The basics of Linq
General-purpose query facilities added to the .NET Framework apply to all sources of information, not just relational or XML data. This facility is called .NET Language-Integrated Query (LINQ)
The local variable query is initialized with a query expression. A query expression operates on one or more information sources by applying one or more query operators from either the standard query operators or domain-specific operators. This expression uses three of the standard query operators: Where, OrderBy, and Select.