What is the difference between Entity Framework and LINQ to SQL by .NET 4.0?

Question

I was checking 2nd edition of Professional ASP.NET MVC and realized EF replaced LINQ to SQL. I am familiar to LINQ to SQL from the first book but I know nothing about EF. An

Answer 1

EF came of age with v4.0. Before that, it was a bit of a pain to use, and I didn't recommend it. Now my recommendation is that all new LINQ-to-DB code use EF4.

As far as new features go, the LINQ part is actually quite similar to LINQ to SQL. But it's quite a different architecture: EF4 acts as a LINQ provider to an (EF) ADO.NET provider which then wraps another ADO.NET provider. So there's new things like Entity SQL (which I don't use), and EF supporting different underlying ADO.NET providers (which I do use).

The XML modeling system that EF uses allows more powerful mapping abstractions, as well. One that I use regularly is having different tables with the same primary keys mapping to an entity inheritance relationship; from what I understand, the only way to do this in LINQ to SQL is via a "selector column" (though I never tried this in LINQ to SQL).