.net - Best design pattern for calculated values on a subclass? -

say have 2 types:

classa {     int valuea;     int calculateda; }  classb {     int valuea;     int calculateda;      int valueb;     int calculatedb; } 

calculatedb requires valuea valueb. i'm trying decide best pattern implement this.

option 1: subclass classa , add values. have common update() method overridden in subclass. simple code in model, code create these classes needs know create in advance, , code iterates on list of these types needs type checking deal fields.

option 2: have properties in separate class, , have update code calculatedb there. issue classb needs way of knowing when valuea updated, , hoping not have implement inotifypropertychanged on these classes. way have sort of public update method on properties class, , have main class call method when valuea updated. not desirable.

option 3: have classb valueb , calculatedb being nullable types. pass.

are there more? choose?

if classb not related classa, subclassing not method. btw, in .net don't expose public fields, public properties (assume c#)

public class classa{     public int valuea {get;set;}     //... } 

since classb.calculateb heavily rely on valuea, why not calculate value on fly, don't have worry property changing.

public class classb {     public int valueb {get;set;}     public int getcalculateb(classa a){         //...     } }