Quick script to read file contents to ArrayList and search the ArrayList for matching contents

Form1.cs

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private static readonly string FilePath = Path.Combine(Application.StartupPath, "txt1.txt");

        private static readonly string ErrorLog = FilePath.Replace(Path.GetFileName(FilePath), "errorlog.log");
        private static readonly ArrayList ArrList = new ArrayList();

        private static ArrayList ReadDataToArrayList(string address)
        {
            try
            {
                string data = File.ReadAllText(address);
                if (data.Length > 0 && !ArrList.Contains(data))
                    ArrList.Add(data);
            }
            catch (Exception ex)
            {
                /* Handle error or write error log */
                File.AppendAllText(ErrorLog, string.Concat(Environment.NewLine, $"Exception Message : ",
                    $"{string.Concat(Environment.NewLine, ex.Message, Environment.NewLine, "Exception Stack : ", Environment.NewLine, ex.StackTrace)} "));
                return ArrList;
            }
            return ArrList;
        }

        private void Button1_Click(object sender, EventArgs e)
        {
            bool condition = File.Exists(FilePath);
            if (condition) { label1.Text = $"File Exists : {condition}"; ReadDataToArrayList(FilePath); }
            else { label1.Text = $"File Exist : {condition}"; }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (ArrList.Count > 0)
                label2.Text = ArrList[0].ToString();
            else label2.Text = "There was nothing to read.";
            ArrList.Clear();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            for (int i = 0; i < ArrList.Count; i++)
            {
                if (ArrList[i].ToString().Contains(textBox1.Text))
                    label2.Text = ArrList[i].ToString();
                else label2.Text = "No matches found.";
            }
        }
    }