换行符操作

 /// <summary>
        /// 替换换行符
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public string ReplaceToHTML(string str)
        {
            if (string.IsNullOrEmpty(str))
            {
                return str;
            }
            str = System.Text.RegularExpressions.Regex.Replace(str, @"\r\n", "<br/>");
            str = System.Text.RegularExpressions.Regex.Replace(str, @"\n", "<br/>");
            return str;
        }
        /// <summary>
        /// 还原换行符
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public string ReductionReplace(string str)
        {
            if (string.IsNullOrEmpty(str))
            {
                return str;
            }
            str = System.Text.RegularExpressions.Regex.Replace(str, @"<br/>", "\n");
            return str;
        }