StrangeTools/PictureMover/MainForm.cs

namespace PictureMover
{
    public partial class MainForm : Form
    {
        private readonly CoverForm _form2;

        private static readonly string StateFile = Application.ExecutablePath + $".{nameof(MainForm)}.state.txt";

        public MainForm()
        {
            InitializeComponent();
            _form2 = new CoverForm(this);
        }

        private void Form_Shown(object sender, EventArgs e)
        {
            _form2.Show(this);
            Enter += Form_Enter;

            if (File.Exists(StateFile))
            {
                var state = File.ReadAllText(StateFile);
                var pars = state.Split(",")
                    .Select(p => int.TryParse(p, out var v) ? (int?)v : null)
                    .Where(p => p.HasValue)
                    .Select(p => p.Value).ToArray();
                if (pars.Length == 4)
                {
                    Left = pars[0];
                    Top = pars[1];
                    Width = pars[2];
                    Height = pars[3];
                }
            }
            FormClosed += MainForm_FormClosed;
        }

        private void MainForm_FormClosed(object? sender, FormClosedEventArgs e)
        {
            var state = $"{Left},{Top},{Width},{Height}";
            File.WriteAllText(StateFile, state);
        }

        private void Form_Enter(object? sender, EventArgs e) => _form2.Focus();
    }
}