Is there a "best practice" for where to put the code for calculated values stored in the properties of an object? Access methods are nice, but the calculations get executed a lot more often than necessary. In the interests of polymorphism, I thought about using a Calculate() method which is passed a code string (ie. oMyObject.Calculate("TAX")) to determine which calculation to perform. Although this provides a standard interface, I don't really think it meets the goals of polymorphism, since you have to know the code of each calculation you want to perform. Perhaps a custom method for each calculation is the best way to go (ie. oMyObject.CalcTax()). It does tell you exactly what the method does.

What do you think? Your opinion is appreciated.