private void button2_Click(object sender, EventArgs e)
        {
            UserEnter us = new UserEnter();

            this.Hide();
            us.Show();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            UserEnter userenter = new UserEnter();

            this.Hide();
            userenter.Show();

            //  axAcroPDF1.LoadFile("C:\\Users\\Döndü Demir\\Desktop\\kitap.pdf");
        }