Here is a CodeProject article, called Top 10 Must Have Features for O/R Mapping Tools, written by a co-founder of AlachiSoft- a company that sells the TierDeveloper .NET O/R Mapper. I am sure it is written to help market their product, but if you are new to O/R Mappers it is a pretty good article about the basics. Read the full article.
Here is the authors Top 10 Must Have Features for O/R Mapping Tools:
- Flexible object mapping
- Use your existing domain objects
- Transactional operations (CRUD)
- Relationships and life cycle management
- Object inheritance
- Static and dynamic queries
- Stored procedure calls
- Object caching
- Customization of generated code
- Template customization
Those seems reasonable to me at first glance.
The author also has a fairly decent description of What is O/R Mapping:
“If you’re developing an object oriented application that requires a relational database, you’ll need to develop persistence objects that are modeled against your database design and know how to interact with different tables in the database. You can either develop these objects by hand or use an O/R mapping tool to map and generate them quickly. Hopefully, after reading this article, you’ll be convinced that developing by-hand is a bad idea in most situations.
An O/R mapping tool connects to your database and reads its schema, then lets you map persistence objects to database tables and views, specify single-row transactional operations, queries, and stored procedure calls as methods to these objects. And, it also lets you define one-to-one, one-to-many, many-to-one, and many-to-many relationships between objects based on relationships in the database. It then generates fully working persistence objects code for you...”
Here are some resources for .NET O/R Mappers and .NET Code Generators on my blog that you may find of interest: