LINQ to SQL is an object relational mapping implementation that ships in Visual Studio 2008. It allows you to model a relational database using .NET classes.  You can then query the database using LINQ, as well as update/insert/delete data from it.

There have been many attempts in the past to develop technology that attempts to resolve the "impedance mismatch" that exists between relational database processing and object-oriented programming (see Object-relational mapping). Microsoft has entered this market with the introduction of LINQ to SQL that is available in all the Visual Studio 2008 products).

This set of videos provides an introduction to LINQ to SQL using Visual Basic 9.0. It uses the Northwind database in the example code. It also uses Visual Basic Express 2008 and SQL Express that are available at no cost from Microsoft.