silverlight 4数据与通信之WebRequest详解
此篇博文基于《silverlight4数据与通信之WebClient详解 silverlight4版》，查看请请点击这里
这里用上一篇文章用过的示例，只不过稍微做一点小的改动，使用 WebRequest 提交书籍编号数据，并根据书籍号返回价格信息。
<
TextBlock
x:Name
="lblPrice"
Text
="价格："
Foreground
="White"
HorizontalAlignment
="Left"
VerticalAlignment
="Center"
Margin
="20 0 0 0"
></
TextBlock
>
</
Border
>
</
Grid
>
<
Grid.RowDefinitions
>
<
RowDefinition
Height
="40"
></
RowDefinition
>
<
RowDefinition
Height
="*"
></
RowDefinition
>
<
RowDefinition
Height
="40"
></
RowDefinition
>
</
Grid.RowDefinitions
>
<
Grid.ColumnDefinitions
>
<
ColumnDefinition
></
ColumnDefinition
>
</
Grid.ColumnDefinitions
>
<
Border
Grid.Row
="0"
Grid.Column
="0"
CornerRadius
="15"
Width
="240"
Height
="36"
Margin
="20 0 0 0"
HorizontalAlignment
="Left"
>
<
TextBlock
Text
="书籍列表"
Foreground
="White"
HorizontalAlignment
="Left"
VerticalAlignment
="Center"
Margin
="20 0 0 0"
></
TextBlock
>
</
Border
>
<
ListBox
x:Name
="Books"
Grid.Row
="1"
Margin
="40 10 10 10"
SelectionChanged
="Books_SelectionChanged"
>
<
ListBox.ItemTemplate
>
<
DataTemplate
>
<
StackPanel
>
<
TextBlock
Text
="
{Binding Name}
"
Height
="32"
></
TextBlock
>
</
StackPanel
>
</
DataTemplate
>
</
ListBox.ItemTemplate
>
</
ListBox
>
<
Border
Grid.Row
="2"
Grid.Column
="0"
CornerRadius
="15"
Width
="240"
Height
="36"
Background
="Orange"
Margin
="20 0 0 0"
HorizontalAlignment
="Left"
>
<
Grid
Background
="#46461F"
>
编写 HttpHandler，注意我使用了 context.Request.Form["No"]，在后面我们将使用 WebRequest
在 RequestReady 方法中将数据写入请求流：
using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Web;
namespace
sample.Web
{
///
<summary>
///
BookHandler2 的摘要说明
///
</summary>
public
class
BookHandler2 : IHttpHandler
{
public
static
readonly
string
[] PriceList
=
new
string
[] {
"
66.00
"
,
"
78.30
"
,
"
56.50
"
,
"
28.80
"
,
"
77.00
"
};
public
void
ProcessRequest(HttpContext context)
{
context.Response.ContentType
=
"
text/plain
"
;
context.Response.Write(PriceList[Int32.Parse(context.Request.Form[
"
No
"
])]);
}
public
bool
IsReusable
{
get
{
return
false
;
}
}
}
}
在界面加载时绑定书籍列表
private
void
UserControl_Loaded(
object
sender, RoutedEventArgs e)
{
List
<
BookClass
>
books
=
new
List
<
BookClass
>
()
{
new
BookClass(
"
Professional ASP.NET 3.5
"
),
new
BookClass(
"
ASP.NET AJAX In Action
"
),
new
BookClass(
"
Silverlight In Action
"
),
new
BookClass(
"
ASP.NET 3.5 Unleashed
"
),
new
BookClass(
"
Introducing Microsoft ASP.NET AJAX
"
)
};
Books.ItemsSource
=
books;
}
接下来在 SelectionChanged 事件中实现用户选择书籍时，我们使用 WebRequest 提交书籍编号，并且
获得价格数据，仍然采用异步模式，提供 RequestReady和 ResponseReady 两个回调函数：
private
string
bookNo;
private
void
Books_SelectionChanged(
object
sender, SelectionChangedEventArgs e)
{
bookNo
=
Books.SelectedIndex.ToString();
//
端口可根据自己的情况随便更改
Uri endpoint
=
new
Uri(String.Format(
"
http://localhost:80/BookHandler2.ashx
"
));
WebRequest request
=
WebRequest.Create(endpoint);
request.Method
=
"
POST
"
;
request.ContentType
=
"
application/x-www-form-urlencoded
"
;
request.BeginGetRequestStream(
new
AsyncCallback(RequestReady), request);
//
request.BeginGetResponse(new AsyncCallback(ResponseReady), request);
}
实现 RequestReady 方法，将书籍的编号写入请求流中。要注意添加System.IO命名空间。
void
RequestReady(IAsyncResult asyncResult)
{
WebRequest request
=
asyncResult.AsyncState
as
WebRequest;
Stream requestStream
=
request.EndGetRequestStream(asyncResult);
using
(StreamWriter writer
=
new
StreamWriter(requestStream))
{
writer.Write(String.Format(
"
No={0}
"
, bookNo));
writer.Flush();
}
request.BeginGetResponse(
new
