LINQ: the new way to query

1
LINQ the new way to query

• LINQ Project (Language-Integrated Query) A
  general purpose query facility of the .NET
  Framework.
• Presented byDwight Barbour, dbs_at_dbsolutions.net
  http//www.eeicom.com/traininghttp//www.FederalA
  SP.org/202.250.3489
• NoVa Code Camp 2007

2
Dwight Barbour

• Educator
• GW, GT, UDC, USDA
• Independent Technology Schools
• Customized Training for Government, DoD,
  Non-profit and private industry
• Developer
• Data-driven Web Development
• Accessibility (Section 508, 1194.22 and W3C WAI)

3
Audience Check

• Developing for over 5 years?
• Works with data?
• Database
• XML source
• .NET Developer?
• ASP.NET?
• What language?

4
Code Samples

• ASP.NET with Visual Basic
• Samples are focused
• Slides and code are availableDrop me an email
  ltdbs_at_dbsolutions.netgt for the slides and code.
  If you email within a week, I'll send you a
  discount coupon for a class at EEI Training.
  http//www.eeicom.com/

5
Goals

• What is LINQ?
• How to get started
• .NET 3.0 Language EnhancementsDemos are in VB
  9.0 .NET Visual Basic Versions
  VB 9.0 VB.NET 3.0 VB 8.0 VB.NET 2.0
  VB 2005 VB 7.0 VB.NET 1.x VB 2003
• Introduction to the LINQ syntax
• Advanced Demos

6
Pre-LINQ Scenario

• PROGRAMMERS
• are becoming more productive with objects
• With objects we work faster. inheritance
  IntelliSensing

• TECHNOLOGIES
• SQL (a SQL string) to work with XML
• Xquery/XPath to work with XML
• Methods/Functions to work with in- memory
  objects

7
(1) What is LINQ?

• General purpose query facility of .NET Framework
• Applicable to multiple data sources
• Relational databases / DataSets
• XML
• In memory objects (array, hash, collection)
• Talk ClarificationWe are focusing on Query, but
  Create and Update capabilities exist too.

8
(2) How to get started

• Downloads Community Technology Preview (CTP) May
  2006 (or upgrade to 3.0)http//msdn.microsoft.com
  /XML/linqproject
• Installs (WARNING)
• Language Enhancements (VB C)
• LINQ Functionality
• Samples
• Documents
• LINQ Project Type
• Create a new LINQ Project Type

9
LINQ Project Type
10
(3) VB 9.0 Enhancements

• Type Inference (Implicit Typing)
• Anonymous Types
• Object Initializers

11
What is Type Inference (Implicit Typing)

• Type a data typeCommon types include primitive
  types (integers, floats, characters), classes,
  function types, etc.
• Inference guessingAct of deriving logical
  conclusion
• Implicit not stated, but understoodUnderstood
  though not directly expressed

12
Type Inference(Implicit Typing)

• ' VB8
• Dim state As String DC
• Dim states() As String DC, VA, MD
• ' VB9
• Dim state DC
• Dim states DC, VA, MDNOTE Type
  inference is determined at compile time, it is
  NOT late binding(runtime).

13
What areAnonymous Types

• Anonymous types lets you create variables of new
  types without first defining the type. Because
  the new type is never explicitly specified, it
  remains anonymous.
• Anonymous TypeHaving an unknown type.

14
Object Initializers

• Anonymous Types feature uses another VB9 feature
  called Object Initializers.
• Object Initializers let you initialize a complex
  data object within an expression.
• For the demo, think of this Customer Object
  (instance called cust1) cust1.Name
  cust1.City cust1.State

15
Object Initializers

• Object Initializer all fieldsDim cust1 As
  Customer New Customer NameJoe,
  CityNYC, StateNY
• Object Initializer some fieldsDim cust1 As
  Customer New Customer NameJoe,
  StateNY

16
Object Initializers withType Inference

• Left-Side Type Inference (infer Customer) Dim
  cust1 New Customer NameJoe,
  StateNY
• Right-Side Type Inference (infer Customer) Dim
  cust1 As Customer NameJoe,
  StateNY
• Both-Side Type Inference (infers Anonymous
  Type!) Dim cust1 New NameJoe,
  StateNY

17
(4) LINQ Syntax

• Basic Syntax
• Sorting
• Aggregate Operators (count, min, max, sum,
  average)
• Partitioning OperatorsSelect a portion of the
  collection by inclusion or exclusion.
• Element OperatorsChoose one specific element
  from the collection.

18
Basic Query Syntax

• Dim theNums 1, 10, 21, 2
• Dim underTen From n In theNums _ Where n lt 10
  _ Select n
• For Each Dim m In underTen label1.Text m
  Next
• Output 1 2
• Note Implicit Types theNums (integer array),
  underTen (IEnumerable of Integer), n (integer)

19
Sorting a Query

• Dim theNums 1, 9, 13, 7, 2
• Dim underTen From n In theNums _ Where n lt 10
  _ Select n _ Order By n
• Dim underTen From n In theNums _ Where n lt 10
  _ Select n _ Order By n Ascending
• Dim underTen From n In theNums _ Where n lt 10
  _ Select n _ Order By n Descending

20
Aggregate Operators (Count, Min, Max, Sum,
Average)

• Dim underTenCount Count( From n In theNums _
  Where n lt 10 _ Select n )
• Dim underTenCount ( From n In theNums _ Where
  n lt 10 _ Select n ).Count()Which form of the
  aggregate operator would you prefer?

21
Partitioning Operators Select a portion of a
collection by inclusion or exclusion.

• Dim underTenCount ( From n In theNums _ Where
  n lt 10 _ Select n _ Order By n ).Take(5)
• Dim underTenCount ( From n In theNums _ Where
  n lt 10 _ Select n _ Order By n ).Skip(5)

22
Element Operators Select a single element to be
returned.

• Dim firstFoundUnderTen ( From n In theNums _
  Where n lt 10 _ Select n ).First()
• Dim zeroBased ( From n In theNums _ Where n lt
  10 _ Select n ).ElementAt(5)Note Position 5
  is the index value. Positions are zero based.
  Position 5 is actually the 6th item.

23
(5) Advanced Demos

• Structured Data
• Multiple Source
• Group By

24
LINQ Review

• What is LINQ?
• It is used to....
• The installation installs...
• Benefits
• Transferable Knowledge
• IntelliSense

25
Dwight Barbourdbs_at_dbsolutions.net 202.250.3489

• Training needs? Custom dbs_at_dbsolutions.net,
  202.250.3489Open Enrolment
  http//www.eeicom.com/training/
• Free Traininghttp//www.FederalASP.org/http//w
  ww.eeicom.com/training/seminar_register.cfm