原文地址:http://www.cameronalbert.com/post/2008/03/HttpWebRequest-Helper-for-Silverlight-2.aspx
using System;
using System.Collections.Generic;
using System.IO;
using System.Windows;
using System.Windows.Browser;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Net;
namespace Lionsguard
{
public class HttpHelper
{
private HttpWebRequest Request { get; set; }
public Dictionary<string, string> PostValues { get; private set; }
public event HttpResponseCompleteEventHandler ResponseComplete;
private void OnResponseComplete(HttpResponseCompleteEventArgs e)
{
if (this.ResponseComplete != null)
{
this.ResponseComplete(e);
}
}
public HttpHelper(Uri requestUri, string method, params KeyValuePair<string, string>[] postValues)
{
this.Request = (HttpWebRequest)WebRequest.Create(requestUri);
this.Request.ContentType = "application/x-www-form-urlencoded";
this.Request.Method = method;
this.PostValues = new Dictionary<string, string>();
if (postValues != null && postValues.Length > 0)
{
foreach (var item in postValues)
{
this.PostValues.Add(item.Key, item.Value);
}
}
}
public void Execute()
{
this.Request.BeginGetRequestStream(new AsyncCallback(HttpHelper.BeginRequest), this);
}
private static void BeginRequest(IAsyncResult ar)
{
HttpHelper helper = ar.AsyncState as HttpHelper;
if (helper != null)
{
if (helper.PostValues.Count > 0)
{
using (StreamWriter writer = new StreamWriter(helper.Request.EndGetRequestStream(ar)))
{
foreach (var item in helper.PostValues)
{
writer.Write("{0}={1}&", item.Key, HttpUtility.UrlEncode(item.Value));
}
}
}
helper.Request.BeginGetResponse(new AsyncCallback(HttpHelper.BeginResponse), helper);
}
}
private static void BeginResponse(IAsyncResult ar)
{
HttpHelper helper = ar.AsyncState as HttpHelper;
if (helper != null)
{
HttpWebResponse response = (HttpWebResponse)helper.Request.EndGetResponse(ar);
if (response != null)
{
Stream stream = response.GetResponseStream();
if (stream != null)
{
using (StreamReader reader = new StreamReader(stream))
{
helper.OnResponseComplete(new HttpResponseCompleteEventArgs(reader.ReadToEnd()));
}
}
}
}
}
}
public delegate void HttpResponseCompleteEventHandler(HttpResponseCompleteEventArgs e);
public class HttpResponseCompleteEventArgs : EventArgs
{
public string Response { get; set; }
public HttpResponseCompleteEventArgs(string response)
{
this.Response = response;
}
}
}
使用方法
private void ProcessCommand(short cmd, string msg)
{
App app = App.Current as App;
HttpHelper helper = new HttpHelper(app.ServerUri, "POST",
new KeyValuePair<string, string>("authKey", app.AuthKey),
new KeyValuePair<string, string>("cmd", cmd.ToString()),
new KeyValuePair<string, string>("msg", msg));
helper.ResponseComplete += new HttpResponseCompleteEventHandler(this.CommandComplete);
helper.Execute();
}
private void CommandComplete(HttpResponseCompleteEventArgs e)
{
txtAlert.Text = e.Response;
}
如果您使用的是VBScript的话，工具类代码如下：
Public Class HttpHelper
Private Property Request() As HttpWebRequest
Get
Return _Request
End Get
Set(ByVal value As HttpWebRequest)
_Request = value
End Set
End Property
Private _Request As HttpWebRequest
Public Property PostValues() As Dictionary(Of String, String)
Get
Return _PostValues
End Get
Private Set(ByVal value As Dictionary(Of String, String))
_PostValues = value
End Set
End Property
Private _PostValues As Dictionary(Of String, String)
Public Event ResponseComplete As HttpResponseCompleteEventHandler
Private Sub OnResponseComplete(ByVal e As HttpResponseCompleteEventArgs)
RaiseEvent ResponseComplete(e)
End Sub
Public Sub New(ByVal requestUri As Uri, ByVal method As String, ByVal ParamArray postValues As KeyValuePair(Of String, String)())
Me.Request = DirectCast(WebRequest.Create(requestUri), HttpWebRequest)
Me.Request.ContentType = "application/x-www-form-urlencoded"
Me.Request.Method = method
Me.PostValues = New Dictionary(Of String, String)()
For Each item In postValues
Me.PostValues.Add(item.Key, item.Value)
Next
End Sub
Public Sub Execute()
Me.Request.BeginGetRequestStream(New AsyncCallback(AddressOf HttpHelper.BeginRequest), Me)
End Sub
Private Shared Sub BeginRequest(ByVal ar As IAsyncResult)
Dim helper As HttpHelper = TryCast(ar.AsyncState, HttpHelper)
If helper IsNot Nothing Then
Using writer As New StreamWriter(helper.Request.EndGetRequestStream(ar))
For Each item In helper.PostValues
writer.Write("{0}={1}&", item.Key, HttpUtility.UrlEncode(item.Value))
Next
End Using
helper.Request.BeginGetResponse(New AsyncCallback(AddressOf HttpHelper.BeginResponse), helper)
End If
End Sub
Private Shared Sub BeginResponse(ByVal ar As IAsyncResult)
Dim helper As HttpHelper = TryCast(ar.AsyncState, HttpHelper)
If helper IsNot Nothing Then
Dim response As HttpWebResponse = DirectCast(helper.Request.EndGetResponse(ar), HttpWebResponse)
If response IsNot Nothing Then
Dim stream As Stream = response.GetResponseStream()
If stream IsNot Nothing Then
Using reader As New StreamReader(stream)
helper.OnResponseComplete(New HttpResponseCompleteEventArgs(reader.ReadToEnd()))
End Using
End If
End If
End If
End Sub
End Class
Public Delegate Sub HttpResponseCompleteEventHandler(ByVal e As HttpResponseCompleteEventArgs)
Public Class HttpResponseCompleteEventArgs
Inherits EventArgs
Public Property Response() As String
Get
Return _Response
End Get
Set(ByVal value As String)
_Response = value
End Set
End Property
Private _Response As String
Public Sub New(ByVal response As String)
Me.Response = response
End Sub
End Class
在做自动更新程序时想省点事，直接使用HttpWebRequest和HttpWebResponse从服务器上下载更新的文件。 使用时注意Close响应流:
使用HttpWebRequest.GetResponse()取得HttpWebResponse接口后，必须要记得调用HttpWebResponse.close关闭流。
如果使用HttpWebResponse.GetResponseStream()取得响应流的话，那么使用此Stream的Close方法来关闭也是一样。
如果是使用StreamReader.ReadToEnd()从响应流中读取文本，则在读取完内容后会自动关闭流。
MSDN中这样描述HttpWebResponse.close方法：
Close 方法关闭响应流并释放到资源的连接以供其他请求重用。
您必须调用 Stream.Close 或 HttpWebResponse.Close 方法来关闭流并释放连接以供重用。不必同时调用 Stream.Close 和 HttpWebResponse.Close，但这样做不会导致错误。关闭该流失败会导致应用程序用尽连接。
连接限制好像是最大2个，不知是IIS的限制还是本地HttpWebRequest的限制。