How to check whether element value at any XPath is alphanumeric or not.

You have to create a class library and place following code in to it.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Text.RegularExpressions;

namespace yournamespace.subfoldername
{
    class DoCheckAlphanueric
    {
        public bool chkelementvalueaphanumeric(string yourXMLfile, string yourXPathValue)
        {
            bool result = false;
            XmlDocument doc = new XmlDocument();
            doc.Load(yourXMLfile);
            XmlNodeList myNodeList = doc.SelectNodes(yourXPathValue);
            foreach (XmlNode myNode in myNodeList)
            {
                Regex pattern = new Regex("^[a-zA-Z0-9]*$");
                string[] result = myNode.InnerText.Trim().Split(new string[] { "\n", "\r\n" }, StringSplitOptions.RemoveEmptyEntries);
                foreach (string s in result)
                {
                    if (pattern.IsMatch(s))
                    {
                        result = true;
                        return result;
                    }
                    else
                    {
                        result = false;
                    }
                }
            }
            return result; 
        }

    }
}