C#获得字符串中开始和结束字符中间的字符串

/// <summary>
        /// 获得字符串中开始和结束字符中间的值
        /// </summary>
        /// <param name="str"></param>
        /// <param name="s">开始</param>
        /// <param name="e">结束</param>
        /// <returns></returns> 
        private string GetRegexValue(string str, string s, string e)
        {
            var regVal = "(?<=" + s + ").*?(?=\\" + e + ")";
            Regex rg = new Regex(regVal, RegexOptions.Singleline);
            return rg.Match(str).Value;
        }