Property in C# is a member of a class that provides a flexible mechanism for classes to expose private fields. Internally, C# properties are ...
PropertiesInC#
RajeshVS
UpdateddateOct21,2020
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LearnhowtousepropertiesinC#.
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PropertyinC#isamemberofaclassthatprovidesaflexiblemechanismforclassestoexposeprivatefields.Internally,C#propertiesarespecialmethodscalledaccessors.AC#propertyhavetwoaccessors,getpropertyaccessorandsetpropertyaccessor.Agetaccessorreturnsapropertyvalue,andasetaccessorassignsanewvalue.Thevaluekeywordrepresentsthevalueofaproperty.
PropertiesinC#and.NEThavevariousaccesslevelsthatisdefinedbyanaccessmodifier.Propertiescanberead-write,read-only,orwrite-only.Theread-writepropertyimplementsboth,agetandasetaccessor.Awrite-onlypropertyimplementsasetaccessor,butnogetaccessor.Aread-onlypropertyimplementsagetaccessor,butnosetaccessor.
InC#,propertiesarenothingbutanaturalextensionofdatafields.Theyareusuallyknownas'smartfields'inC#community.Weknowthatdataencapsulationandhidingarethetwofundamentalcharacteristicsofanyobjectorientedprogramminglanguage.InC#,dataencapsulationispossiblethrougheitherclassesorstructures.Byusingvariousaccessmodifierslikeprivate,public,protected,internaletcitispossibletocontroltheaccessibilityoftheclassmembers.
Usually,insideaclass,wedeclareadatafieldasprivateandwillprovideasetofpublicSETandGETmethodstoaccessthedatafields.Thisisagoodprogrammingpracticesincethedatafieldsarenotdirectlyaccessibleoutsidetheclass.Wemustusetheset/getmethodstoaccessthedatafields.
Anexample,whichusesasetofset/getmethods,isshownbelow.
//SET/GET methods //Author: [email protected] using System; class MyClass { private int x; public void SetX(int i) { x = i; } public int GetX() { return x; } } class MyClient { public static void Main() { MyClass mc = new MyClass(); mc.SetX(10); int xVal = mc.GetX(); Console.WriteLine(xVal); } }
Theoutputfromabovelistingisshownbelow.
ButC#providesabuiltinmechanismcalledpropertiestodotheabove.InC#,propertiesaredefinedusingthepropertydeclarationsyntax.Thegeneralformofdeclaringapropertyisasfollows.
{ get { } set { } }
Wherecanbeprivate,public,protectedorinternal.ThecanbeanyvalidC#type.Notethatthefirstpartofthesyntaxlooksquitesimilartoafielddeclarationandsecondpartconsistsofagetaccessorandasetaccessor.
Forexample,theaboveprogramcanbemodifiedwithapropertyXasfollows.
class MyClass { private int x; public int X { get { return x; } set { x = value; } } }
TheobjectoftheclassMyClasscanaccessthepropertyXasfollows.
MyClass mc = new MyClass();
mc.X=10;//callssetaccessorofthepropertyX,andpass10asvalueofthestandardfield'value'.
Thisisusedforsettingvalueforthedatamemberx.
Console.WriteLine(mc.X);//displays10.CallsthegetaccessorofthepropertyX.
Thecompleteprogramisshownbelow.
//C#: Property //Author: [email protected] using System; class MyClass { private int x; public int X { get { return x; } set { x = value; } } } class MyClient { public static void Main() { MyClass mc = new MyClass(); mc.X = 10; int xVal = mc.X; Console.WriteLine(xVal);//Displays 10 } }
Rememberthatapropertyshouldhaveatleastoneaccessor,eithersetorget.Thesetaccessorhasafreevariableavailableinitcalledvalue,whichgetscreatedautomaticallybythecompiler.Wecan'tdeclareanyvariablewiththenamevalueinsidethesetaccessor.
Wecandoverycomplicatedcalculationsinsidethesetorgetaccessor.Eventheycanthrowexceptions.
Sincenormaldatafieldsandpropertiesarestoredinthesamememoryspace,inC#,itisnotpossibletodeclareafieldandpropertywiththesamename.
StaticProperties
C#alsosupportsstaticproperties,whichbelongstotheclassratherthantotheobjectsoftheclass.Alltherulesapplicabletoastaticmemberareapplicabletostaticpropertiesalso.
Thefollowingprogramshowsaclasswithastaticproperty.
//C# : static Property //Author: [email protected] using System; class MyClass { private static int x; public static int X { get { return x; } set { x = value; } } } class MyClient { public static void Main() { MyClass.X = 10; int xVal = MyClass.X; Console.WriteLine(xVal);//Displays 10 } }
Rememberthatset/getaccessorofstaticpropertycanaccessonlyotherstaticmembersoftheclass.Also,staticpropertiesareinvokingbyusingtheclassname.
Properties&Inheritance
ThepropertiesofaBaseclasscanbeinheritedtoaDerivedclass.
//C# : Property : Inheritance //Author: [email protected] using System; class Base { public int X { get { Console.Write("Base GET"); return 10; } set { Console.Write("Base SET"); } } } class Derived : Base { } class MyClient { public static void Main() { Derived d1 = new Derived(); d1.X = 10; Console.WriteLine(d1.X); } }
Theoutputfromabovelistingisshownbelow.
