Introduction to LINQ

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Introduction to LINQ

• Ganesan Muthiah
• http//gmuthaia.wordpress.com/
• gmuthaia_at_live.com

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Introduction

• How do you interrogate/manipulate data?
• What if you could do the work in a type-safe,"
  string-free manner?
• What if you could use a consistent querying
  syntax for data, objects or XML?

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Agenda

• What is LINQ
• Queries without LINQ
• Key features of LINQ
• LINQ Architecture
• LINQ to

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What is LINQ?

• Language Integrated Query
• Make query a part of the language
• Component of .NET Framework 3.5

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Queries without LINQ
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Key Features of LINQ

• Delayed Execution
• LINQ queries don't execute until they must
• Retrieve specific values
• Iterate through the collection
• Perform an operation
• Write Data Access Code directly
• Compile time syntax and schema checking
  (intellisense too)
• no need of inline sql or to wait until runtime to
  see if it is ok
• LINQ data access code abstracted from underlying
  data
• consistent syntax across various data sources
• can join information from different sources.

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Architecture
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LINQ to

• LINQ to Objects
• LINQ to SQL (formerly known as DLINQ)
• LINQ to XML (formerly known as XLINQ)
• LINQ to Entities (ADO.NET Entities)

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LINQ to Objects

• Query any IEnumerableltTgt sourceIncludes arrays,
  ListltTgt, Dictionary...
• Many useful operators availableSum, Max, Min,
  Distinct, Intersect, Union
• Expose your own data with IEnumerableltTgt or
  IQueryableltTgt
• Create operators using extension methods

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LINQ to Objects

• DEMO

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LINQ to SQL (formerly known as DLinq)

• Object-relational mapping (ORM)
• Records become strongly-typed objects.
• Includes tracking of changed objects and
  persistence.
• Ensures that you will not obtain multiple objects
  for the same underlying row in the database (
  Fowlers Identity Map)
• Data context is the controller mechanism
• Facilitates update, delete insert
• Type, parameter and injection safe

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LINQ to SQL

• DEMO

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LINQ to XML (formerly known as XLinq)

• Similar to LINQ to SQL but along the idea of
  querying XML documents using LINQ syntax rather
  than the XPath/XQuery syntax.

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LINQ to XML

• DEMO

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LINQ to Entities

• LINQ to Entities (ADO.NET Entities)
• A more advanced ORM solution that allows more
  extensive mapping and manipulation between how
  the object appears and the underlying data
  source.
• LINQ to Entity provides
• Excellent build support if it isn't mapped
  100, it won't build
• It works with other databases (I'm currently
  using it with Oracle)
• It properly seperates the structural model from
  the conceptual entity model.
• It maps many to many relationships properly.

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LINQ to Entities

• DEMO

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Summary

• Had a quick intro on
• LINQ and its need
• Key Language features
• LINQ Architecture
• LINQ Types
• LINQ Operators

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For more information.

• Official site
• http//msdn.microsoft.com/en-us/netframework/aa904
  594.aspx
• Tutorials
• http//weblogs.asp.net/scottgu/archive/tags/LINQ/d
  efault.aspx
• 101 LINQ Samples
• http//msdn.microsoft.com/en-us/vcsharp/aa336746.a
  spx
• LINQ Pad
• http//www.linqpad.net/

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• Thank you
• Questions?