private void rentACarToolStripMenuItem_Click(object sender, EventArgs e)
        {
            CustomerRent cr = new CustomerRent();

            cr.Dock = DockStyle.Fill;
            this.crpanel.Controls.Clear();
            this.crpanel.Controls.Add(cr);
            cr.Show();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            CustomerRent cr = new CustomerRent();

            cr.Show();
        }