C#獲得字元串中開始和結束字元中間的字元串

/// <summary>
        /// 獲得字元串中開始和結束字元中間的值
        /// </summary>
        /// <param name="str"></param>
        /// <param name="s">開始</param>
        /// <param name="e">結束</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;
        }