/**//// <summary>
        /// 删除字符串尾部的回车/换行/空格
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static string RTrim(string str)
        {
            for (int i = str.Length; i >= 0; i--)
            {
                if (str[i].Equals(" ") || str[i].Equals("\r") || str[i].Equals("\n"))
                {
                    str.Remove(i, 1);
                }
            }
            return str;
        }

        /**//// <summary>
        /// 返回文件是否存在
        /// </summary>
        /// <param name="filename">文件名</param>
        /// <returns>是否存在</returns>
        public static bool FileExists(string filename)
        {
            return System.IO.File.Exists(filename);
        }

        /**//// <summary>
        /// 以指定的ContentType输出指定文件文件
        /// </summary>
        /// <param name="filepath">文件路径</param>
        /// <param name="filename">输出的文件名</param>
        /// <param name="filetype">将文件输出时设置的ContentType</param>
        public static void ResponseFile(string filepath, string  filename, string filetype)
        {
            Stream iStream = null;

            // 缓冲区为10k
            byte[] buffer = new Byte[10000];

            // 文件长度
            int length;

            // 需要读的数据长度
            long dataToRead;

            try
            {
                // 打开文件
                iStream = new FileStream(filepath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);


                // 需要读的数据长度
                dataToRead = iStream.Length;

                HttpContext.Current.Response.ContentType = filetype;
                HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + Utils.UrlEncode(filename.Trim()).Replace("+", " "));

                while (dataToRead > 0)
                {
                    // 检查客户端是否还处于连接状态
                    if (HttpContext.Current.Response.IsClientConnected)
                    {
                        length = iStream.Read(buffer, 0, 10000);
                        HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);
                        HttpContext.Current.Response.Flush();
                        buffer = new Byte[10000];
                        dataToRead = dataToRead - length;
                    }
                    else
                    {
                        // 如果不再连接则跳出死循环
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                HttpContext.Current.Response.Write("Error : " + ex.Message);
            }
            finally
            {
                if (iStream != null)
                {
                    // 关闭文件
                    iStream.Close();
                }
            }
            HttpContext.Current.Response.End();
        }

        /**//// <summary>
        /// 判断文件名是否为浏览器可以直接显示的图片文件名
        /// </summary>
        /// <param name="filename">文件名</param>
        /// <returns>是否可以直接显示</returns>
        public static bool IsImgFilename(string filename)
        {
            filename = filename.Trim();
            if (filename.EndsWith(".") || filename.IndexOf(".") == -1)
            {
                return false;
            }
            string extname = filename.Substring(filename.LastIndexOf(".") + 1).ToLower();
            return (extname == "jpg" || extname == "jpeg" || extname == "png" || extname == "bmp" || extname == "gif");
        }

        /**//// <summary>
        /// MD5函数
        /// </summary>
        /// <param name="str">原始字符串</param>
        /// <returns>MD5结果</returns>
        public static string MD5(string str)
        {
            byte[] b = Encoding.Default.GetBytes(str);
            b = new MD5CryptoServiceProvider().ComputeHash(b);
            string ret = "";
            for(int i = 0; i < b.Length; i++)
                ret += b[i].ToString("x").PadLeft(2,'0');
            return ret;
        }

        /**//// <summary>
        /// SHA256函数
        /// </summary>
        /// /// <param name="str">原始字符串</param>
        /// <returns>SHA256结果</returns>
        public static string SHA256(string str)
        {
            byte[] SHA256Data = Encoding.UTF8.GetBytes(str);
            SHA256Managed Sha256 = new SHA256Managed();
            byte[] Result = Sha256.ComputeHash(SHA256Data);
            return Convert.ToBase64String(Result);  //返回长度为44字节的字符串
        }

        /**//// <summary>
        /// 检测是否符合email格式
        /// </summary>
        /// <param name="strEmail">要判断的email字符串</param>
        /// <returns>判断结果</returns>
        public static bool IsValidEmail(string strEmail)
        {
            return Regex.IsMatch(strEmail, @"^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$");
        }

        public static bool IsValidDoEmail(string strEmail)
        {
            return Regex.IsMatch(strEmail, @"^@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$");
        }

