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稳扎稳打Silverlight(21) - 2.0通信之WebRequest和WebResponse, 对指定的URI发出请求以及接收响应


作者:webabcd


介绍
Silverlight 2.0 详解WebRequest和WebResponse,对指定的URI做GET和POST请求,以及接收其响应
    HttpWebRequest - 对指定的 URI 发出请求
        Create() - 初始化一个 WebRequest
        BeginGetResponse() - 开始对指定 URI 资源做异步请求
        EndGetResponse() - 结束对指定 URI 资源做异步请求
    HttpWebResponse - 对指定的 URI 做出响应
        GetResponseStream() - 获取响应的数据流


在线DEMO
http://www.cnblogs.com/webabcd/archive/2008/10/09/1307486.html


示例
1、对指定的URI做GET请求以及接收响应
WebRequestGet.xaml
<UserControl x:Class="Silverlight20.Communication.WebRequestGet"
    xmlns
="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x
="http://schemas.microsoft.com/winfx/2006/xaml">
    
<StackPanel HorizontalAlignment="Left" Margin="5">
    
        
<TextBlock x:Name="lblMsg" />
        
    
</StackPanel>
</UserControl>

WebRequestGet.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.Threading;
using System.IO;

namespace Silverlight20.Communication
{
    
public partial class WebRequestGet : UserControl
    
{
        
// 接收 GET 方式数据的 REST 服务
        string _url = "http://localhost:3036/REST.svc/Users/json";

        
// 异常信息
        string _exception = "";
        
        
// SynchronizationContext - 同步上下文管理类
        SynchronizationContext _syncContext;

        
public WebRequestGet()
        
{
            InitializeComponent();

            Demo();
        }


        
void Demo()
        
{
            
// SynchronizationContext.Current - 当前线程的同步上下文
            _syncContext = SynchronizationContext.Current;

            
/*
             * HttpWebRequest - 对指定的 URI 发出请求
             *     HttpWebRequest.Create(uri) - 初始化一个 WebRequest
             *     HttpWebRequest.BeginGetResponse(AsyncCallback callback, Object state) - 开始对指定 URI 资源做异步请求
             *         AsyncCallback callback - System.AsyncCallback 委托。异步操作完成时调用的回调方法
             *         Object state - 包含此异步请求的对象。即相应的 HttpWebRequest 对象
             *     HttpWebRequest.Abort() - 取消该异步请求
             *     HttpWebRequest.Accept - HTTP 头的 Accept  部分
             *     HttpWebRequest.ContentType - HTTP 头的 ContentType 部分
             *     HttpWebRequest.Headers - HTTP 头的 key/value 对集合
             *     HttpWebRequest.Method - HTTP 方法(只支持GET和POST)
             *     HttpWebRequest.RequestUri - 所请求的 URI
             *     HttpWebRequest.HaveResponse - 是否接收到了指定 URI 的响应
             *     HttpWebRequest.AllowReadStreamBuffering - 是否对从 Internet 资源接收的数据做缓冲处理。默认值为true,将数据缓存在客户端内存中,以便随时被应用程序读取
             
*/


            HttpWebRequest request 
= WebRequest.Create(
                
new Uri(_url, UriKind.Absolute)) as HttpWebRequest;
            request.Method 
= "GET";
            request.BeginGetResponse(
new AsyncCallback(ResponseCallback), request);
        }


        
private void ResponseCallback(IAsyncResult result)
        
{
            
// IAsyncResult.AsyncState - AsyncCallback 传过来的对象
            HttpWebRequest request = result.AsyncState as HttpWebRequest;

            WebResponse response 
= null;

            
try
            
{
                
// HttpWebRequest.EndGetResponse(IAsyncResult) - 结束对指定 URI 资源做异步请求
                
//     返回值为 WebResponse 对象
                response = request.EndGetResponse(result) as HttpWebResponse;
            }

            
catch (Exception ex)
            
{
                _exception 
= ex.ToString();
            }


            
// SynchronizationContext.Post(SendOrPostCallback d, Object state) - 将异步消息发送到该同步上下文中
            
//     SendOrPostCallback d - System.Threading.SendOrPostCallback 委托
            
//     Object state - 需要传递的参数
            _syncContext.Post(GetResponse, response);
        }


        
private void GetResponse(object state)
        
{
            
/*
             * HttpWebResponse - 对指定的 URI 做出响应
             *     GetResponseStream() - 获取响应的数据流
             
*/


            HttpWebResponse response 
= state as HttpWebResponse;

            
if (response != null)
            
