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C sharp 3.0

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Implicit variable declaration

Anonymous Types

Extension Methods

Automatic Properties

Object Initializers

Collection Initializers

ambda Expressions !uery Expressions

Expression Trees

I"! to Collections

I"! to #ata$et

I"! to $!

Partial Methods

I"! to %M

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Implicit variable declaration

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Implicit declaration

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Only &ithin method can declare this"ot even &ith inter'aces also

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"ot even as parameter also

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Ta(e home o' Implicit )ariable

*or local stac( based variables

Its nothin+ li(e late bindin+ or anythin+ o' that (ind,

Compiler is in'ers the type,

$tron+ly associate- lin(ed or used &ith Anonymous type

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Anonymous Types

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Anonymous Types

Anonymous Types allo& you to create a class structure

on the 'ly,

It uses Implicit )ariables

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Creatin+ arrays o' Anonymous Types

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Anonymous type +els and &or(s &ell

&ith the ambda Expressions

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Extension Methods

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Extension Methods

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Extension Methods

Extension methods allo& developers to add ne& methods to thepublic contract o' an existin+ C. type- &ithout havin+ to sub/class

it or recompile the ori+inal type,

Extension methods are a ne& 'eature that allo&s you to enhance an

existin+ class by addin+ a ne& method to it &ithout modi'yin+ the

actual code 'or the class, This is especially use'ul &hen usin+ I"!

because several extension methods are available in &ritin+ I"!0uery expressions,

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"ote ho& the static method above has a 1this1 (ey&ord be'ore the 'irst parameter

ar+ument o' type strin+, This tells the compiler that this particular Extension Method

should be added to objects o' type 2int1,

Only public ones +ets extended

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Automatic Property

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Note about that we aren't actually adding any logic in the getters/setters of

our properties instead we just get/set the value directly to a field.

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Automatic Properties

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3hen the C4 1Orcas1 compiler encounters an empty +et5setproperty implementation li(e above- it &ill no& automatically+enerate a private 'ield 'or you &ithin your class- and

implement a public +etter and setter property implementationto it,

3ith the C4 and )6 1Orcas1 compilers you can no& ta(eadvanta+e o' a +reat 1syntactic su+ar1 lan+ua+e 'eature called1object Initializers1

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object Initializers

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Object Initialization &ith Complex

Type

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Collection Initializers

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Collection Initializer

Initial the collection in a sin+le line o' code,

Collection need to implement Icollection7T8

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As +ood as doin+ obj,add9: in the bac(+round

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!uery Expression

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I"!an+ua+e/Inte+rated !uery

9I"!:

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I"! an+ua+e

an+ua+e/Inte+rated !uery 9I"!: is a +roundbrea(in+innovation in )isual $tudio ;

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Traditionally

Traditionally- 0ueries a+ainst data are expressed assimple strin+s &ithout type chec(in+ at compile time orIntelli$ense support,

*urthermore- you have to learn a di''erent 0uery

lan+ua+e 'or each type o' data source> $! databases-%M documents- various 3eb services- and so on,

I"! ma(es a 0uery a 'irst/class lan+ua+e construct in

C4 and )isual 6asic, ?ou &rite 0ueries a+ainst stron+lytyped collections o' objects by usin+ lan+ua+e (ey&ordsand 'amiliar operators,

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The following illustration shows apartially-completed LINQ queryagainst a SQL Server database in Cwith full type chec!ing and

IntelliSense support"

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I"!

In )isual $tudio you can &rite I"! 0ueries in )isual6asic or C4 &ith $! $erver databases- %M

documents- A#O,"ET #atasets- and any collection o'

objects that supports IEnumerable or the +eneric

IEnumerable79O' 79T8:8:inter'ace,

I"! support 'or the A#O,"ET Entity *rame&or( is also

planned,

I"! providers are bein+ &ritten by third parties 'or

many 3eb services and other database

implementations,

http://msdn2.microsoft.com/en-us/library/h1x9x1b1.aspxhttp://msdn2.microsoft.com/en-us/library/9eekhta0.aspxhttp://msdn2.microsoft.com/en-us/library/9eekhta0.aspxhttp://msdn2.microsoft.com/en-us/library/h1x9x1b1.aspx

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Introduction to I"! !ueries

A 0uery is an expression that retrieves data 'rom a datasource, !ueries are usually expressed in a specialized0uery lan+ua+e, 9example $! 'or relational databasesand %!uery 'or %M, :

There'ore- developers have had to learn a ne& 0uerylan+ua+e 'or each type o' data source or data 'ormat thatthey must support,

"#N$ si!plifies this situation by offering aconsistent !odel for wor%ing with data acrossvarious %inds of data sources and for!ats.

