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What is LINQ?

What is LINQ?. Language Integrated Query Make query a part of the language Component of .NET Framework 3.5 Shipped with Visual Studio 2008.

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What is LINQ?

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  1. What is LINQ? • Language Integrated Query • Make query a part of the language • Component of .NET Framework 3.5 • Shipped with Visual Studio 2008

  2. Linq is short for Language Integrated Query. If you are used to using SQL to query databases, you are going to have something of a head start with Linq, since they have many ideas in common.

  3. LINQ provides a high-level abstraction of virtually any data and emulates the query operations of the relational model.

  4. Language Integrated Query (LINQ, pronounced "link") is a Microsoft.NET Framework component that adds native data querying capabilities to .NET languages.

  5. LINQ (often overheard pronounced as "link") is a step in the evolution of data access. It is a programming model that brings a much needed uniformity to accessing data from files, XML, database, registry, event log

  6. LINQ • Allows to perform iterations on Collections • Main namespace is System.core

  7. Query with LINQ C#var myCustomers = from c in customers where c.Region == "UK" select c;

  8. Advantages • Unified data accessSingle syntax to learn and remember • Strongly typedCatch errors during compilation • IntelliSensePrompt for syntax and attributes • Bindable result sets • More evident when more complex filters are present

  9. Architecture C# VB.NET Others .NET Language Integrated Query (LINQ) LINQ data source providers ADO.NET support for LINQ LINQto Objects LINQto Datasets LINQto SQL LINQto Entities LINQto XML

  10. LINQ to Objects • C#int[] nums = new int[] {0,4,2,6,3,8,3,1};double average = nums.Take(6).Average();var above = from n in nums where n > average select n; • Filtering process is easy because of the Intellisense feature

  11. LINQ to Objects • Use of Ienumerable <T> or Iqueryable<T> collection • Query any IEnumerable<T> sourceIncludes arrays, List<T>, Dictionary... • Instead of for each loops or iterative loops the condition of LINQ used along with Ienumerable helps in rapid data retrieval

  12. LINQ operators and many others

  13. LINQ to Dataset • LINQ to dataset is build on the top of ADO.Net to simplify the tasks • Ensure that a reference System.Data.DataSetExtensions.dll is added • Typed dataset feture is present(Fields) • Reshaping data with Anonymous type feature

  14. LINQ to Entities • What is the Entity Data Model? Definition for your application model Map between app model, database schema Advanced mapping scenarios supported One entity mapped across multiple tables • Multiple inheritance hierarchy mappings • Many-to-many without "link" table in model

  15. LINQ to Entities or LINQ to SQL? • LINQ to SQL • Shipped with Visual Studio 2008 and .NET 3.5 • Emphasis on rapid application development • Supports Microsoft SQL Server family of databases • LINQ to Entities • Will ship as an update to .NET 3.5 • Offers a provider model for third-party databases • Designed for enterprise-grade data scenarios • Higher level of abstraction for programming databases • Just one layer of the overall ADO.NET Entity Framework

  16. LINQ to Entities: Generating Queries • Converting LINQ queries to SQL • Compiler converts code into a LINQ expression tree • LINQ to Entities converts LINQ expression tree into a DbCommandTree based on mapping information • DbCommandTree expressed in terms of the database schema • ADO.NET provider generates a DbCommand • LINQ to Entities executes the DbCommand, assembles results into the structure(s) specified in the LINQ query

  17. Entity Framework Query Options • EntityClient Provider string"SELECT VALUE o FROM NorthwindEntities.Orders AS o " + "WHERE o.Customers.CustomerID = 'ALFKI'"; EntityCommandnewEntityCommand(eS EntityDataReader = while ( Console. ("{0} {1:d}", ["OrderID"], ["OrderDate"]);

  18. LINQ to SQL • Object-relational mappingRecords become strongly-typed objects • Data context is the controller mechanism • Facilitates update, delete & insert • Translates LINQ queries behind the scenes • Type, parameter and injection safe

  19. Instead of manipulating the database directly,developers manipulate the object model,which represents the database • For this,Windows application must be created • Add new LINQ to SQL class items to the project • Drag and drop tables and make changes .It will be saved only in the object model • To save changes in the database use the following syntax • Database.Submitchanges();

  20. Database mapping • VS 2008 designer or SQLMetal command • Map tables & fields to classes & properties • Generates partial classes with attributes • Each record becomes an object • Data context represents the database • Utilise tables, views or stored procedures

  21. Modifying objects • UpdateSet object properties • Deletecontext.Table.DeleteOnSubmit(object) • Insertcontext.Table.InsertOnSubmit(object) • Commit changes backcontext.SubmitChanges()Transactional - all or nothing

  22. LINQ is beneficial than Stored Procedures • Debugging(Complex dedug in SP) • Deployment(.dll) • Type Safety (Errors)

  23. LINQ and Extension Methods • Extend functionality to an existing class without needing to subclass it • To add extension methods to objects implementing the Ienumerable interface,you need a reference to system.core.dll

  24. LINQ TO XML Earlier Xpath or Xquery were used to manipulate XML documents, at present LINQ to XML concepts are used Add a reference to the System.xml.linq.dll in the project and also import System.xml.linqnamespace Tree -> Xdocument ->XElement ->XAttribute LOAD XDocumentLibraryBooks = new Xdocument(); LibraryBooks = Xdocument.load(“Books.xml”);

  25. Future developments • BlinqScaffold web UI for list/view/update pages • PLINQParallel query processing over many CPUs • SyncLINQ & Continuous LINQUpdated results via INotifyCollectionChanged

  26. PLINQ • Microsoft, as a part of the Parallel Extensions, is developing PLINQ, or Parallel LINQ, a parallel execution engine for LINQ queries. It defines the IParallelEnumerable<T> interface. If the source collection implements this interface, the parallel execution engine is invoked. The PLINQ engine executes a query in a distributed manner on a multi-core or multi-processor system.[28]

  27. .NET features used .NET Framework 3.5 • Anonymous types (shaping) • Extension methods (query operators) • Type inference (var keyword) • Lambda expressions (query syntax)

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