private void button3_Click(object sender, EventArgs e)
        {
            Add_file f = new Add_file();

            f.Show();
            this.Hide();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            Add_file f = new Add_file();

            f.Show();
            this.Hide();
            //Process.Start("notepad.exe");
        }