C# Http请求（GET/HTTP/HTTPS）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;
using System.DirectoryServices.Protocols;
using System.ServiceModel.Security;
using System.Net;
using System.IO;
using System.IO.Compression;
using System.Text.RegularExpressions;  

namespace BaiduCang
{
   /// <summary>
   /// 有关HTTP请求的辅助类
   /// </summary>
   public class HttpWebResponseUtility
   {
       private static readonly string DefaultUserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";
       /// <summary>
       /// 创建GET方式的HTTP请求
       /// </summary>
       /// <param name="url">请求的URL</param>
       /// <param name="timeout">请求的超时时间</param>
       /// <param name="userAgent">请求的客户端浏览器信息，可以为空</param>
       /// <param name="cookies">随同HTTP请求发送的Cookie信息，如果不需要身份验证可以为空</param>
       /// <returns></returns>
       public static HttpWebResponse CreateGetHttpResponse(string url,int? timeout, string userAgent,CookieCollection cookies)
       {
           if (string.IsNullOrEmpty(url))
           {
               throw new ArgumentNullException("url");
           }
           HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
           request.Method = "GET";
           request.UserAgent = DefaultUserAgent;
           if (!string.IsNullOrEmpty(userAgent))
           {
               request.UserAgent = userAgent;
           }
           if (timeout.HasValue)
           {
               request.Timeout = timeout.Value;
           }
           if (cookies != null)
           {
               request.CookieContainer = new CookieContainer();
               request.CookieContainer.Add(cookies);
           }
           return request.GetResponse() as HttpWebResponse;
       }
       /// <summary>
       /// 创建POST方式的HTTP请求
       /// </summary>
       /// <param name="url">请求的URL</param>
       /// <param name="parameters">随同请求POST的参数名称及参数值字典</param>
       /// <param name="timeout">请求的超时时间</param>
       /// <param name="userAgent">请求的客户端浏览器信息，可以为空</param>
       /// <param name="requestEncoding">发送HTTP请求时所用的编码</param>
       /// <param name="cookies">随同HTTP请求发送的Cookie信息，如果不需要身份验证可以为空</param>
       /// <returns></returns>
       public static HttpWebResponse CreatePostHttpResponse(string url,IDictionary<string,string> parameters,int? timeout, string userAgent,Encoding requestEncoding,CookieCollection cookies)
       {
           if (string.IsNullOrEmpty(url))
           {
               throw new ArgumentNullException("url");
           }
           if(requestEncoding==null)
           {
               throw new ArgumentNullException("requestEncoding");
           }
           HttpWebRequest request=null;
           //如果是发送HTTPS请求
           if(url.StartsWith("https",StringComparison.OrdinalIgnoreCase))
           {
               ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
               request = WebRequest.Create(url) as HttpWebRequest;
               request.ProtocolVersion=HttpVersion.Version10;
           }
           else
           {
               request = WebRequest.Create(url) as HttpWebRequest;
           }
           request.Method = "POST";
           request.ContentType = "application/x-www-form-urlencoded";  

           if (!string.IsNullOrEmpty(userAgent))
           {
               request.UserAgent = userAgent;
           }
           else
           {
               request.UserAgent = DefaultUserAgent;
           }  

           if (timeout.HasValue)
           {
               request.Timeout = timeout.Value;
           }
           if (cookies != null)
           {
               request.CookieContainer = new CookieContainer();
               request.CookieContainer.Add(cookies);
           }
           //如果需要POST数据
           if(!(parameters==null||parameters.Count==))
           {
               StringBuilder buffer = new StringBuilder();
               int i = ;
               foreach (string key in parameters.Keys)
               {
                   if (i > )
                   {
                       buffer.AppendFormat("&{0}={1}", key, parameters[key]);
                   }
                   else
                   {
                       buffer.AppendFormat("{0}={1}", key, parameters[key]);
                   }
                   i++;
               }
               byte[] data = requestEncoding.GetBytes(buffer.ToString());
               using (Stream stream = request.GetRequestStream())
               {
                   stream.Write(data, , data.Length);
               }
           }
           return request.GetResponse() as HttpWebResponse;
       }  

       private static bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
       {
           return true; //总是接受
       }
   }
}