Calling functions in Linq To SQl .net 3.5

guys How can i achieve the following

var productslist=from p in productsTable
                 select new product{Id=p.Id,Tax=myfunctions.calculateTax(p.price)};

i have tried to google and came across this document. Is there another way i can do this without using third party dlls

Solution: Move application to .net 4.0 (this is actually support and supposed to work). Nway i stuck to the below solution for the time being