private void UpCategory_Enter(object sender, EventArgs e)
        {
            try
            {
                Specification spec=(Specification)updateProductPage.Tag;
                ProductInfo newProduct = spec.Product ;

                using (CategorySelectWindow cateSelectWin = new CategorySelectWindow())
                {
                    DialogResult result = cateSelectWin.ShowDialog();
                    if (result == DialogResult.OK)
                    {
                        newProduct.Category = cateSelectWin.Category;
                        ApCategory.Text = newProduct.Category.CategoryName;
                    }
                }

            }
            catch (Exception ex)
            {
                Toast.Show(ex.Message);
            }
        }
        private void tbCategory_Enter(object sender, EventArgs e)
        {
            try
            {
                ProductInfo newProduct = (ProductInfo)AddProductPage.Tag;
                //AddProductPage.Tag = newProduct;
                using (CategorySelectWindow cateSelectWin = new CategorySelectWindow())
                {
                    DialogResult result = cateSelectWin.ShowDialog();
                    if (result == DialogResult.OK)
                    {
                        newProduct.Category = cateSelectWin.Category;
                        ApCategory.Text = newProduct.Category.CategoryName;
                    }
                }

            }
            catch (Exception ex)
            {
                Toast.Show(ex.Message);
            }
        }