LINQ - Language-Integrated Query - Basics in C# 3.0

LINQ - Language-Integrated Query - Basics in C# 3.0


-To indicate that query is an integrated feature of the developer's primary programming languages.
-Language-integrated query allows query expressions to benefit from the rich metadata, compile-time syntax checking,
static typing and IntelliSense that was previously available only to imperative code .
-The standard query operators allow queries to be applied to any IEnumerable-based information source.
-The extensibility of the query architecture is used in the LINQ project itself to provide implementations
that work over both XML and SQL data.
-The query operators over XML (LINQ to XML) use an efficient, easy-to-use, in-memory XML facility to provide XPath/XQuery
functionality in the host programming language.

simple C# 3.0 program

using System;
using System.Linq;
using System.Collections.Generic;

class app {
static void Main() {
string[] names = { "Burke", "Connor", "Frank",
"Everett", "Albert", "George",
"Harris", "David" };

IEnumerable query = from s in names
where s.Length == 5
orderby s
select s.ToUpper();

foreach (string item in query)
Console.WriteLine(item);
}
}

Output:

BURKE
DAVID
FRANK

-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.

Enumerable query = names
.Where(s => s.Length == 5)
.OrderBy(s => s)
.Select(s => s.ToUpper());