How to check whether user defined date format matches with element value’s date format at XPath?

public bool match_elementval_with_given_date_format(string user_given_xpath, string user_defined_xml, string expected_date_format)
        {
            bool result = false;            
            XmlDocument user_defined_xml_document = new XmlDocument();
            user_defined_xml_document.Load(user_defined_xml);
            XmlNodeList myNodeList = user_defined_xml_document.SelectNodes(user_given_xpath);
            foreach (XmlNode myNode in myNodeList)
            {
                bool get_result = date_format_validate (myNode.InnerText.Trim() , expected_date_format);
               if (get_result == true)
                {
                    result = true;                       
                    return result;
                }
                else
                {
                    result = false;
                    
                }
            }
             
            return result;
        }

        public bool date_format_validate(string date, string date_format)
        {
            try
            {
                DateTime.ParseExact(date, date_format, DateTimeFormatInfo.InvariantInfo);
            }
            catch
            {
                return false;
            }
            return true;
        }