c# 过滤特殊字符

 /// <summary>
        /// 过滤特殊字符
        /// </summary>
        /// <param name="Input"></param>
        /// <returns></returns>
        public static string Htmls(string Input)
        {
            if (Input != string.Empty && Input != null)
            {
                string ihtml = Input.ToLower();
                ihtml = ihtml.Replace("<script", "&lt;script");
                ihtml = ihtml.Replace("script>", "script&gt;");
                ihtml = ihtml.Replace("<%", "&lt;%");
                ihtml = ihtml.Replace("%>", "%&gt;");
                ihtml = ihtml.Replace("<$", "&lt;$");
                ihtml = ihtml.Replace("$>", "$&gt;");
                return ihtml;
            }
            else
            {
                return string.Empty;
            }
        }

        /// <summary>
        /// 不区分大小写
        /// </summary>
        /// <param name="Input"></param>
        /// <returns></returns>
        public static string Htmlsr(string Input)
        {
            if (Input != string.Empty && Input != null)
            {
                string ihtml = Input;
                ihtml = ihtml.Replace("<script", "&lt;script");
                ihtml = ihtml.Replace("script>", "script&gt;");
                ihtml = ihtml.Replace("<%", "&lt;%");
                ihtml = ihtml.Replace("%>", "%&gt;");
                ihtml = ihtml.Replace("<$", "&lt;$");
                ihtml = ihtml.Replace("$>", "$&gt;");
                return ihtml;
            }
            else
            {
                return string.Empty;
            }
        }