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Note

Strictly speaking, “LINQ” is the term used to describe this overall approach to data access. LINQ to

Objects is LINQ over objects implementing 

IEnumerable

, LINQ to SQL is LINQ over relational data, LINQ to

DataSet is a superset of LINQ to SQL, and LINQ to XML is LINQ over XML documents. In the future, you are sure

to find other APIs that have been injected with LINQ functionality (in fact, there are already other LINQ-centric

projects under development at Microsoft).

LINQ Expressions Are Strongly Typed and Extendable

It is also very important to point out that a LINQ query expression (unlike a traditional SQL state-

ment) is 

strongly typed. Therefore, the C# compiler will keep us honest and make sure that these

expressions are syntactically well formed. On a related note, query expressions have metadata rep-

resentation within the assembly that makes use of them. Tools such as Visual Studio 2008 can use

this metadata for useful features such as IntelliSense, autocompletion, and so forth.

Also, before we dig into the details of LINQ, one final point is that LINQ is designed to be an

extendable technology. While this initial release of LINQ is targeted for relational databases/

DataSets, XML documents, and objects implementing IEnumerable, third parties can incorporate

new query operators (or redefine existing operators) using extension methods (see Chapter 13) to

account for addition forms of data.

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