string str = @"test_{@ReportDate:yyyyMMdd}\{@ReportDate:yyyy}\{@ReportDate:MM}\{@ReportDate:dd}\ss.xls";
            Regex regex = new Regex(@"\{@ReportDate:(?<p>[a-zA-Z]*)\}");
            DateTime time = DateTime.Now;string r = regex.Replace(str, match =>
            {
                var p = match.Groups["p"].Value;
                var t = time.ToString(p);
                return t;
            });