Choose your ORM: Runtime, code generation or build provider?
Selecting the right object-relational mapper is a tricky decision with many factors to weigh up.
One of the basic decisions is whether to go with a dynamic runtime (“black-box”) or a code generator.
I’m not a fan of the runtime approach – the discovery at runtime negatively impacts performance as it often uses reflection (or failing that post-compilation byte code modification) whilst robbing you of compile-time checking, IntelliPrompt support against your database objects, deployment and potentially licensing issues. In effect, it’s not that much better than a typed dataset.
Code generation provides for a much finer granularity letting you tweak the templates for the performance and features you need whilst also providing full compile-time checking and IntelliPrompt support.
Tools such as CodeSmith (my personal favourite), MyGeneration (free) do a good job of letting you write these templates and create the necessary ORM code but require being re-run every time you change the schema. During the starting phases of a project this could be quite often and goes against the whole concept of RAD.
So step in SubSonic and it’s build provider approach.
The idea here is that you modify your .config file to include the SubSonic build provider and it’s connection string, drop a simple text file in that lists which tables to work with and you’re done.
SubSonic now goes off to your database via the connection and generates all the code for tables you need and it’s magically there to be used like any other classes. Check out the demo to see just how easy it is.
SubSonic supports a large number of databases, has support for Enterprise Library, is open source and also provides simple “scaffold” pages that let you throw a basic web add/edit/update/delete table maintenance page by just throwing a table name attribute onto an empty page’s form element.
The only downside at this point is that it uses the ActiveRecord pattern for the ORM. If I manage to get some time to spend with it and can knock up a Domain Object + Data Mapper version I’ll let you know.