Linq to SQL
An object-oriented language such as C# and a SQL relational database have different views of the world. This is sometimes known as an impedance mismatch. The concepts of an object in C# and a row in a database seem very analogous, and there have been many attempts to unify them, with Linq to SQL being one of the more successful ones.
Linq to SQL is a very big topic, and covering it thoroughly requires a full book.1 This chapter is an introduction to using Linq to SQL.
Connecting by Hand
Before there was support to make things easier, a considerable amount of code was written to access databases by hand, something like the ...