private void button3_Click(object sender, EventArgs e)
        {
            try
            {
                ///delete product
                string    proName    = comboBox1.Text;
                Inventory dltProduct = db.Inventories.SingleOrDefault(x => x.product_name == proName);
                db.Inventories.DeleteOnSubmit(dltProduct);
                db.SubmitChanges();
                MessageBox.Show("Product Deleted");

                //opening this window by refershing again
                Hide();
                InventoryClass newObj = new InventoryClass();
                newObj.whoLoggedIn = this.whoLoggedIn;
                newObj.Show();
            }
            catch { MessageBox.Show("No Product Selected"); }
        }