CSVReader

using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Windows.Forms;

namespace CSV_Reader
{
    public partial class Form1 : Form
    {
        List<string> listFiles = new List<string>();

        public Form1()
        {
            InitializeComponent();
        }

        private void Button1_Click(object sender, EventArgs e)
        {
            OpenDirectory();
        }

        private void OpenDirectory()
        {
            listFiles.Clear();
            listView.Items.Clear();
            using (FolderBrowserDialog fbd = new FolderBrowserDialog()
            {
                Description = "Select your path."
            })
            {
                if (fbd.ShowDialog() == DialogResult.OK)
                {
                    txtPath.Text = fbd.SelectedPath;
                    foreach (string item in Directory.GetFiles(fbd.SelectedPath))
                    {
                        FileInfo fi = new FileInfo(item);
                        if (fi.FullName.Contains(".xlsx"))
                        {
                            imageList1.Images.Add(Icon.ExtractAssociatedIcon(item));
                            listFiles.Add(fi.FullName);
                            listView.Items.Add(fi.Name, imageList1.Images.Count - 1);
                        }
                    }
                }
            }
        }

        private void ListView_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (listView.FocusedItem != null)
            {
                ReadAllData(listFiles[listView.FocusedItem.Index]);
            }
        }

        void ReadAllData(string fileToRead)
        {
            using (var reader = new StreamReader(fileToRead))
            {
                List<string> listA = new List<string>();
                List<string> listB = new List<string>();
                while (!reader.EndOfStream)
                {
                    var line = reader.ReadLine();
                    var values = line.Split(',');

                    foreach (string item in values)
                    {
                        listA.Add(item);
                    }
                }
                DisplayData(listA);
            }
        }

        void DisplayData(IList<string> list)
        {
            foreach (string item in list)
            {
                MessageBox.Show(item);
            }
        }
    }
}