgs.TotalBytesToSend - 总共需要发送的字节数

* UploadProgressChangedEventArgs.BytesReceived - 当前接收的字节数

* UploadProgressChangedEventArgs.TotalBytesToReceive - 总共需要接收的字节数

* UploadProgressChangedEventArgs.UserState - 用户标识

lblMsgString.Text = string.Format("上传完成的百分比：{0}\r\n当前发送的字节数：{1}\r\n总共需要发送的字节数：{2}\r\n当前接收的字节数：{3}\r\n总共需要接收的字节数：{4}\r\n",

e.ProgressPercentage.ToString(),

e.BytesSent.ToString(),

e.TotalBytesToSend.ToString(),

e.BytesReceived.ToString(),

e.TotalBytesToReceive.ToString());

progressBarString.Value = (double)e.ProgressPercentage;

}

void clientUploadString_UploadStringCompleted(object sender, UploadStringCompletedEventArgs e)

{

* UploadStringCompletedEventArgs.Error - 该异步操作期间是否发生了错误

* UploadStringCompletedEventArgs.Cancelled - 该异步操作是否已被取消

* UploadStringCompletedEventArgs.Result - 服务端返回的数据（字符串类型）

* UploadStringCompletedEventArgs.UserState - 用户标识

if (e.Error != null)

{

lblMsgString.Text += e.Error.ToString();

return;

}

if (e.Cancelled != true)

{

var jsonObject = System.Json.JsonObject.Parse(e.Result);

lblMsgString.Text += string.Format("是否上传成功：{0}",

(bool)jsonObject);

}

/// <summary>

/// 演示流式上传

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

private void btnStream_Click(object sender, RoutedEventArgs e)

{

FileStream fs = null;

OpenFileDialog dialog = new OpenFileDialog();

if (dialog.ShowDialog() == true)

{

fs = dialog.File.OpenRead();

* WebClient - 将数据发送到指定的 URI，或者从指定的 URI 接收数据的类

* OpenWriteCompleted - 在打开用于上传的流完成时（包括取消操作及有错误发生时）所触发的事件

* WriteStreamClosed - 在写入数据流的异步操作完成时（包括取消操作及有错误发生时）所触发的事件

* UploadProgressChanged - 上传数据过程中所触发的事件。如果调用 OpenWriteAsync() 则不会触发此事件

* Headers - 与请求相关的的标头的 key/value 对集合

* OpenWriteAsync(Uri address, string method, Object userToken) - 打开流以使用指定的方法向指定的 URI 写入数据

* Uri address - 接收上传数据的 URI

* string method - 所使用的 HTTP 方法（POST 或 GET）

* Object userToken - 需要上传的数据流

System.Net.WebClient clientUploadStream = new System.Net.WebClient();

clientUploadStream.OpenWriteCompleted += new OpenWriteCompletedEventHandler(clientUploadStream_OpenWriteCompleted);

clientUploadStream.UploadProgressChanged += new UploadProgressChangedEventHandler(clientUploadStream_UploadProgressChanged);

clientUploadStream.WriteStreamClosed += new WriteStreamClosedEventHandler(clientUploadStream_WriteStreamClosed);

Uri uri = new Uri(_urlStream + dialog.File.Name, UriKind.Absolute);

clientUploadStream.Headers["Content-Type"] = "multipart/form-data";

clientUploadStream.OpenWriteAsync(uri, "POST", fs);

}

void clientUploadStream_UploadProgressChanged(object sender, UploadProgressChangedEventArgs e)

{

// 因为是调用 OpenWriteAsync()，所以不会触发 UploadProgressChanged 事件

e.ProgressPercentage.ToString(),

e.BytesSent.ToString(),

e.TotalBytesToSend.ToString(),

e.BytesReceived.ToString(),

e.TotalBytesToReceive.ToString());

progressBarStream.Value = (double)e.ProgressPercentage;

}

void clientUploadStream_OpenWriteCompleted(object sender, OpenWriteCompletedEventArgs e)

{

System.Net.WebClient client = sender as System.Net.WebClient;

if (e.Error != null)

{

lblMsgStream.Text += e.Error.ToString();

return;

}

if (e.Cancelled != true)

{

// e.UserState - 需要上传的流（客户端流）

Stream clientStream = e.UserState as Stream;

// e.Result - 目标地址的流（服务端流）

Stream serverStream = e.Result;

byte[] buffer = new byte[4096];

int count = 0;

// clientStream.Read - 将需要上传的流读取到指定的字节数组中

while ((count = clientStream.Read(buffer, 0, buffer.Length)) > 0)

{

// serverStream.Write - 将指定的字节数组写入到目标地址的流

serverStream.Write(buffer, 0, count);

}

serverStream.Close();

clientStream.Close();

}

void clientUploadStream_WriteStreamClosed(object sender, WriteStreamClosedEventArgs e)

{

if (e.Error != null)

{

lblMsgStream.Text += e.Error.ToString();

return;

}

else

{

lblMsgStream.Text += "上传完成";

}

* 其他：

* 1、WebClient 对象一次只能启动一个请求。如果在一个请求完成（包括出错和取消）前，即IsBusy为true时，进行第二个请求，则第二个请求将会抛出 NotSupportedException 类型的异常

* 2、如果 WebClient 对象的 BaseAddress 属性不为空，则 BaseAddress 与 URI（相对地址）组合在一起构成绝对 URI

* 3、WebClient 类的 AllowReadStreamBuffering 属性：是否对从 Internet 资源接收的数据做缓冲处理。默认值为true，将数据缓存在客户端内存中，以便随时被应用程序读取

OK
[源码下载]

posted @ 2008-12-08 08:52 webabcd 阅读(9511) 评论(62) 编辑收藏举报

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