Data Access Layer strategies

In a nutshell

• Use Unit of Work for coordinating queries and writes, ideally using an ORM such as Entity Framework or NHibernate
• Unit of Work and transactions should be explicit rather than implicit, for performance and expression of intent.
• Consider query objects over repository pattern
• Use LINQ and extension methods to create expressive, fluent queries
• Use ORM-specific features liberally; abstracting away the ORM is a lost cause.