（13）：Silverlight 2 数据与通信之WebRequest_app

概述概述 Silverlight 2 Beta 1版本发布了，无论从Runtime还是Tools都给我们带来了很多的惊喜，如支持框架语言Visual Basic, Visual C#, IronRuby, Ironpython，对JSON、Web Service、WCF以及Sockets的支持等一系列新的特性。《一步一步学Silverlight 2系列》文章带您快速进入Silverlight 2开发。概述 Silverlight 2 Beta 1版本发布了，无论从Runtime还是Tools都给我们带来了很多的惊喜，如支持框架语言Visual Basic,Visual C#,IronRuby,Ironpython，对JsON、Web Service、WCF以及Sockets的支持等一系列新的特性。《一步一步学Silverlight 2系列》文章带您快速进入Silverlight 2开发。本文将简单介绍在Silverlight 2中如何使用WebRequest进行数据的提交和获取。简单示例在本文中，我们仍然使用在一步一步学Silverlight 2系列（12）：数据与通信之WebClient中用过的示例，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。最终运行的结果如下图：

编写界面布局，XAML如下：

<GrID Background="#46461F">    <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">        <TextBlock x:name="lblPrice" Text="价格：" Foreground="White"                   HorizontalAlignment="left" VerticalAlignment="Center"                   margin="20 0 0 0"></TextBlock>    </border></GrID>

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：

public class BookHandler : 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，关于数据绑定可以参考一步一步学Silverlight 2系列（11）：数据绑定。

private voID UserControl_Loaded(object sender,RoutedEventArgs e){    List<Book> books = new List<Book>() {         new Book("Professional ASP.NET 3.5"),new Book("ASP.NET AJAX In Action"),new Book("Silverlight In Action"),new Book("ASP.NET 3.5 Unleashed"),new Book("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;voID Books_SelectionChanged(object sender,SelectionChangedEventArgs e){    bookNo = Books.Selectedindex.ToString();    Uri endpoint = new Uri("http://localhost:49955/BookHandler.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。

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();    }}

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();    }}