Generic Problem

Question

I design simple DAL using Generic i have 2 business objects matched to each other one in BusLayer and the other in DAL. DAL just deal with DAL.Domain.Categories BusLayer see Business.BusinessObject.Categorie and DAL.Domain.Categories DALProxy is a class in business layer and it the only class talk with DAL in Business Layer when developer need to get a recored from DB  he will write the following: public Business.BusinessObject.Categorie GetCategorie( string primKey) { DALProxy proxy = new DALProxy ( Connection string .... ); Business.BusinessObject.Categorie cat = proxy.GetRecord Categories >(primKey ); Return cat; } Then GetRecord Method in DALProxy call DAL DAO public T GetRecord ( object key) { DAO dao = new DAO (  ); T busObject = new T(); U domainObject = dao.GetRecord (key); // then map U to T before return T T busObject = Mapper.Map(domainObject busObject ); return busObject ; } My Question is how to make Proxy.get Record take just T not T and U. i mean developer not need to know the matching Domain object and type it. i need it to be implicit and to be my problem is explained well i have a stupid solution: in proxy getrecord i will check type of T if it a type of Categories then Call DAO.getRecord Categories> so i will have 150 if statments for each busobject any smart solution

Ahmed Soliman · Answer

it was one gatway in the firstfor ex i had 4 layer 1-business 2-DAL 3-presentation 4-domain (business objects) refererance rule as following: presentation -> business presentation -> Domain presentation -> DAL business -> DAL business -> Domain Domain -> DAl So it seems bad design presentation layer should see just Business layer which have business objects in the same layer. but since my business object is somehow complex and have logic and attriputes related to Dal i said developer not need to see all of these information he should see simple business object with getter and setter. Also in future if we need to create custom mapping between domain object and business object for ex( compine two domain object in one busobject or map column first name and last name to Full name column). so i suggested to be domain object in DAL and busobject in Business Layer. i found a solution to my problem i don't know it will fit in all cases or not: public abstract class BaseBusiness where Y : IDBTable  new() { public void GetRecord(object key) { DAO dao = new DAO(); Y domainObject = dao.GetRecord ((long)key); ObjectMapper.Map(domainObject this); } } public class Categories : BaseBusiness { // constructor public Categories(object key) { GetRecord(key); } } if you see my design is not good  give me your sugessions thanks at all

Matthew Cochran · Answer

The problem is that you have no place storing the relationship between the 'T' and 'U' types so you have to specify both. You could create a dictionary of mappings and keep it around (Dictionary ) but I think your solution will become very complex and hard to maintain. Can you refactor to totally encapsulate the DAO and all the DAO objects inside your business layer? People consuming your library should not have to deal with the DAO or even be aware of it. I'm not sure I understand the need to cerate a seperate DAO object just to map to a business object. It seems to be a lot of extra code with little benefit. You could probably simplify your solution by having one data gateway layer between the business objects and the database.