I work on a C# client application (SlimTune Profiler) that uses relational (and potentially embedded) database engines as its backing store. The current version already has to deal with SQLite and SQL Server Compact, and I’d like to experiment with support for other systems like MySQL, Firebird, and so on. Worse still, I’d like it to support plugins for any other backing data store — and not necessarily ones that are SQL based, ideally. Topping off the cake, the frontend itself supports plugins, so I have an unknown many-to-many mapping between querying code and engines handling the queries.
Right now, queries are basically handled via raw SQL code. I’ve already run into trouble making complex SELECTs work in a portable way. The problem can only get worse over time, and that doesn’t even consider the idea of supporting non-SQL data. So then, what is the best way to query wildly disparate engines in a sane way?
I’ve considered something based on LINQ, possibly the DbLinq project. Another option is object persistence frameworks, Subsonic for example. But I’m not too sure what’s out there, what the limitations are, or if I’m just hoping for too much.
(An aside, for the inevitable question of why I don’t settle on one engine. I like giving the user a choice of the engine that works best for them. SQL Compact allows replication to a full SQL Server instance. SQLite is portable and supports in-memory databases. I can imagine a situation where a company wants to drop in a MySQL plugin so that they can easily store and collate an application’s performance data over the course of time. Last and most importantly, I find the idea that I should have to be dependent on the implementation details of my underlying database engine to be absurd.)
Use an object-relational mapper. This will provide a high level of abstraction away from the different database engines, and won’t impose (many) limitations on the kind of queries you can run. Many ORMs also include LINQ support. There are numerous questions on SO providing recommendations and comparisons (e.g. What is your favorite ORM for .NET? appears to be the most recent and has links to several others).