Windows Mobile Support

  • Subscribe to our RSS feed.
  • Twitter
  • StumbleUpon
  • Reddit
  • Facebook
  • Digg

Sunday, 20 May 2012

The secret behind "params" keyword

Posted on 03:13 by Unknown
Jucandu-ma putin cu codul din C# am redescoperit "params". Acesta in general poate sa fie gasit intr-o aplicatie consola in Main, dar putem sa il folosim si in alte cazuri.
Prin intermediul acestui keyword putem sa specificam o lista de parametri despartiti prin virgula.
public void MyMethod(params string[] words)
{
foreach(string word in words)
{
Console.WriteLine(word);
}
}
Nu este nimic special cu acest keyword. Cand am inceput sa invatam limbajul C#, am vazut ca exista, dar nu l-am vazut niciodata folosit intr-un cod de productie si mi-am pus intrebarea DE CE?
In primul rand vrea sa vedem ce putem face cu acesta. De exemplu avem o metoda care accepta zero, unu sau mai multe elemente de acelasi tip (o lista de elemente). In mod normal am avea urmatorul cod:
public void MyMethod(string[] items)
{
// Some action.
}
Pentru a putea folosi aceasta metoda am avea urmatoarele apeluri:
MyMethod();    // Eroare la compilare.
MyMethod(new string[0]); // Nici un element in lista.
MyMethod(new string[]{ "item1" }); // Un singur element in vector.
MyMethod(new string[]{ "item1", item2" }); // Doua elemente in vector.
Ca sa putem avea si un apel de forma "MyMethod();" este nevoie sa schimba definitia metodei, ca sa aibe urmatoarea forma:
public void MyMethod(string[] items = null)
{
// Some action.
}
Daca ne-am folosii de keyword-ul params am avea urmatoare metoda si apeluri acceptate:
public void MyMethod(params string[] items)
{
// Some action.
}
MyMethod();
MyMethod("item1");
MyMethod("item1", "item2");
MyMethod(new string[0]);
MyMethod(new string[]{ "item1", item2" });
Dupa cum putem observa, putem sa avem diferite apeluri, putem sa specificam un sigur element, fara sa fim obligati sa ne definim un vector cu un singur element. La fel putem sa ne specificam nici un parametru, caz in care vectorul o sa fie un vector cu nici un element. In acez caz ne-am astepta ca vectorul sa fie null, dar acesta nu o sa fie null, nu o sa contina nici un element (aveti grija la acest comportament).
O alta utilizare interesanta a acestui keyword mi s-a parut in contructor. Da, in contructor, il putem folosi fara nici o problema si in constructori.
public class Foo
{
public Foo(paramas string[] items)
{
// Ceva cod
}
}
params este foarte util cand avem cazui cand elementele din vector pot sa contina 0 sau doar un element, iar aceste valori sunt obtinute din divese surse (nu le obtinem mereu sub forma unui vector).
Am vazut ce putem facem cu acest keyword, unele cazuri cand acesta se poate folosi sunt chiar interesante (nici un element specificat, un singur element fara sa ne declaram un vector sau in contructor). Problema apare ca din cauza ca nu este destul de des folosit in general cel care citeste codul o sa fie nevoit sa caude pe net sa vada ce reprezinta acest keyword sau de ce este folosit intr-un anumit fel. Tot din aceasta cauza s-ar putea sa nu fie folosit la potentialul sau maxim. Din cauza ca o metoda care foloseste params, poate sa fie apelata primind un vector, avem o oarecare compatibilitate cu varianta cand nu folosim keyword-ul params.
Prin folosirea acestui keyword, s-ar putea ca API pe care il expunem sa nu fie usor de inteles sau sa provoace o usoara dezorientare pentru dezvoltator, dar cred ca pot sa existe cazuri cand acesta sa ne simplice putin codul.
Pana acuma nu l-am folosit niciodata in productie, dar in viitor s-ar putea daca o sa gasesc cazuri cand chiar isi are rostul. In acelasi timp o sa am grija sa documentez codul destul de bine incat sa argumentez de ce l-am folosit si sa dau exemple de apeluri. Din cauza ca acest keyword nu este folosit si cunoscut in totalitate, poate sa provoace confuzie, iar acest lucru trebuie evitat.
Totusi parca exista un smell cand vrem sa introducem "params", aveti grija.

