Silverlight实用窍门系列：32.WebClient上传String、下载String、上传Stream流、下载Stream流【附带源码实例】
Silverlight中我们很多时候需要上传下载数据的时候，在本节将讲述使用WebClient上传String、下载String、上传Stream流、下载Stream流的4个方法和相应的事件。下面我们首先认识一下WebClient类。
WebClient的主要函数如下：
•OpenReadAsync 打开流向指定资源的可读流。
•OpenWriteAsync 打开一个流以将数据写入指定的资源。这些方法不会阻止调用线程。
•DownloadStringAsync 以字符串形式下载位于指定 Uri 的资源。
•UploadStringAsync 将指定的字符串上载到指定的资源。这些方法不会阻止调用线程。
WebClient的主要事件如下：
•OpenReadCompleted 在异步资源读取操作完成时发生。
•OpenWriteCompleted 在打开流以将数据写入资源的异步操作完成时发生。
•DownloadStringCompleted 在异步资源下载操作完成时发生。
•DownloadProgressChanged 在异步下载操作成功传输部分或全部数据后发生。
•UploadStringCompleted 在异步字符串上载操作完成时发生。
•UploadProgressChanged 在异步上载操作成功转换部分或全部数据后发生。
上面的函数和事件在Silverlight的API中有详细的解释，在本文中不再复述。下面我们来看看一个实例来使用WebClient上传String、下载String、上传Stream流、下载Stream流。
首先我们准备XAML文件的前台代码，其内有四个按钮，分别代表上传String、下载String、上传Stream流、下载Stream流的按钮。代码如下：
<
Grid x:Name
=
"
LayoutRoot
"
Background
=
"
White
"
>
<
Canvas Name
=
"
lRoot
"
></
Canvas
>
<
Button Content
=
"
WebClient下载XAP
"
Height
=
"
23
"
HorizontalAlignment
=
"
Left
"
Margin
=
"
410,60,0,0
"
Name
=
"
button1
"
VerticalAlignment
=
"
Top
"
Width
=
"
178
"
Click
=
"
buttonOpenReadAsync_Click
"
/>
<
Button Content
=
"
DownloadStringAsync下载XML
"
Height
=
"
23
"
HorizontalAlignment
=
"
Left
"
Margin
=
"
410,100,0,0
"
Name
=
"
button2
"
VerticalAlignment
=
"
Top
"
Width
=
"
178
"
Click
=
"
buttonDownloadStringAsync_Click
"
/>
<
Button Content
=
"
UploadStringAsync上传String
"
Height
=
"
23
"
HorizontalAlignment
=
"
Left
"
Margin
=
"
410,140,0,0
"
Name
=
"
button3
"
VerticalAlignment
=
"
Top
"
Width
=
"
178
"
Click
=
"
buttonUploadStringAsync_Click
"
/>
<
Button Content
=
"
OpenWriteAsync上传图片
"
Height
=
"
23
"
HorizontalAlignment
=
"
Left
"
Margin
=
"
410,180,0,0
"
Name
=
"
button4
"
VerticalAlignment
=
"
Top
"
Width
=
"
178
"
Click
=
"
buttonOpenWriteAsync_Click
"
/>
</
Grid
>
•上传String操作如下：
首先建立一个TestHandle.ashx,向这个文件内部写入以下代码以接收Silverlight中上传的String字符。
///
<summary>
///
TestHandle 的摘要说明
///
</summary>
public
class
TestHandle : IHttpHandler
{
public
void
ProcessRequest(HttpContext context)
{
int
bytelength
=
context.Request.ContentLength;
byte
[] inputbytes
=
context.Request.BinaryRead(bytelength);
string
message
=
System.Text.Encoding.Default.GetString(inputbytes);
context.Response.ContentType
=
"
text/plain
"
;
context.Response.Write(
"
你已经提交数据：
"
+
message);
}
public
bool
IsReusable
{
get
{
return
false
;
}
}
}
我们再看Silverlight端代码如下：
#region
UploadStringAsync上传String
private
void
buttonUploadStringAsync_Click(
object
sender, RoutedEventArgs e)
{
//
开始调用UploadStringAsync异步上传String
Appclient.UploadStringAsync(
new
Uri(
"
http://localhost:3993/TestHandle.ashx
"
, UriKind.RelativeOrAbsolute),
"
<TD></TD>
"
);
Appclient.UploadStringCompleted
+=
new
UploadStringCompletedEventHandler(Appclient_UploadStringCompleted);
}
void
Appclient_UploadStringCompleted(
object
sender, UploadStringCompletedEventArgs e)
{
MessageBox.Show(e.Result);
Appclient.UploadStringCompleted
-=
new
UploadStringCompletedEventHandler(Appclient_UploadStringCompleted);
}
#endregion
•下载String操作如下：
下载ClientBin目录下已经存在的XML文件
#region
DownloadStringAsync下载XML
private
void
buttonDownloadStringAsync_Click(
object
sender, RoutedEventArgs e)
{
//
开始调用DownloadStringAsync异步下载文档并且读取它
Appclient.DownloadStringAsync(
new
Uri(
"
http://localhost:3993/ClientBin/222.xml
"
, UriKind.RelativeOrAbsolute));
Appclient.DownloadStringCompleted
+=
new
DownloadStringCompletedEventHandler(Appclient_DownloadStringCompleted);
}
void
