Data Access Layer design patterns

Question

I have to design a Data Access Layer with .NET that probably will use more than one database management system (Mysql and Sql Server) with the same relational design.

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Answer 1

In general, I second John Nolan's recommendation of Patterns of Enterprise Application Architecture.

More specifically, I would always recommend that you hide your Data Access Layer behind an interface and use Dependency Injection to inject a particular Data Access Component into your Domain Logic at run-time.

You can use a Dependency Injection Container or do it manually.

On the technology side I would recommend Microsoft's Entity Framework, since your data access needs seem to be constrained to relational databases. The Entity Framework is Microsoft's official OR/M and it has providers for many different RDBMSs, as well as LINQ support.