linq2db - LINQ to DB is the fastest LINQ database access library offering a simple, light, fast, and type-safe layer between your POCO objects and your database.
Architecturally it is one step above micro-ORMs like Dapper, Massive, or PetaPoco, in that you work with LINQ expressions, not with magic strings, while maintaining a thin abstraction layer between your code and the database. Your queries are checked by the C# compiler and allow for easy refactoring.
However, it's not as heavy as LINQ to SQL or Entity Framework. There is no change-tracking, so you have to manage that yourself, but on the positive side you get more control and faster access to your data.
In other words LINQ to DB is type-safe SQL..