Appclient_DownloadStringCompleted(
object
sender, DownloadStringCompletedEventArgs e)
{
MessageBox.Show(e.Result);
Appclient.DownloadStringCompleted
-=
new
DownloadStringCompletedEventHandler(Appclient_DownloadStringCompleted);
}
#endregion
•上传Stream操作如下：
建立一个AddFileHandle.ashx,向这个文件内部写入以下代码以接收Silverlight中上传的Stream数据流。
///
<summary>
///
AddFileHandle 的摘要说明
///
</summary>
public
class
AddFileHandle : IHttpHandler
{
public
void
ProcessRequest(HttpContext context)
{
//
获取上传的数据流
using
(Stream sr
=
context.Request.InputStream)
{
string
filename
=
"
Fir
"
;
byte
[] buffer
=
new
byte
[
4096
];
int
bytesRead
=
0
;
//
将当前数据流写入ClientBin文件下Fir.jpg文件中
using
(FileStream fs
=
File.Create(context.Server.MapPath(
"
ClientBin/
"
+
filename
+
"
.jpg
"
),
4096
))
{
while
((bytesRead
=
sr.Read(buffer,
0
, buffer.Length))
>
0
)
{
//
将数据写入文件
fs.Write(buffer,
0
, bytesRead);
}
}
}
}
public
bool
IsReusable
{
get
{
return
false
;
}
}
}
Silverlight读取图片数据，然后传到服务器端（注：此处没有验证传什么数据，如有需要自己调用OpenFileDialog.Filter即可），代码如下：
#region
OpenWriteAsync上传图片
private
void
buttonOpenWriteAsync_Click(
object
sender, RoutedEventArgs e)
{
OpenFileDialog dialog
=
new
OpenFileDialog();
if
(dialog.ShowDialog()
==
true
)
{
//
开始调用OpenWriteAsync方法上传数据
Appclient.OpenWriteAsync(
new
Uri(
"
http://localhost:3993/AddFileHandle.ashx
"
, UriKind.RelativeOrAbsolute),
"
POST
"
, dialog.File.OpenRead());
Appclient.OpenWriteCompleted
+=
new
OpenWriteCompletedEventHandler(Appclient_OpenWriteCompleted);
}
}
void
Appclient_OpenWriteCompleted(
object
sender, OpenWriteCompletedEventArgs e)
{
//
将图片数据流发送到服务器上
Stream inputStream
=
e.UserState
as
Stream;
Stream outputStream
=
e.Result;
byte
[] buffer
=
new
byte
[
4096
];
int
bytesRead
=
0
;
while
((bytesRead
=
inputStream.Read(buffer,
0
, buffer.Length))
>
0
)
{
outputStream.Write(buffer,
0
, bytesRead);
}
outputStream.Close();
inputStream.Close();
MessageBox.Show(
"
图片上传成功！
"
);
Appclient.OpenWriteCompleted
-=
new
OpenWriteCompletedEventHandler(Appclient_OpenWriteCompleted);
}
#endregion
•下载Stream操作如下：
本例采用上一节的源码，下载Stream流，然后反射为对象，源码如下：
#region
OpenReadAsync下载XAP
private
void
buttonOpenReadAsync_Click(
object
sender, RoutedEventArgs e)
{
//
1 •使用WebClient下载SLRandarHitTest.xap文件，进行异步读取。
Appclient.OpenReadAsync(
new
Uri(
"
SLRandarHitTest.xap
"
, UriKind.Relative));
Appclient.OpenReadCompleted
+=
new
OpenReadCompletedEventHandler(Appclient_OpenReadCompleted);
}
void
Appclient_OpenReadCompleted(
object
sender, OpenReadCompletedEventArgs e)
{
CreateXAPResource(
"
SLRandar.dll
"
,
"
SLRandar.MainPage
"
, e.Result);
Appclient.OpenReadCompleted
-=
new
OpenReadCompletedEventHandler(Appclient_OpenReadCompleted);
}
///
<summary>
///
创建XAP包的反射实例并且加装到Canvas中
///
</summary>
///
<param name="dllStr">
XAP包中的编译完成的运行代码的DLL文件
</param>
///
<param name="mainStr">
需要实例化的启动页面
</param>
///
<param name="resultStream">
使用WebClient下载到的数据流
</param>
private
void
CreateXAPResource(
string
dllStr,
string
mainStr, Stream resultStream)
{
//
3 •获取其他包提供的资源流信息
StreamResourceInfo streamResourceInfo
=
Application.GetResourceStream(
new
StreamResourceInfo(resultStream
as
Stream,
null
),
new
Uri(dllStr, UriKind.RelativeOrAbsolute));
//
4 •对Stream进行反射
AssemblyPart assemblyPart
=
new
AssemblyPart();
Assembly assembly
=
assemblyPart.Load(streamResourceInfo.Stream);
//
5 •(创建实例
var uc
=
(UserControl)assembly.CreateInstance(mainStr);
lRoot.Children.Clear();
lRoot.Children.Add(uc);
}
#endregion
本节实例采用VS2010+Silverlight 4.0编写。如需源码点击 SLWebClient.rar 下载。