一步一步学Silverlight 2系列（12）：数据与通信之WebClient

心已赠人 2021-12-17 05:43 257阅读 0赞

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 版权声明：原创作品，允许转载，转载时请务必以超链接形式标明文章 
 <a style="text-decoration:underline;" href="http://terrylee.blog.51cto.com/342737/67249" rel="nofollow">原始出处</a> 、作者信息和本声明。否则将追究法律责任。 
 <a href="http://terrylee.blog.51cto.com/342737/67249" rel="nofollow">http://terrylee.blog.51cto.com/342737/67249</a> 
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 <h2>概述</h2> 
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 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。 
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 本文将介绍如何在Silverlight 2中使用Web Client进行通信。 
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 <h2>简单示例</h2> 
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 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： 
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 <div> 
 <a href="https://images.cnblogs.com/cnblogs_com/Terrylee/WindowsLiveWriter/Silverlight212Silverlight_599/TerryLee_Silverlight2_0059_2.gif" rel="nofollow"></a> 
 <img alt="" src="http://terrylee.blog.51cto.com/attachment/200803/200803241206347274765.gif">&nbsp; 
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 编写界面布局，XAML如下： 
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 <pre>&lt;Grid Background="#46461F"&gt;
 &lt;Grid.RowDefinitions&gt;
 &lt;RowDefinition Height="40"&gt;&lt;/RowDefinition&gt;
 &lt;RowDefinition Height="*"&gt;&lt;/RowDefinition&gt;
 &lt;RowDefinition Height="40"&gt;&lt;/RowDefinition&gt;
 &lt;/Grid.RowDefinitions&gt;
 &lt;Grid.ColumnDefinitions&gt;
 &lt;ColumnDefinition&gt;&lt;/ColumnDefinition&gt;
 &lt;/Grid.ColumnDefinitions&gt;
 &lt;Border Grid.Row="0" Grid.Column="0" CornerRadius="15"
 Width="240" Height="36"
 Margin="20 0 0 0" HorizontalAlignment="Left"&gt;
 &lt;TextBlock Text="书籍列表" Foreground="White"
 HorizontalAlignment="Left" VerticalAlignment="Center"
 Margin="20 0 0 0"&gt;&lt;/TextBlock&gt;
 &lt;/Border&gt;
 &lt;ListBox x:Name="Books" Grid.Row="1" Margin="40 10 10 10"
 SelectionChanged="Books_SelectionChanged"&gt;
 &lt;ListBox.ItemTemplate&gt;
 &lt;DataTemplate&gt;
 &lt;StackPanel&gt;
 &lt;TextBlock Text="{
 Binding Name}" Height="32"&gt;&lt;/TextBlock&gt;
 &lt;/StackPanel&gt;
 &lt;/DataTemplate&gt;
 &lt;/ListBox.ItemTemplate&gt;
 &lt;/ListBox&gt;
 &lt;Border Grid.Row="2" Grid.Column="0" CornerRadius="15"
 Width="240" Height="36" Background="Orange"
 Margin="20 0 0 0" HorizontalAlignment="Left"&gt;
 &lt;TextBlock x:Name="lblPrice" Text="价格：" Foreground="White"
 HorizontalAlignment="Left" VerticalAlignment="Center"
 Margin="20 0 0 0"&gt;&lt;/TextBlock&gt;
 &lt;/Border&gt;
 &lt;/Grid&gt;</pre> 
 <div> 
 <a href="http://11011.net/software/vspaste" rel="nofollow"></a>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： 
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 <pre>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;
 }
 }
 }</pre> 
 <a href="http://11011.net/software/vspaste" rel="nofollow"></a> 
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 在界面加载时绑定书籍列表，关于数据绑定可以参考 
 <a href="http://www.cnblogs.com/Terrylee/archive/2008/03/08/Silverlight2-step-by-step-part11-Data-Binding.html" rel="nofollow">一步一步学Silverlight 2系列（11）：数据绑定</a>。 
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 <pre>void UserControl_Loaded(object sender, RoutedEventArgs e)
 {
 List&lt;Book&gt; books = new List&lt;Book&gt;() {
 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;
 }</pre> 
 <a href="http://11011.net/software/vspaste" rel="nofollow"></a> 
 <div>
 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。 
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 <pre>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;
 }
 }</pre> 
 <a href="http://11011.net/software/vspaste" rel="nofollow"></a> 
 <a href="http://11011.net/software/vspaste" rel="nofollow"></a> 
 <div>
 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： 
 </div> 
 <div> 
 <a href="https://images.cnblogs.com/cnblogs_com/Terrylee/WindowsLiveWriter/Silverlight212Silverlight_599/TerryLee_Silverlight2_0060_2.gif" rel="nofollow"></a> 
 <img alt="" src="http://terrylee.blog.51cto.com/attachment/200803/200803241206347289796.gif">&nbsp; 
 </div> 
 <div>
 最后完整的代码如下： 
 </div> 
 <pre>public partial class Page : UserControl
 {
 public Page()
 {
 InitializeComponent();
 }
 void UserControl_Loaded(object sender, RoutedEventArgs e)
 {
 List&lt;Book&gt; books = new List&lt;Book&gt;() {
 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;
 }
 }
 }</pre> 
 <a href="http://11011.net/software/vspaste" rel="nofollow"></a> 
 <div> 
 <a href="http://11011.net/software/vspaste" rel="nofollow"></a>运行后效果如下： 
 </div> 
 <div> 
 <a href="https://images.cnblogs.com/cnblogs_com/Terrylee/WindowsLiveWriter/Silverlight212Silverlight_599/TerryLee_Silverlight2_0059_2.gif" rel="nofollow"></a> 
 <img alt="" src="http://terrylee.blog.51cto.com/attachment/200803/200803241206347300421.gif">&nbsp; 
 </div> 
 <div>
 当我们选择其中一本书籍时，将会显示出它的价格： 
 </div> 
 <div> 
 <a href="https://images.cnblogs.com/cnblogs_com/Terrylee/WindowsLiveWriter/Silverlight212Silverlight_599/TerryLee_Silverlight2_0061_4.gif" rel="nofollow"></a> 
 <img alt="" src="http://terrylee.blog.51cto.com/attachment/200803/200803241206347311828.gif">&nbsp; 
 </div> 
 <h2>结束语</h2> 
 <div>
 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 
 <a href="http://files.cnblogs.com/Terrylee/TerryLee.SilverlightDemo25.rar" rel="nofollow">这里</a>下载本文示例代码。 
 </div> 
 本文出自 “<a href="http://terrylee.blog.51cto.com/" rel="nofollow">TerryLee技术专栏</a>” 博客，请务必保留此出处<a href="http://terrylee.blog.51cto.com/342737/67249" rel="nofollow">http://terrylee.blog.51cto.com/342737/67249</a> 
 <a href="http://terrylee.blog.51cto.com/342737/67249" rel="nofollow">本文出自 51CTO.COM技术博客</a> 
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转载于:https://www.cnblogs.com/hdjjun/archive/2008/12/24/1361491.html