using System;

using System.Collections.Generic;

using System.Xml;

using System.Xml.Linq;

using System.IO;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var xml = @"<?xml version=""1.0""?>

        <student_update date=""2022-04-19"" program=""CA"" checksum=""20021682"">

            <transaction>

                <program>CA</program>

                <student_no>10010823</student_no>

                <course_no>*</course_no>

                <registration_no>216</registration_no>

                <type>2</type>

                <grade>90.4</grade>

                <notes>Update Grade Test</notes>

            </transaction>

            <transaction>

                <program>CA</program>

                <student_no>10010859</student_no>

                <course_no>M-50032</course_no>

                <registration_no>*</registration_no>

                <type>1</type>

                <grade>*</grade>

                <notes>Register Course Test</notes>

            </transaction>

        </student_update>";

        XDocument xDocument = XDocument.Load(new StringReader(xml));

        XElement root = xDocument.Element("student_update");

        IEnumerable<XElement> studentnoElement = xDocument.Descendants().Where(x => x.Name == "student_no");

​

        int checksum = studentnoElement.Sum(x => Int32.Parse(x.Value));

        Console.WriteLine(checksum);

        Console.WriteLine(root.Attribute("checksum").Value.GetType());

        int rootCheckSum = Convert.ToInt32(root.Attribute("checksum").Value);

        Console.WriteLine(rootCheckSum == checksum);

        if (!rootCheckSum.Equals(checksum))

        {

          //throw new Exception(String.Format("Incorrect checksum total " + "for file {0}\n", inputFileName));

            throw new Exception(String.Format("Incorrect checksum total " + "for file \n"));

        }

    }

}