Voi l-ati folosit pana acuma? Credeti ca merita folosit?
Email ThisBlogThis!Share to XShare to FacebookShare to Pinterest
Posted in C# | No comments
Newer Post Older Post Home

0 comments:

Post a Comment

Subscribe to: Post Comments (Atom)

Popular Posts

  • Service Bus Topic - Automatic forward messages from a subscription to a topic
    Windows Azure Service Bus Topic is a service that enables us to distribute the same messages to different consumers without having to know e...
  • Patterns in Windows Azure Service Bus - Message Splitter Pattern
    In one of my post about Service Bus Topics from Windows Azure I told you that I will write about a post that describe how we can design an a...
  • CDN is not the only solution to improve the page speed - Reverse Caching Proxy
    I heard more and more often think like this: “If your website is to slow, you should use a CDN.” Great, CDN is THE solution for any kind of ...
  • E-Learning Vendors Attempt to Morph Mobile
    The sign should read: " Don't touch! Wet Paint !" I had a good chuckle today after receiving my latest emailed copy of the eLe...
  • Content Types - Level 6: Rich Media
    Level 6: Rich Media NOTE: This is part 7 of 7 and the conclusion of this continuing series; please see earlier posts for more background inf...
  • Publishing our CellCast Widget for iPad
    The rush has been on this week as our development team worked to design a new version of our CellCast Widget specifically for Apple's up...
  • Content Types - Level 5: Courseware
    Level 5: Content and Courseware NOTE: This is part 6 of 7 in a continuing series; please see earlier posts for more background information. ...
  • SQL - UNION and UNION ALL
    I think that all of us used until now UNION in a SQLstatement. Using this operator we can combine the result of 2 queries. For example we wa...
  • Cum sa salvezi un stream direct intr-un fisier
    Cred ca este a 2-a oara când întâlnesc aceasta cerința in decurs de câteva săptămâni. Se da un stream și o locație unde trebuie salvat, se c...
  • Content Types - Level 4: Reference
    Level 4: Reference Materials & Static Content NOTE: This is part 5 of 7 in a continuing series; please see earlier posts for more backgr...