AsyncCallback(ResponseReady), request);
}
实现 ResponseReady 方法，显示返回的结果。
void
ResponseReady(IAsyncResult asyncResult)
{
WebRequest request
=
asyncResult.AsyncState
as
WebRequest;
WebResponse response
=
request.EndGetResponse(asyncResult);
using
(Stream responseStream
=
response.GetResponseStream())
{
StreamReader reader
=
new
StreamReader(responseStream);
//
lblPrice.Text = "价格：" + reader.ReadToEnd();
//
lblPrice.Dispatcher.BeginInvoke(new UpdatePriceDelegate(UpdatePrice), reader.ReadToEnd());
//
‘charleslau’的方法，可以运行
string
price
=
reader.ReadToEnd();
if
(
this
.lblPrice.CheckAccess())
{
this
.lblPrice.Text
=
"
价格:
"
+
price;
}
else
{
this
.Dispatcher.BeginInvoke(
new
UIContextChangedEventHandler(UIContextChanged), price);
}
}
}
public
delegate
void
UIContextChangedEventHandler(
object
state);
private
void
UIContextChanged(
object
state)
{
this
.lblPrice.Text
=
"
价格:
"
+
(String)state;
}
至此，大功告成，可以访问了，效果参见上一篇博文，文中有很多注释的地方，那是我参考的实例是silverlight2beta版测试通过的，在silverlight4中有些许不同，我已经做了修改，代码测试可以通过。下面附加后台完整代码
完整后台代码
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
sample
{
public
partial
class
s13 : UserControl
{
public
s13()
{
InitializeComponent();
}
private
void
UserControl_Loaded(
object
sender, RoutedEventArgs e)
{
List
<
BookClass
>
books
=
new
List
<
BookClass
>
()
{
new
BookClass(
"
Professional ASP.NET 3.5
"
),
new
BookClass(
"
ASP.NET AJAX In Action
"
),
new
BookClass(
"
Silverlight In Action
"
),
new
BookClass(
"
ASP.NET 3.5 Unleashed
"
),
new
BookClass(
"
Introducing Microsoft ASP.NET AJAX
"
)
};
Books.ItemsSource
=
books;
}
private
string
bookNo;
private
void
Books_SelectionChanged(
object
sender, SelectionChangedEventArgs e)
{
bookNo
=
Books.SelectedIndex.ToString();
//
端口可根据自己的情况随便更改
Uri endpoint
=
new
Uri(String.Format(
"
http://localhost:80/BookHandler2.ashx
"
));
WebRequest request
=
WebRequest.Create(endpoint);
request.Method
=
"
POST
"
;
request.ContentType
=
"
application/x-www-form-urlencoded
"
;
request.BeginGetRequestStream(
new
AsyncCallback(RequestReady), request);
//
request.BeginGetResponse(new AsyncCallback(ResponseReady), request);
}
void
RequestReady(IAsyncResult asyncResult)
{
WebRequest request
=
asyncResult.AsyncState
as
WebRequest;
Stream requestStream
=
request.EndGetRequestStream(asyncResult);
using
(StreamWriter writer
=
new
StreamWriter(requestStream))
{
writer.Write(String.Format(
"
No={0}
"
, bookNo));
writer.Flush();
}
request.BeginGetResponse(
new
AsyncCallback(ResponseReady), request);
}
void
ResponseReady(IAsyncResult asyncResult)
{
WebRequest request
=
asyncResult.AsyncState
as
WebRequest;
WebResponse response
=
request.EndGetResponse(asyncResult);
using
(Stream responseStream
=
response.GetResponseStream())
{
StreamReader reader
=
new
StreamReader(responseStream);
//
lblPrice.Text = "价格：" + reader.ReadToEnd();
//
lblPrice.Dispatcher.BeginInvoke(new UpdatePriceDelegate(UpdatePrice), reader.ReadToEnd());
//
‘charleslau’的方法，可以运行
string
price
=
reader.ReadToEnd();
if
(
this
.lblPrice.CheckAccess())
{
this
.lblPrice.Text
=
"
价格:
"
+
price;
}
else
{
this
.Dispatcher.BeginInvoke(
new
UIContextChangedEventHandler(UIContextChanged), price);
}
}
}
public
delegate
void
UIContextChangedEventHandler(
object
state);
private
void
UIContextChanged(
object
state)
{
this
.lblPrice.Text
=
"
价格:
"
+
(String)state;
}
//
private void UpdatePrice(string price)
//
{
//
lblPrice.Text = "price:" + price;
//
}
//
private delegate void UpdatePriceDelegate(string price);
}
}
感谢李老师和回帖的前辈，我对数据通信知之甚少，如有纰漏，敬请指出