protected void btn_Add_Click(object sender, EventArgs e)
{
//some code
if (condition)
{
//pop up This product already exist? Do need to add it again?
}
//add it DataTable and bind grid view
}
Adding some products along with some other details to Datatable and binding it to Grid view. If the product is already exist need to ask Do you want to add it again. If he says yes I need to add it.