Question

what is the difference between linq to sql classes and entity framework
seem that they same work like both
which is better in .net3.5 and why?
*which is better in .net4 and why?*

Answer 1

Briefly:

Linq-to-SQL is:

• a “proof-of-concept” done by the Visual C# team to show off the capabilities of Linq
• a straight 1:1 mapper – one table becomes one entity in your code
• for SQL Server only
• not very well suited to support stored procedures (you cannot e.g. create “complex types” to mirror values returned from your stored procedure)
• designer-driven, database-first only approach (and model cannot be easily updated if your database changes)
• basically a dead-end technology – there might be bug fixes here and there, but certainly no new features; it works – but don’t expect any further development on this

–> so Linq-to-SQL works, and quite well in .NET 3.5 – but don’t expect anything new here….

Entity Framework (at least in .NET v4 and up) is:

• a “proper” OR-mapper technology (and more) done by the ADO.NET/database teams at Microsoft
• a flexible mapper with a physical layer (database schema), a conceptual layer (your .NET objects), and a mapping layer between those two (three-layer approach)
• supports several databases (SQL Server, Oracle etc.) out of the box – fairly easy to write an Entity Framework compatible provider for other databases
• supports stored procedures very well (you can even pick a stored proc for one entity and one operation, e.g. for the DELETE)
• offer database-first, model-first and code-first development approaches
• if using model – that model can be updated from the database if your tables change over time
• the product that Microsoft is investing lots of their resources into – still being very actively developed (additional features, new approachs like code-first development etc.)

–> Entity Framework is my clear choice for .NET 4 and newer