(13):Silverlight 2 数据与通信之WebRequest

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:
(13):Silverlight 2 数据与通信之WebRequest 
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();

    }

}
最后运行的结果如下:
(13):Silverlight 2 数据与通信之WebRequest 
用户选择一本书籍后,将显示其价格:
(13):Silverlight 2 数据与通信之WebRequest 

结束语

本文简单介绍了在Silverlight 2中如何使用WebRequest提交和获取数据,你可以从 这里下载示例程序。

本文出自 “TerryLee技术专栏” 博客,请务必保留此出处http://terrylee.blog.51cto.com/342737/67250

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