LINQ

Language-Integrated Query (LINQ) is a powerful query language introduced with .Net 3.5 & Visual Studio 2008. LINQ can be used with C# or Visual Basic to query different data sources.

LINQ (Language Integrated Query) is uniform query syntax in C# and VB.NET to retrieve data from different sources and formats. It is integrated in C# or VB, thereby eliminating the mismatch between programming languages and databases, as well as providing a single querying interface for different types of data sources.

For example, SQL is a Structured Query Language used to save and retrieve data from a database. In the same way, LINQ is a structured query syntax built in C# and VB.NET to retrieve data from different types of data sources such as collections, ADO.Net DataSet, XML Docs, web service and MS SQL Server and other databases.LINQ Usage

C# LINQ usage

LINQ queries return results as objects. It enables you to uses object-oriented approach on the result set and not to worry about transforming different formats of results into objects.

LINQ Query

The following example demonstrates a simple LINQ query that gets all strings from an array which contains 'a'.

// Data source
string[] names = { "Bill", "Steve", "James", "Mohan" };

// LINQ Query 
var myLinqQuery = from name in names
                where name.Contains('a')
                select name;
    
// Query execution
foreach(var name in myLinqQuery)
    Console.Write(name + " ");

In the above example, string array names is a data source. The following is a LINQ query which is assigned to a variable myLinqQuery.

from name in names
where name.Contains('a')
select name;