protected void btnDelete_Click(object sender, EventArgs e)
{
Button btnXoa = sender as Button;
GridViewRow grvr = btnXoa.NamingContainer as GridViewRow;
int proid = int.Parse(GridView1.DataKeys[grvr.RowIndex].Value.ToString());
bus.DeleteProduct(proid);
string alert = "Xóa thành công";
Response.Redirect("~/Page/Admin/Product/Product.aspx?alert=" + alert);
}