text: object_orientation in vb.net? i have got a program where i should extensively implement object-oriented features of the vb.net. i have got a class tenant and a class room, both belong to some dormitory. in that dormitory class i have 2 array lists to store objects of class tenant and room respectively. in class tenant i created association with the class room, so i may see in which room every tenant lives. however i did not create association in the room class in order to avoid data duplication.    instead if i want to lookup which tenant lives in some particular room, i first get the room number from the rooms array list and then i lookup the same room no in the tents list and retrieve the corresponding tenant's name.   i am not sure whether this approach is fine, anyway it provides me info i need. but i am not sure whether it is object oriented enough? should i create an association to tenant class in the room class?   someone told me that class should be a complete entity and hold all the info it is suppos i think your approach is fine, but if you want to learn to use oo you should read a design patterns book, or the book by the gang of 4 erich gamma, richard helm, ralph johnson, and john vlissides.  you can check out this site or get newer books that cover this in .net or java   i agree that oo just for no reason makes the code hard to understand, but in some cases it can save you a lot of work on the long run.  design patterns are proven solutions to reoccurring problems in software, so why re-invent the wheel.  if you want to see patterns in action in .net you can look at the source code for enterprise library for .net framework 2.0.