private void newProduct_Click(object sender, EventArgs e)
        {
            sidePanel.Height = newProduct.Height;
            sidePanel.Top    = newProduct.Top;
            addProduct tab = new addProduct();

            MainControlClass.showControl(tab, content);
        }
        private void back_Click(object sender, EventArgs e)
        {
            addProduct d1 = new addProduct();

            MainControlClass.showControl(d1, this);
        }