Not able to access TotalPrice in OrderItem

Question

Trying to write trigger on Order item .I have created new field called discount.I have to perform formula using trigger on TotalPrice(TotalPrice=Discount*TotalPrice).I am not able to access TotalPrice hence getting this error "Innvalid field TotalPrice for SObject OrderItem " Not understanding how to access TotalPrice fields .

 trigger Totalprice on OrderItem (after insert,after update)  {
      if(trigger.isafter && trigger.isupdate){
           for(OrderItem oi : trigger.new) {
               Oi.TotalPrice=  Oi.Discount__c*Oi.TotalPrice;
           }
      }
 }

Answer 1

The TotalPrice field is not available in OrderItem object it is being calculated

OrderItem.TotalPrice = OrderItem.UnitPrice * OrderItem.Quantity

so query for the quantity and unitprice and use above formula.

Hope this helps you.