        /**//// <summary>
        /// 检测是否是正确的Url
        /// </summary>
        /// <param name="strUrl">要验证的Url</param>
        /// <returns>判断结果</returns>
        public static bool IsURL(string strUrl)
        {
            return Regex.IsMatch(strUrl, @"^(http|https)\://([a-zA-Z0-9\.\-]+(\:[a-zA-Z0-9\.&%\$\-]+)*@)*((25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9])\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[0-9])|localhost|([a-zA-Z0-9\-]+\.)*[a-zA-Z0-9\-]+\.(com|edu|gov|int|mil|net|org|biz|arpa|info|name|pro|aero|coop|museum|[a-zA-Z]{1,10}))(\:[0-9]+)*(/($|[a-zA-Z0-9\.\,\?\'\\\+&%\$#\=~_\-]+))*$");
        }

        public static string GetEmailHostName(string strEmail)
        {
            if (strEmail.IndexOf("@") < 0)
            {
                return "";
            }
            return strEmail.Substring(strEmail.LastIndexOf("@")).ToLower();
        }

        /**//// <summary>
        /// 检测是否有Sql危险字符
        /// </summary>
        /// <param name="str">要判断字符串</param>
        /// <returns>判断结果</returns>
        public static bool IsSafeSqlString(string str)
        {

            return !Regex.IsMatch(str, @"[-|;|,|\/|\(|\)|\[|\]|\}|\{|%|@|\*|!|\']"); 
        }

        /**//// <summary>
        /// 替换回车换行符为html换行符
        /// </summary>
        public static string StrFormat(string str)
        {
            string str2;

            if (str == null)
            {
                str2 = "";
            }
            else
            {
                str = str.Replace("\r\n", "<br />");
                str = str.Replace("\n", "<br />");
                str2 = str;
            }
            return str2;
        }

        /**//// <summary>
        /// 转换为简体中文
        /// </summary>
        public static string ToSChinese(string str)
        {
            return Strings.StrConv(str, VbStrConv.SimplifiedChinese, 0) ;
        }

        /**//// <summary>
        /// 转换为繁体中文
        /// </summary>
        public static string ToTChinese(string str)
        {
            return Strings.StrConv(str, VbStrConv.TraditionalChinese, 0);
        }

        /**//// <summary>
        /// 返回 HTML 字符串的编码结果
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns>编码结果</returns>
        public static string HtmlEncode(string str)
        {
            return HttpUtility.HtmlEncode(str);
        }

        /**//// <summary>
        /// 返回 HTML 字符串的解码结果
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns>解码结果</returns>
        public static string HtmlDecode(string str)
        {
            return HttpUtility.HtmlDecode(str);
        }

        /**//// <summary>
        /// 返回 URL 字符串的编码结果
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns>编码结果</returns>
        public static string UrlEncode(string str)
        {
            return HttpUtility.UrlEncode(str);
        }

        /**//// <summary>
        /// 返回 URL 字符串的编码结果
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns>解码结果</returns>
        public static string UrlDecode(string str)
        {
            return HttpUtility.UrlDecode(str);
        }

        /**//// <summary>
        /// 写cookie值
        /// </summary>
        /// <param name="strName">名称</param>
        /// <param name="strValue">值</param>
        /// <param name="strValue">过期时间(分钟)</param>
        public static void WriteCookie(string strName, string strValue, int expires)
        {
            HttpCookie cookie = HttpContext.Current.Request.Cookies[strName];
            if (cookie == null)
            {
                cookie = new HttpCookie(strName);
            }
            cookie.Value = strValue;
            cookie.Expires = DateTime.Now.AddMinutes(expires);
            HttpContext.Current.Response.AppendCookie(cookie);

        }

        /**//// <summary>
        /// 读cookie值
        /// </summary>
        /// <param name="strName">名称</param>
        /// <returns>cookie值</returns>
        public static string GetCookie(string strName)
        {
            if (HttpContext.Current.Request.Cookies != null && HttpContext.Current.Request.Cookies[strName] != null)
            {
                return HttpContext.Current.Request.Cookies[strName].Value.ToString();
            }

            return "";
        }

        /**//// <summary>
        /// 过滤HTML中的不安全标签
        /// </summary>
        /// <param name="content"></param>
        /// <returns></returns>
        public static string RemoveUnsafeHtml(string content)
        {
            content = Regex.Replace(content, @"(\<|\s+)o([a-z]+\s?=)", "$1$2", RegexOptions.IgnoreCase);
            content = Regex.Replace(content, @"(script|frame|form|meta|behavior|style)([\s|:|>])+", "$1.$2", RegexOptions.IgnoreCase);
            return content;
        }