奇怪的400错误！WebRequest访问Url地址报400错误，用IE访问则正常

Question

最近用C#写代码，遇见一个奇怪的问题。用WebRequest对象访问一个Url地址，被报400错误。但是同样的Url在浏览器（如IE）中访问时并没有报错，很正常。把握郁闷坏啦。有碰到这类问题的朋友吗？指点一下。代码如下：
        static void Main(string[] args)
        {
            Console.WriteLine("测试\n=============================");            string url = @"http://bbs.360safe.com/forumdisplay.php?fid=22&page=1";            try
            {
                WebRequest request = WebRequest.Create(url);
                Console.WriteLine("Method: {0}", request.Method);
                Console.WriteLine("ContentType  : {0}", request.ContentType);
                WebResponse response = request.GetResponse();
                Stream stream = response.GetResponseStream();
                StreamReader sr = new StreamReader(stream, Encoding.Default);
                string html = sr.ReadToEnd();
                response.Close();
                Console.WriteLine("[WebRequest下载：" + html.Length.ToString() + " 字符] ");            }
            catch (WebException e)
            {
                Console.WriteLine("[WebRequest下载出错0：" + e.Message + "] ");
            }
            catch (Exception e)
            {
                Console.WriteLine("[WebRequest下载出错0：" + e.Message + "] ");
            }            Console.ReadLine();
        }

Answer 1

可能要传cookie用HttpWebRequest 试试
  
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Answer 2

代理问题  string url = @"http://bbs.360safe.com/forumdisplay.php?fid=22&page=1";
            string strhtml = Internet.GetHtml(url);using System;
using System.Net;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
public static class Internet
{
   private static HttpWebRequest request;
  private static  HttpWebResponse response;
   private static  StreamReader reader;
    private static string strResults;
    private static Encoding encoding;
    static Internet()
    {
        strResults = string.Empty;
    }
    public static string GetHtml(string strLink)
    {
       
        try
        {            request = (HttpWebRequest)WebRequest.Create(strLink);
            switch ((DateTime.Now.Second % 2))
            {
                case 0:
                    request.UserAgent = "Mozilla/5.0 (compatible; MSIE 7.0; Windows NT 5.1; SV1;.NET CLR 2.0.50727)";
                    break;                default:
                    request.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.1) Web-Sniffer/1.0.24";
                    break;
            }
            response = (HttpWebResponse)request.GetResponse();
         
            if (response.CharacterSet != null && response.CharacterSet.ToLower() == "utf-8")
            {
                encoding = Encoding.UTF8;
            }
            else
            {
                encoding = Encoding.GetEncoding(936);
            }
            reader = new StreamReader(response.GetResponseStream(),encoding);
            strResults = Regex.Replace(reader.ReadToEnd(), @"[\r\n]", " ");
            if (strLink != response.ResponseUri.ToString())
            {
                strResults = "|RedirectWeb|" + strResults;
            }
            return strResults;
        }
        catch
        {
            return string.Empty;
        }
        finally
        {
            request.Abort();
            if (response != null)
            {
                response.Close();
            }
            if (reader != null)
            {
                reader.Close();
                reader.Dispose();
            }
        }    }
}

Answer 3

问题解决了。根据hackztx方法测试，确实是用户代理问题。多谢！