概述
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();
}
}
最后运行的结果如下:
用户选择一本书籍后,将显示其价格:
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。