Theaboveprogramisverystraightforward.Theinheritanceofpropertiesisjustlikeinheritanceanyothermember.
Properties&Polymorphism
ABaseclasspropertycanbepolymorphicallyoverriddeninaDerivedclass.Butrememberthatthemodifierslikevirtual,overrideetcareusingatpropertylevel,notataccessorlevel.
//C# : Property : Polymorphism //Author: [email protected] using System; class Base { public virtual int X { get { Console.Write("Base GET"); return 10; } set { Console.Write("Base SET"); } } } class Derived : Base { public override int X { get { Console.Write("Derived GET"); return 10; } set { Console.Write("Derived SET"); } } } class MyClient { public static void Main() { Base b1 = new Derived(); b1.X = 10; Console.WriteLine(b1.X); } }
Theoutputfromabovelistingisshownbelow.
AbstractProperties
Apropertyinsideaclasscanbedeclaredasabstractbyusingthekeywordabstract.Rememberthatanabstractpropertyinaclasscarriesnocodeatall.Theget/setaccessorsaresimplyrepresentedwithasemicolon.Inthederivedclasswemustimplementbothsetandgetassessors.
Iftheabstractclasscontainsonlysetaccessor,wecanimplementonlysetinthederivedclass.
Thefollowingprogramshowsanabstractpropertyinaction.
//C# : Property : Abstract //Author: [email protected] using System; abstract class Abstract { public abstract int X { get; set; } } class Concrete : Abstract { public override int X { get { Console.Write(" GET"); return 10; } set { Console.Write(" SET"); } } } class MyClient { public static void Main() { Concrete c1 = new Concrete(); c1.X = 10; Console.WriteLine(c1.X); } }
Theoutputfromabovelistingisshownbelow.
ThepropertiesareimportantfeaturesaddedinlanguagelevelinsideC#.TheyareveryusefulinGUIprogramming.RememberthatthecompileractuallygeneratestheappropriategetterandsettermethodswhenitparsestheC#propertysyntax.
PropertiesAccessModifiers
Accessmodifiersdefinestheaccesslevelofapropertywhetherapropertycanbeaccessedbyanycallerprogram,withinanassembly,orjustwithinaclass.
Thefollowingtabledescribesaccesslevelmodifiers.
public-Thetypeormembercanbeaccessedbyanyothercodeinthesameassemblyoranotherassemblythatreferencesit.Private-Thetypeormembercanbeaccessedonlybycodeinthesameclassorstruct.protected-Thetypeormembercanbeaccessedonlybycodeinthesameclass,orinaclassthatisderivedfromthatclass.internal-Thetypeormembercanbeaccessedbyanycodeinthesameassembly,butnotfromanotherassembly.protectedinternal-Thetypeormembercanbeaccessedbyanycodeintheassemblyinwhichitisdeclared,orfromwithinaderivedclassinanotherassembly.privateprotected-Thetypeormembercanbeaccessedonlywithinitsdeclaringassembly,bycodeinthesameclassorinatypethatisderivedfromthatclass.
AutomaticallyImplementedProperties
AtypicalimplementationofapublicpropertylookslikeListing.Thedefaultimplementationofapropertyneedsagetterandsetter.
private string name; public string Name { get { return this.name; } set { this.name = value; } }
Auto-implementedpropertiesinC#makescodemorereadableandcleanifthereisnoadditionalcalculationneeded.TheabovecodeofListingcanbereplacedbythefollowingonelineofcodeinListing
public string Name { get; set; }
Incaseofauto-implementedproperties,thecompilercreatesaprivatefieldvariablethatcanonlybeaccessedthroughtheproperty'sgetterandsetter.
CodelistedinListingisaclasswithseveralauto-initializedproperties.
using System; class Author { // Read-write properties public string Name { get; set; } public string Publisher { get; set; } public string Book { get; set; } public Int16 Year { get; set; } public double Price { get; set; } public string PriceInString { get { return string.Format("${0}", Price); } } // Read-only properties public string Names { get; } // Initialization of a property public double AuthorCount { get; private set; } = 99; // Class constructor public Author(string name, string publisher, string book, Int16 year, double price) { Name = name; Publisher = publisher; Book = book; Year = year; Price = price; } // Public methods public string AuthorDetails() { return string.Format("{0} is an author of {1} published by {2} in year {3}. Price: ${4}", Name, Book, Publisher, Year, Price); } public double CostOfThousandBooks() { if (Price > 0) return Price * 1000; return 0; } }
ThecodeinListingiscreatesaninstanceoftheclassandcallsitsmethodsandproperties.
class Program { static void Main() { Author author = new Author("Mahesh Chand", "Apress", "Programming C#", 2003, 49.95); Console.WriteLine(author.AuthorDetails()); Console.WriteLine("Author published his book in {0}", author.Year); author.Price = 50; Console.WriteLine(author.CostOfThousandBooks().ToString()); Console.ReadKey(); } }
AbstractPropertiesC#propertiesPropertiesinC#StaticProperties
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