(12):Silverlight 2 数据与通信之WebClient

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。
本文将介绍如何在Silverlight 2中使用Web Client进行通信。

简单示例

编写一个简单的示例,在该示例中,选择一本书籍之后,我们通过Web Client去查询书籍的价格,并显示出来,最终的效果如下:
(12):Silverlight 2 数据与通信之WebClient 
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>
为了模拟查询价格,我们编写一个HttpHandler,接收书籍的No,并返回价格:
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.QueryString["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
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;

    

}
接下来当用户选择一本书籍时,需要通过Web Client去获取书籍的价格,在Silverlight 2中,所有的网络通信API都设计为了异步模式。在声明一个Web Client实例后,我们需要为它注册DownloadStringCompleted事件处理方法,在下载完成后将会被回调,然后再调用DownloadStringAsync方法开始下载。
void Books_SelectionChanged(object sender, SelectionChangedEventArgs e)

{

    Uri endpoint = new Uri(String.Format("http://localhost:49955/BookHandler.ashx?No={0}",Books.SelectedIndex));

    WebClient client = new WebClient();

    client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);

    

    client.DownloadStringAsync(endpoint);

}

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)

{

    if (e.Error == null)

    {

        lblPrice.Text = "价格:" + e.Result;

    }

    else

    {

        lblPrice.Text = e.Error.Message;

    }

}
注意大家可以在Web Application Project的属性页中,把ASP.NET Development Server的端口号设置为一个固定的端口号:
(12):Silverlight 2 数据与通信之WebClient 
最后完整的代码如下:
public partial class Page : UserControl

{

    public Page()

    {

        InitializeComponent();

    }

    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;

        

    }

    void Books_SelectionChanged(object sender, SelectionChangedEventArgs e)

    {

        Uri endpoint = new Uri(String.Format("http://localhost:49955/BookHandler.ashx?No={0}",Books.SelectedIndex));

        WebClient client = new WebClient();

        client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);

        

        client.DownloadStringAsync(endpoint);

    }

    void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)

    {

        if (e.Error == null)

        {

            lblPrice.Text = "价格:" + e.Result;

        }

        else

        {

            lblPrice.Text = e.Error.Message;

        }

    }

}
运行后效果如下:
(12):Silverlight 2 数据与通信之WebClient 
当我们选择其中一本书籍时,将会显示出它的价格:
(12):Silverlight 2 数据与通信之WebClient 

结束语

本文简单介绍了Silverlight 2中使用Web Client进行通信的知识,在Silverlight 2中,提供的通信API非常丰富,后面将会介绍其他的方式。你可以从 这里下载本文示例代码。

本文出自 “TerryLee技术专栏” 博客,请务必保留此出处http://terrylee.blog.51cto.com/342737/67249

你可能感兴趣的:(silverlight)