我想用C#实现从网站上下载文件的功能，我只知道该网站的链接，而且链接是有规律的变化的，不知道用C#如何实现呐？？？
期待……多谢了

  public Uri fixurl(string url, Uri baseurl)
        {
            if (url.IndexOf("javascript:") >= 0) { return null; }
            Uri u = null;
            Uri.TryCreate(baseurl, url, out u);
            return u;
        }

httpwebrequest获取页面内容
正则获取URL
再使用webclient等下载文件
MatchCollection mc= Regex.Matches(str, @" <a[^> ]*href=([ ' " "]?)(? <url> [^ ' " "> \s]*)\1?[^> ]*> (? <text> [^ <]*) </a> ", RegexOptions.IgnoreCase);   
foreach (Match m in mc)   
{   
  Response.Write(m.Groups[ "url "].Value);   
  Response.Write(m.Groups[ "text "].Value);   
}   

/// <summary>
        /// 获取网页源代码
        /// </summary>
        /// <param name="strLink"></param>
        /// <returns></returns>
        public static string GetHtml(string strLink)
        {
            Encoding encoding;
            StreamReader reader = null;
            string strResults;
            HttpWebRequest request = null;
            HttpWebResponse response = null;
            try
            {
                if (strLink.IndexOf(@"http://") >= 0)
                {
                    request = (HttpWebRequest)WebRequest.Create(strLink);
                   
                    
                }
                else
                {
                    request = (HttpWebRequest)WebRequest.Create(string.Format(@"http://{0}",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]", " ", RegexOptions.IgnoreCase);
                if (strLink != response.ResponseUri.ToString())
                {
                    strResults = "|RedirectWeb|" + strResults;
                }
                return strResults;
            }
            catch
            {
                return string.Empty;
            }
            finally
            {
                if (request != null)
                {
                    request.Abort();
                }
                if (response != null)
                {
                    response.Close();
                }
                if (reader != null)
                {
                    reader.Close();
                    reader.Dispose();
                }
            }

        }

看看先。。谢谢了