ASP.NET网站生成静态页面，写入HTML文件有成功，有报错。

采集方法：     
   public static string GetFileContent(string url, string encoding)
        {
            try
            {
                WebClient web = new WebClient();
                web.Credentials = CredentialCache.DefaultCredentials;
                byte[] buffer = web.DownloadData(url);
                web.Dispose();
                if (object.Equals(web.ResponseHeaders, null))
                    return "";

                return Encoding.GetEncoding(encoding).GetString(buffer); ;
            }
            catch
            {

            }
            return "";
        }
生成静态HTML文件：
string _content = GetFileContent("http://127.0.0.1/default.aspx", "utf-8");//抓取内容   地址如http://127.0.0.1/news.aspx?id=1           
                    if (_content.Length > 50)
                    {
                        savepath = "d:website"; //如：d:websitenews
                        if (Directory.Exists(savepath.Remove(savepath.LastIndexOf('/') + 1)) == false)
                            Directory.CreateDirectory(savepath.Remove(savepath.LastIndexOf('/') + 1));
                        File.WriteAllText(savepath, _content, Encoding.UTF8);//页面存储
                    }

问题：File.WriteAllText(savepath, _content, Encoding.UTF8) 生成静态保存为html文件的时候，有的生成静态并保存成功了，有的不可以。而且根目录下的文件始终生成不了静态（如:http://127.0.0.1 /news.aspx要生成为d:websitenews.html）。求帮助。