partial void Purchase_Details_Inserted(Purchase_Detail entity)
{
//============== product Stock is changing here =======================
entity.Product.Stock_In_hand += entity.Quantity;
//adds this quantity to previous stock
}
partial void Purchase_Details_Updating(Purchase_Detail entity)
{
var value = (from val in Purchases
where val.Purchase_ID.Equals(entity.Purchase.Purchase_ID)
select val).FirstOrDefault();
value.Total = 0;
entity.Purchase = update_total(value); //if product detail value is changed then recount total and update it.
}