Categories

  • .NET
  • .NET nice to have
  • #if DEBUG
  • 15 iunie 2011
  • 15 octombrie 2011
  • 2011
  • abstracta
  • action
  • adaugare
  • ajax
  • Amsterdam
  • Android
  • aplicatii
  • App Fabric
  • Apple iSlate
  • array
  • as
  • ASP.NET
  • AsReadOnly
  • Assembly comun
  • async
  • Asynchronous programming
  • asyncron
  • Autofac
  • AutoMapper
  • az
  • Azure
  • Azure AppFabric Cache
  • Azure backup solution
  • Azure Storage Explorer
  • azure. cloud
  • backup
  • BCP utility
  • bing maps v7
  • BitArray
  • BlackBerry
  • blob
  • BlobContainerPublicAccessType
  • breakpoint
  • bucuresti
  • C#
  • cache
  • CallerMemberName
  • CellCast
  • Certificate
  • CES
  • change
  • ChannelFactory
  • clasa
  • classinitialize
  • clean code
  • click event
  • close
  • Cloud
  • Cluj
  • cluj-napoca
  • Code contracts
  • code retrat
  • codecamp
  • CollectionAssert
  • Compact Edition
  • compara
  • Comparer T .Default
  • CompareTo
  • comparison
  • comunitate
  • concurs
  • Conditional attribute
  • configurare
  • connection string
  • container
  • content type
  • control
  • Convert
  • convertAll
  • convertor
  • cross platform
  • CRUD
  • css
  • custom properties
  • custom request
  • DACPAC
  • Daniel Andres
  • data sync service
  • database
  • date time
  • datetime
  • debug
  • default
  • delegate
  • dependency injection
  • deploy
  • DeploymentItem
  • design patterns
  • Dev de Amsterdam
  • development stoage
  • dictionary
  • diferente
  • digging
  • director
  • Directory.Exist
  • disable
  • dispatcher
  • dispose
  • dropdown
  • dynamic
  • EF
  • email
  • encoding
  • entity framework
  • enum
  • enumerable
  • Environment.NewLine
  • error
  • error 404
  • error handling
  • eveniment
  • event
  • ews
  • excel
  • exception
  • exchange
  • exita
  • explicit
  • export
  • extension
  • field
  • File.Exist
  • finalize
  • fire and forget
  • Fluent interface pattern
  • format
  • func
  • GC.SuppressFinalize
  • generic
  • getdirectoryname
  • globalization
  • gmail
  • hackathon
  • Hadoop
  • handle
  • HTML
  • html 5
  • Html.ActionLink
  • http://www.blogger.com/img/blank.gif
  • HttpModule
  • IComparable
  • IE
  • ienumerable
  • IIS
  • image
  • implicit
  • import
  • int
  • internationalization
  • Internet Explorer
  • interop
  • Ioc
  • IP Filter
  • iPhone
  • iQuest
  • IStructuralEquatable
  • ITCamp
  • itspark
  • java script
  • javascript
  • July 2012
  • KeyedByTypeCollection
  • KeyNotFoundException
  • Kinect SDK
  • lambda expression
  • LightSwitch Microsoft Silverlight
  • linq
  • list
  • lista
  • lista servicii
  • liste
  • Live Connect
  • Live ID
  • load
  • localization
  • lock
  • m-learning
  • MAC
  • Mango
  • map
  • mapare
  • mapare propietati
  • messagequeue
  • meta properties
  • method
  • MethodImpl
  • Metro App
  • Microsoft
  • Microsoft Sync Framework
  • mlearning
  • mlearning devices
  • Mobile Apps
  • mobile in the cloud
  • mobile learning
  • mobile services
  • Mobile Web
  • mongoDb
  • monitorizare
  • msmq
  • multitasking
  • MVC
  • MVC 3
  • MVVM
  • namespace
  • nextpartitionkey
  • nextrowkey
  • Ninject
  • nivel acces
  • no result
  • normalize
  • nosql
  • null expcetion
  • null object pattern
  • NullReferenceException
  • OAuth API
  • office
  • offline
  • Open ID
  • openhackeu2011
  • operations
  • operator
  • optimization
  • option
  • outputcache
  • OutputCacheProvider
  • override
  • paginare
  • pagination
  • path
  • persistare
  • Portable Library tool
  • Post event – CodeCamp Cluj-Napoca
  • predicate
  • predictions
  • prezentare
  • process
  • proiect
  • property
  • propietati
  • query
  • ReadOnlyCollection
  • ReadOnlyDictionary
  • referinta
  • reflection
  • remote
  • reply command
  • request
  • request response
  • resouce
  • REST
  • REST Client
  • RESTSharp
  • ronua
  • rss
  • rulare
  • salvare in fisier
  • sc
  • schimbare timp
  • select
  • select nodes
  • send
  • serializare
  • serialization
  • Server.Transfer. Resposen.Redirect
  • service bus
  • ServiceBase
  • servicecontroller
  • sesiune
  • session
  • Session_End
  • Session_Start
  • setup
  • Sibiu
  • signalR
  • Silverlight
  • sincronizare
  • Single Responsibility Principle
  • SkyDrive
  • skype
  • smartphones
  • smtp
  • Snapguide
  • sniffer
  • socket
  • solid
  • spec#
  • sql
  • Sql Azure
  • SQL CE
  • sql server 2008 RC
  • SRP
  • startuptype
  • stateful
  • stateless
  • static
  • stergere
  • store
  • store procedure
  • stream
  • string
  • string.join
  • struct
  • StructuralEqualityComparer
  • submit
  • switch
  • Symbian
  • Synchronized
  • system
  • tabele
  • table
  • techEd 2012
  • tempdata
  • test
  • testcleanup
  • testinitialize
  • testmethod
  • thread
  • timer
  • ToLower
  • tool
  • tostring
  • Total Cost Calculator
  • trace ASP.NET
  • transcoding
  • tuplu
  • tutorial
  • TWmLearning
  • type
  • unit test
  • unittest
  • UrlParameter.Optional
  • Validate
  • validation
  • verificare
  • video
  • view
  • ViewBag
  • virtual
  • visual studio
  • VM role
  • Vunvulea Radu
  • wallpaper
  • WCF
  • WebBrower
  • WebRequest
  • where clause
  • Windows
  • windows 8
  • Windows Azure
  • Windows Azure Service Management CmdLets
  • windows live messenger
  • Windows Mobile
  • Windows Phone
  • windows service
  • windows store application
  • Windows Task
  • WinRT
  • word
  • workaround
  • XBox
  • xml
  • xmlns
  • XNA
  • xpath
  • YMesseger
  • Yonder
  • Zip

