Question

I got confused on what are the differences between Linq-to-SQL and Entity Framework when following the database first approach as I can not find any clear differences.

In my case when I was using Linq-to-SQL I used to create the tables then I use Linq-to-SQL to create the classes that represents the tables, and now when I switch to Entity Framework I am still following the same steps (creating the database tables then create the associated classes using EF).

And I am interacting with these classes on the same way, for example I used to query the User class using the same syntax and approach but one time when the User class was created using Linq-to-SQL and the other time when it was created using EF, so where is the difference ?

        public IQueryable<User> findstudents(string term)
        {
            return from student in entities1.Users
                   where student.UserID.Contains(term)
                   select student;

        }

Second question if I use EF to map the tables into classes, is it still possible to use Linq-to-SQL in the same application to query the EF classes?

Answer 1

LINQ is a base technology – that’s the syntax that gives you the SQLish query options in C# – that’s totally independent of whether you use Linq-to-SQL or EF. So if you want to query your data classes using the LINQ syntax – you can do that with both frameworks – but once you use Linq-to-SQL and once you use Linq-to-Entities. You cannot use Linq-to-SQL against an Entity Framework EDMX model.

Linq-to-SQL is great

• if you need very simple 1:1 mapping – one table equals one class in your domain model
• if you never need anything else but SQL Server (Linq-to-SQL doesn’t support anything else)
• if you want to be up and running really quickly

Entity Framework on the other hand

• supports multiple backends (SQL Server, Oracle, Firebird – other will likely follow)
• supports a full conceptual data modelling strategy – you define the physical model in the database, the conceptual model in your app, and the mapping between the two
• gives you the ability to handle things like mapping a single business entity to several tables
• support table-per-hierarchy and table-per-class inheritance scenarios
• support refreshing/updating your model (EDMX file) from the database when things change (in Linq-to-SQL, you basically have to drop + recreate those entities involved – thus loosing all your customizations you might have made)

In brief: Linq-to-SQL is a great, simple and lean’n’mean ORM for SQL Server – use it, if it does all you need. Entity Framework is quite a different beast, much more capable, but also more complex, much bigger – perfect for your next enterprise-critical app, but probably overkill for your personal blog app 🙂

If you want to create something that’s “future-proof” and will use the OR technology that Microsoft is pushing into the future, then you should go with Entity Framework. Especially in v4, it’s also a lot easier to use, a lot more slimmed down and more useful than ever before.