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Ta(e @ome

In a I"! 0uery- you are al&ays &or(in+ &ith objects,

?ou use the same basic codin+ patterns to 0uery and

trans'orm data in %M documents- $! databases-

A#O,"ET #atasets- ,"ET collections- and any other'ormat 'or &hich a I"! provider is available,

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Three Parts o' a !uery Operation

All I"! 0uery operations consist o' three distinct actions>

Obtain the data source,

Create the 0uery, Execute the 0uery,

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T ( h ;

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Ta(e home ;

The 'rom clause speci'ies the data source- the &here

clause applies the 'ilter- and the select clause speci'ies

the type o' the returned elements,

The 0uery variable itsel' only stores the 0uery

commands, The actual execution o' the 0uery is de'erred

until you iterate over the 0uery variable in a foreach

statement, This concept is re'erred to as deferred

e&ecution.

i # di t ( ti

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orcing #!!ediate (&ecution

!ueries that per'orm a++re+ation 'unctions over a ran+e

o' source elements must 'irst iterate over those

elements, Examples o' such 0ueries are Count- )a&-

*verage- and irst, These execute &ithout an explicit'oreach statement because the 0uery itsel' must use

'oreach in order to return a result, "ote also that these

types o' 0ueries return a sin+le value- not an

#(nu!erablecollection,

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i # di t ( ti

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orcing #!!ediate (&ecution

!ueries that per'orm a++re+ation 'unctions over a ran+e

o' source elements must 'irst iterate over those

elements, Examples o' such 0ueries are Count- )a&-

*verage- and irst, These execute &ithout an explicit'oreach statement because the 0uery itsel' must use

'oreach in order to return a result, "ote also that these

types o' 0ueries return a sin+le value- not an

#(nu!erablecollection,

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The Collection Initializer

Expression !uery Anonymous

Type Implicit variable AutomaticProperty

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Automatic Property

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Collection initializer

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!uery expression

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#!plicitly +yped ,ariable.

*nony!ous +ypes

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$ummary

*s developers we now have a !uch

!ore concise way to define objects-initialie the!- and add the! to

collections

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ambda Expression

C 3 0 "anguage (nhance!ents for "#N$

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C 3.0 "anguage (nhance!ents for "#N$

To truly understand much o' the syntax o' I"!- it is

necessary 'or me to cover some o' the ne& C4 B,

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ambda Expressions

In C4 B,

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This method should have na

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sin+ ambda Expressions to Create

Expression Trees

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I"! treats data as objects,

"#N$ provides the ability to treat e&pressions as data at

runti!e.

"#N$ de'ines a ne& type- (&pression+1- &hich represents an

expression tree- an in/memory representation o' a lambdaexpression,

Expression trees allo& developers to treat lambda expressions as

data- allo&in+ 'or inspection and modi'ication o' lambda expressionsin code,

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"#N$ provides the ability to treat expressions as data at runtime, "#N$de'ines a ne& type- (&pression+1- &hich represents an expression tree-

an in memory representation o' a lambda expression

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an in/memory representation o' a lambda expression,

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Actually &e converted an expression tree into a dele+ate that can be executed

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It is very easy to create and build expressions that can be compiled

dynamically and create ne& uncobjects that pass around code as objects

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Conclusion On expression Tree

a database access implementation mi+ht levera+e this 'acility

to translate expression trees into suitable 0uery statements

'or a particular (ind o' database,

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"o int is re0uired as a result lambda has ed+e over dele+ate

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+he end