Hey guy , i would like to know that how to implement the relationship many to many in O/R mapping. In the book the relationship between category and product is one to many, however if i want to modify the relationship between the category and product to many to many i.e. create a new table called categoryproduct which contains foreign key from categoryID and productID how could i implement those categorydetails and productdetails objects. Will i need to implement the mapping object categoryproduct as well.

Thank you very much for you help

It depends on how many records you want to deal with at a time. If you'll only have a small number of records you can denormalize the data and store it all in one class, or a couple classes. You have to decide how you want to map the domains so the data presentation layer will find it convenient to use, and the DBMS layer will find it efficient and reliable.

By the way, the term ORM usually refers to a slightly different process where you have a set of maps and an automated process to statically or dynamically map a table or set of tables to a domain class, or set of classes. Marco is using a custom DAL that isn't really an ORM methodology. Marco has defined his own classes by hand, which is the way a lot of people prefer to do it.

Eric

Hi englere, so how can i do it by hand based on Macro style

If you do it by hand you just design your own classes using traditional OOP technicques. Sometimes you'll see the term OOAD, which means Object Oriented Analysis and Design. Plug this into google.

If you're weak on the C# language you should get a good book on it. Marco's book assumes people already have some familiarity with OOP design methods.

The single biggest reason people have a hard time with .NET is because they don't really understand OOP. OOP is fundamental to .NET and it's worth it for you to learn it really well.

Eric