Language Integrated Query (LINQ) is used to querying data from wide variety of data sources like databases, xml, objects etc. It is also pronounced as Link.
Features of LINQ
1) It is a query language that is an integrated feature of the developer’s primary programming languages, such as C# and Visual Basic, without the necessity of learning different databases and query languages.2) LINQ offers uniform way to access and manage data irrespective of data sources. For example, RDBMS, Object Collection, and XML etc.3) It allows query expression to benefit from compile-time syntax checking, static typing and intellisense which were previously available to only crucial code.4) It provides standard query operators which allow traversal, filter, and project operations to be expressed in .Net-based programming languages.
LINQ APIs
System.Linq namesapace provides classes and interfaces that support queries that use LINQ.System.Data.Linq namespace contains classes that support interaction with relational data in SQL Server databases.System.XML.Linq namespace contains the classes for working with XML data.
LINQ Architecture
The .NET applications can be coded using any .NET language. Applications can use LINQ. LINQ providers are going to convert LINQ query into a format that understood by underlying data sources.
LINQ Providers and Description
Below is the LINQ providers and description.
| LINQ Providers | Description |
|---|---|
| LINQ to Objects | It is used for querying in-memory collections. This provides the ability to query IEnumerable |
| LINQ to ADO.NET | It includes ‘LINQ to DataSet’ , ‘LINQ to SQL’ and ‘LINQ to Entities’. |
| LINQ to DataSet | It allows writing queries that take advantage of standard query operator for writing complex queries to query DataSet. |
| LINQ to SQL | This gives the ability to access relational database (SQL-Server) objects as normal .NET objects. LINQ to SQL integrates SQL schema based definitions to the common language runtime (CLR) type system. This provides strong typing, syntax checking, and intellisense over SQL objects, while retaining expressive power of relational model and performance of query evaluation directly in the underlying database. It performs data access and manipulation using a strongly-typed object-DataContext. Click here to read articles related to LINQ to SQL. |
| LINQ to Entities | It supports ADO.NET entity framework and allows querying a list of entities abstracted from physical data layer, using LINQ syntax. |
| LINQ to XML | It provides efficient, east to use, in-memory XML manipulation capabilities to provide XPath/XQuery functionality to programming languages using simple query operators. |