{
                Stream responseStream 
= response.GetResponseStream();
                
using (StreamReader sr = new StreamReader(responseStream))
                
{
                    lblMsg.Text 
= sr.ReadToEnd();
                }

            }

            
else
            
{
                lblMsg.Text 
= _exception;
            }

        }

    }

}



2、对指定的URI做POST请求以及接收响应
WebRequestPost.xaml
<UserControl x:Class="Silverlight20.Communication.WebRequestPost"
    xmlns
="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x
="http://schemas.microsoft.com/winfx/2006/xaml">
    
<StackPanel HorizontalAlignment="Left" Margin="5">
    
        
<TextBlock x:Name="lblMsg" />
    
    
</StackPanel>
</UserControl>

WebRequestPost.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.Threading;
using System.IO;

namespace Silverlight20.Communication
{
    
public partial class WebRequestPost : UserControl
    
{
        
// 接收 POST 方式数据的 REST 服务
        string _url = "http://localhost:3036/REST.svc/PostUser";

        
// 异常信息
        string _exception = "";

        
// SynchronizationContext - 同步上下文管理类
        SynchronizationContext _syncContext;

        
public WebRequestPost()
        
{
            InitializeComponent();

            Demo();
        }


        
void Demo()
        
{
            _syncContext 
= SynchronizationContext.Current;

            HttpWebRequest request 
= WebRequest.Create(
                
new Uri(_url, UriKind.Absolute)) as HttpWebRequest;

            request.Method 
= "POST";

            
// BeginGetRequestStream(AsyncCallback callback, Object state) - 向指定的 URI 资源发送数据的流的异步请求
            
//     AsyncCallback callback - System.AsyncCallback 委托
            
//     Object state - 包含此异步请求的对象。即相应的 HttpWebRequest 对象
            IAsyncResult asyncResult = request.BeginGetRequestStream(
                
new AsyncCallback(RequestStreamCallback), request);
        }


        
private void RequestStreamCallback(IAsyncResult result)
        
{
            HttpWebRequest request 
= result.AsyncState as HttpWebRequest;
            request.ContentType 
= "application/x-www-form-urlencoded";

            
// HttpWebRequest.EndGetRequestStream(IAsyncResult) - 返回用于将数据写入某 URI 资源的 Stream
            Stream requestStream = request.EndGetRequestStream(result);

            StreamWriter streamWriter 
= new StreamWriter(requestStream);

            
// byte[] postdata = System.Text.Encoding.UTF8.GetBytes("name=webabcd");
            
// 多个参数用“&”分隔
            streamWriter.Write("name=webabcd");

            streamWriter.Close();

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


        
private void ResponseCallback(IAsyncResult result)
        
{
            HttpWebRequest request 
= result.AsyncState as HttpWebRequest;

            WebResponse response 
= null;

            
try
            
{
                response 
= request.EndGetResponse(result);
            }

            
catch (Exception ex)
            
{
                _exception 
= ex.ToString();
            }


            
// 调用 UI 线程
            _syncContext.Post(GetResponse, response);
        }


        
private void GetResponse(object state)
        
{
            
/*
             * HttpWebResponse - 对指定的 URI 做出响应
             *     GetResponseStream() - 获取响应的数据流
             *     ContentLength - 接收的数据的内容长度
             *     ContentType - HTTP 头的 ContentType 部分
             *     Method - HTTP 方法
             *     ResponseUri - 响应该请求的 URI
             *     StatusCode - 响应状态 [System.Net.HttpStatusCode枚举]
             *         HttpStatusCode.OK - HTTP 状态为 200
             *         HttpStatusCode.NotFound - HTTP 状态为 404
             *     StatusDescription - 响应状态的说明
             
*/


            HttpWebResponse response 
= state as HttpWebResponse;

            
if (response != null && response.StatusCode == HttpStatusCode.OK)
            
{
                Stream responseStream 
= response.GetResponseStream();
                
using (StreamReader sr = new StreamReader(responseStream))
                
{
                    lblMsg.Text 
= string.Format("接收的数据的内容长度:{0}\r\nHTTP 头的 ContentType 部分:{1}\r\nHTTP 方法:{2}\r\n响应该请求的 URI:{3}\r\n响应状态:{4}\r\n响应状态的说明:{5}\r\n响应的结果:{6}\r\n",
                        response.ContentLength,
                        response.ContentType,
                        response.Method,
                        response.ResponseUri,
                        response.StatusCode,
                        response.StatusDescription,
                        sr.ReadToEnd());
                }

            }

            
else
            
{
                lblMsg.Text 
= _exception;
            }

        }

    }

}


OK
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