silverlight: http请求的GET及POST示例

http请求的get/post并不是难事，只是silverlight中一切皆是异步，所以代码看起来就显得有些冗长了，下面这个HttpHelper是在总结 园友 的基础上，修改得来：

 namespace SLAwb.Helper
 {
     public sealed class MediaType
     {
         /// <summary>
         /// "application/xml"
         /// </summary>
         public const string APPLICATION_XML = "application/xml";

         /// <summary>
         /// application/json
         /// </summary>
         public const string APPLICATION_JSON = "application/json";

         /// <summary>
         /// "application/x-www-form-urlencoded"
         /// </summary>
         public const string APPLICATION_FORM_URLENCODED = "application/x-www-form-urlencoded";

     }
 }

 using System;
 using System.IO;
 using System.Net;
 using System.Threading;

 namespace SLAwb.Helper
 {
     /// <summary>
     /// Http工具类，用于向指定url发起Get或Post请求
     /// http://yjmyzz.cnblogs.com/
     /// </summary>
     public class HttpHelper
     {
         private string postData;
         SynchronizationContext currentContext;
         SendOrPostCallback sendOrPostCallback;

         /// <summary>
         /// 从指定url以Get方式获取数据
         /// </summary>
         /// <param name="url"></param>
         /// <param name="completedHandler"></param>
         public void Get(string url, DownloadStringCompletedEventHandler completedHandler)
         {
             WebClient client = new WebClient();
             client.DownloadStringCompleted += completedHandler;
             client.DownloadStringAsync(new Uri(url));
         }

         /// <summary>
         /// 向指定url地址Post数据
         /// </summary>
         /// <param name="url"></param>
         /// <param name="data"></param>
         /// <param name="mediaType"></param>
         /// <param name="synchronizationContext"></param>
         /// <param name="callBack"></param>
         public void Post(string url, string data, string mediaType, SynchronizationContext synchronizationContext, SendOrPostCallback callBack)
         {
             currentContext = synchronizationContext;
             Uri endpoint = new Uri(url);
             sendOrPostCallback = callBack;
             HttpWebRequest request = (HttpWebRequest)WebRequest.Create(endpoint);
             request.Method = "POST";
             request.ContentType = mediaType;
             postData = data;
             request.BeginGetRequestStream(new AsyncCallback(RequestReadySocket), request);
         }

         private void RequestReadySocket(IAsyncResult asyncResult)
         {
             WebRequest request = asyncResult.AsyncState as WebRequest;
             Stream requestStream = request.EndGetRequestStream(asyncResult);

             using (StreamWriter writer = new StreamWriter(requestStream))
             {
                 writer.Write(postData);
                 writer.Flush();
             }

             request.BeginGetResponse(new AsyncCallback(ResponseReadySocket), request);
         }

         private void ResponseReadySocket(IAsyncResult asyncResult)
         {
             try
             {
                 WebRequest request = asyncResult.AsyncState as WebRequest;
                 WebResponse response = request.EndGetResponse(asyncResult);
                 using (Stream responseStream = response.GetResponseStream())
                 {
                     StreamReader reader = new StreamReader(responseStream);
                     string paramStr = reader.ReadToEnd();
                     currentContext.Post(sendOrPostCallback, paramStr);
                 }
             }
             catch (Exception e)
             {
                 currentContext.Post(sendOrPostCallback, e.Message);
             }

         }

     }
 }

Silverlight中的测试代码：
xaml部分

 <UserControl x:Class="SLAwb.MainPage"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     mc:Ignorable="d"
     d:DesignHeight="480" d:DesignWidth="640">

     <Grid x:Name="LayoutRoot" Background="White">
         <Grid.RowDefinitions>
             <RowDefinition Height="30"></RowDefinition>
             <RowDefinition Height="*"></RowDefinition>
             <RowDefinition Height="2*"></RowDefinition>
         </Grid.RowDefinitions>
         <Grid Grid.Row="0" Margin="3">
             <Grid.ColumnDefinitions>
                 <ColumnDefinition Width="40"></ColumnDefinition>
                 <ColumnDefinition Width="*"></ColumnDefinition>
                 <ColumnDefinition Width="75"></ColumnDefinition>
                 <ColumnDefinition Width="95"></ColumnDefinition>
                 <ColumnDefinition Width="80"></ColumnDefinition>
                 <ColumnDefinition Width="80"></ColumnDefinition>
             </Grid.ColumnDefinitions>
             <TextBlock VerticalAlignment="Center" TextAlignment="Right">地址：</TextBlock>
             <TextBox Name="txtUrl" Grid.Column="1" Text="http://localhost/"></TextBox>
             <TextBlock Grid.Column="2" VerticalAlignment="Center" TextAlignment="Right">MediaType：</TextBlock>
             <TextBox Name="txtMediaType" Grid.Column="3" Text="application/xml"></TextBox>
             <Button Name="btnPost" Content="Post" Grid.Column="4" Margin="3,1" Click="btnPost_Click"></Button>
             <Button Name="btnGet" Content="Get" Grid.Column="5" Margin="3,1" Click="btnGet_Click"></Button>
         </Grid>

         <Grid Grid.Row="1">
             <Grid.ColumnDefinitions>
                 <ColumnDefinition Width="40"></ColumnDefinition>
                 <ColumnDefinition Width="*"></ColumnDefinition>
             </Grid.ColumnDefinitions>
             <TextBlock VerticalAlignment="Top" TextAlignment="Right">数据：</TextBlock>
             <TextBox Name="txtPostData" Grid.Column="1" Margin="3" AcceptsReturn="True" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto"></TextBox>
         </Grid>

         <Grid Grid.Row="2">
             <Grid.ColumnDefinitions>
                 <ColumnDefinition Width="40"></ColumnDefinition>
                 <ColumnDefinition Width="*"></ColumnDefinition>
             </Grid.ColumnDefinitions>
             <TextBlock VerticalAlignment="Top" TextAlignment="Right">返回：</TextBlock>
             <TextBox Name="txtResult" Grid.Column="1" Margin="3" AcceptsReturn="True" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto"></TextBox>
         </Grid>
     </Grid>
 </UserControl>

cs部分

 using SLAwb.Helper;
 using System;
 using System.Net;
 using System.Threading;
 using System.Windows;
 using System.Windows.Controls;

 namespace SLAwb
 {
     public partial class MainPage : UserControl
     {
         private SynchronizationContext currentContext;

         public MainPage()
         {
             InitializeComponent();
             this.currentContext = SynchronizationContext.Current;
         }

         private void btnPost_Click(object sender, RoutedEventArgs e)
         {
             BeforeReturn();
             HttpHelper httpHelper = new HttpHelper();
             httpHelper.Post(txtUrl.Text, txtPostData.Text, txtMediaType.Text, currentContext, PostCompletedHandler);
         }

         private void PostCompletedHandler(Object obj)
         {
             txtResult.Text = obj.ToString();
         }

         private void btnGet_Click(object sender, RoutedEventArgs e)
         {
             BeforeReturn();
             HttpHelper httpHelper = new HttpHelper();
             httpHelper.Get(txtUrl.Text, GetCompletedHandler);
         }

         void BeforeReturn() {
             txtResult.Text = "loading...";
         }

         void GetCompletedHandler(object sender, DownloadStringCompletedEventArgs e)
         {
             if (e.Error == null)
             {
                 txtResult.Text = e.Result;
             }
             else
             {
                 txtResult.Text = e.Error.Message;
             }
         }
     }
 }