c# - What is the difference between "LINQ to Entities", "LINQ to SQL" and "LINQ to Dataset"

Question

I've been working for quite a while now with LINQ. However, it remains a bit of a mystery what the real differences are between the mentioned flavours of LINQ.

The successful answer will contain a short differentiation between them. What is the main goal of each flavor, what is the benefit, and is there a performance impact...

P.S. I know that there are a lot of information sources out there, but I'm looking for a kind of a "cheat sheet" which instructs a newbie where to head for a specific goal.

Answer 1

• all of them are LINQ - Language Integrated Query - so they all share a lot of commonality. All these "dialects" basically allow you to do a query-style select of data, from various sources.

• Linq-to-SQL is Microsoft's first attempt at an ORM - Object-Relational Mapper. It supports SQL Server only. It's a mapping technology to map SQL Server database tables to .NET objects.

• Linq-to-Entities is the same idea, but using Entity Framework in the background, as the ORM - again from Microsoft, but supporting multiple database backends

• Linq-to-DataSets is LINQ, but using is against the "old-style" ADO.NET 2.0 DataSets - in the times before ORM's from Microsoft, all you could do with ADO.NET was returning DataSets, DataTables etc., and Linq-to-DataSets queries those data stores for data. So in this case, you'd return a DataTable or DataSets (System.Data namespace) from a database backend, and then query those using the LINQ syntax