namespace Assignment_2_module_marks
{
    public partial class Form1 : Form
    {
        public static List<string> studentInfo = new List<string>(); // Declaring a list structure and making it public so that it can be accessed across forms

        public Form1()
        {
            InitializeComponent();
            StartPosition = FormStartPosition.CenterScreen;
        }

        Stats myStats = new Stats(); // Calls the Stats class

        private void Form1_Load(object sender, EventArgs e)
        {
            string lines, studentNumber, studentMark;  // Declaring string variables

            StreamReader inputFile = File.OpenText("COM122.csv"); // Declaring a streamReader called inputfile and setting it to the data file

            while (!inputFile.EndOfStream)  // While not at the end of the file execute the while loop
            {
                lines = inputFile.ReadLine(); // Read all the lines in the file and store it to the lines variable
                studentInfo = lines.Split(',').ToList();  // Split all the lines after the ',' and coverts it to a list
                studentNumber = studentInfo[0];  // Store the value of the first index of studentInfo to the variable studentNumber
                studentMark = studentInfo[1];  // Store the value of the second index of studentInfo to the variable studentMark
                lstMarks.Items.Add(studentNumber + " : " + studentMark);  // Add the studentNumber and studentMark together and store it in the listbox
            }
            inputFile.Close(); // closes the file
        }

        private void btnAddMark_Click(object sender, EventArgs e)
        {
            addRecord myAddRecordForm = new addRecord(); // Opens a form called addRecord
            if (myAddRecordForm.ShowDialog() == DialogResult.OK) // If statement will run if the dialogResult is set to OK in the addRecord form
            {
                studentInfo.Add(myAddRecordForm.StudentID); // Adds the student ID to the studentInfo List
                studentInfo.Add(myAddRecordForm.Mark); // Adds the Mark to the studentInfo List
                lstMarks.Items.Add(myAddRecordForm.StudentID + " : " + myAddRecordForm.Mark); // Adds the StudentID and Mark to the listbox
            }
        }

        private void btnEditMark_Click(object sender, EventArgs e)
        {
            editMark myEditRecordForm = new editMark(); // Opens a form called editMark
            this.Hide(); // Hides the previous form
            myEditRecordForm.ShowDialog(); // Shows the form
        }

        private void btnDeleteMark_Click(object sender, EventArgs e)
        {
            deleteRecord myDeleteRecordForm = new deleteRecord(); // Opens a form called deleteRecord
            this.Hide(); // Hides the previous form
            myDeleteRecordForm.ShowDialog(); // Shows the form
        }

        private void btnMax_Click(object sender, EventArgs e)
        {


        }

        private void btnMin_Click(object sender, EventArgs e)
        {

        }

        private void btnAverage_Click(object sender, EventArgs e)
        {
            double average;

            average = myStats.AverageMark(studentInfo);

            lblOutput.Text = average.ToString();
        }

        private void btnSaveToFile_Click(object sender, EventArgs e)
        {
            StreamWriter outputFile = File.AppendText("MODULEMARKS.csv");  // Declaring a streamwriter and naming it outputfile and sets the output location

            outputFile.WriteLine(); //Writes the average to the file

            outputFile.Close(); // Closes the outputfile

            MessageBox.Show("Student Information inserted successfully"); // Displays a message to the user
        }

        private void btnExit_Click(object sender, EventArgs e)
        {
            this.Close(); // Closes the program
        }
    }
}




Class :

namespace Assignment_2_module_marks
{
    class Stats
    {
        //public int maxMarks()
        //{
        //    int Max;

        //    //return Max;
        //}
        //public int minMarks()
        //{
        //    int Min;

        //    return Min;
        //}
        public double AverageMark(List<string> studentInfo)
        {
            int total = 0;

            foreach(int x in studentInfo[1])
            {
                total += x;
                MessageBox.Show(x.ToString());  // outputs 55 and 57 for some reason
            }
            return total / studentInfo.Count;
        }
    }
}