Blog Archive

  • ►  2013 (139)
    • ►  November (17)
    • ►  October (12)
    • ►  September (10)
    • ►  August (7)
    • ►  July (8)
    • ►  June (15)
    • ►  May (12)
    • ►  April (17)
    • ►  March (16)
    • ►  February (9)
    • ►  January (16)
  • ▼  2012 (251)
    • ►  December (9)
    • ►  November (19)
    • ►  October (26)
    • ►  September (13)
    • ►  August (35)
    • ►  July (28)
    • ►  June (27)
    • ▼  May (24)
      • Post event - ITCamp 2012
      • Trail Ride to Float Mobile Learning Symposium
      • Windows 8: Error on video playing
      • Windows 8 for tables and viruses
      • Metro UI and Windows Metro Style Application is no...
      • Use lock in a block that contains a call to an asy...
      • DataContractSerializer and list of abstract class
      • The secret behind "params" keyword
      • Code Retreat Cluj-Napoca - 19/05/2012
      • InitializeComponent CLR error in Windows 8 Metro a...
      • Custom button image of AppBar in a Windows 8 Metro...
      • Get current position in Metro app on Windows 8 freeze
      • Azure - How to add custom settings to a Windows Az...
      • What are the base async patterns in .NET world
      • What does Task.Result really do
      • Performance Counter Setup on Windows Azure
      • How to change version of our solution assemblies
      • Use LINQ to get items of specific type
      • IT Camp 2012 - Cluj Napoca, 28,29 mai
      • How to deploy and debug remote on a Windows 8 tabl...
      • Windows Azure Instance - Remote Access Problems
      • Visual Studio 2011 BETA - XAML error report problems
      • How to get a valid daylight saving time - Part 2
      • How to get a valid daylight saving time
    • ►  April (18)
    • ►  March (17)
    • ►  February (20)
    • ►  January (15)
  • ►  2011 (127)
    • ►  December (11)
    • ►  November (20)
    • ►  October (8)
    • ►  September (8)
    • ►  August (8)
    • ►  July (10)
    • ►  June (5)
    • ►  May (8)
    • ►  April (9)
    • ►  March (14)
    • ►  February (20)
    • ►  January (6)
  • ►  2010 (26)
    • ►  December (1)
    • ►  November (1)
    • ►  October (1)
    • ►  June (2)
    • ►  May (1)
    • ►  April (4)
    • ►  March (1)
    • ►  February (1)
    • ►  January (14)
Powered by Blogger.

About Me

Unknown
View my complete profile