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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
What is LINQ?
  • Language Integrated Query
  • Make query a part of the language
  • Component of .NET Framework 3.5
  • Shipped with Visual Studio 2008
slide2

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.

slide3

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

slide4

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

slide5

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

slide6
LINQ
  • Allows to perform iterations on Collections
  • Main namespace is System.core
query with linq
Query with LINQ

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

advantages
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
architecture
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

linq to objects
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
linq to objects1
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
linq operators
LINQ operators

and many others

linq to dataset
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
linq to entities
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
linq to entities or linq to sql
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
linq to entities generating queries
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
entity framework query options
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"]);

linq to sql
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
slide20

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();
database mapping
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
modifying objects
Modifying objects
  • UpdateSet object properties
  • Deletecontext.Table.DeleteOnSubmit(object)
  • Insertcontext.Table.InsertOnSubmit(object)
  • Commit changes backcontext.SubmitChanges()Transactional - all or nothing
linq is beneficial than stored procedures
LINQ is beneficial than Stored Procedures
  • Debugging(Complex dedug in SP)
  • Deployment(.dll)
  • Type Safety (Errors)
linq and extension methods
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
linq to xml
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”);

future developments
Future developments
  • BlinqScaffold web UI for list/view/update pages
  • PLINQParallel query processing over many CPUs
  • SyncLINQ & Continuous LINQUpdated results via INotifyCollectionChanged
slide28

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]
net features used
.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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