C#•9mo ago

❔ ✅ why properties instead of public fields

in this case

class Person
{
  public int age;
  //vs
  public int Age {get; set;}
}

class Person
{
  public int age;
  //vs
  public int Age {get; set;}
}

36 Replies

Thinker•9mo ago

You can change the implementation of a property, but you can't with a field. eg. a property allows you to in the future change what the property does, you might want some validation in the setter or that the getter does something different

Jimmacle•9mo ago

also, properties give you more options for accessibility control like being able to read a value but not set it

fæ•9mo ago

readonly fields?

Jimmacle•9mo ago

let me be more specific: read a field but not set it outside of the class like public int Age { get; private set; }

fæ•9mo ago

im asking if readonly fields are the same thing

Jimmacle•9mo ago

they are not

fæ•9mo ago

why

Jimmacle•9mo ago

readonly fields can only be set once, in the constructor

fæ•9mo ago

and this can be set anywhere inside the class

Jimmacle•9mo ago

a property with a private setter can be updated as many times as you want, but only from code inside the class it's defined in

fæ•9mo ago

but not outside of it?

Jimmacle•9mo ago

right the equivalent of a readonly field as a property is a property with just a getter, like public int Age { get; }

fæ•9mo ago

can i suggest an example and you tell me if its a good way to use a get-only property vs readonly? let me write it out and tell me if its a good usecase

Jimmacle•9mo ago

my rule is anything that is exposed outside the class should be a property, with the exception of constants (literally const)

fæ•9mo ago

public int incrementMe { get => incrementMe++ }

public int incrementMe { get => incrementMe++ }

everytime this is accessed will it increment?

Jimmacle•9mo ago

you don't want getters to change state, that's unexpected behavior also, that's infinitely recursive

fæ•9mo ago

what if that's my intention? minus the recursiveness

Jimmacle•9mo ago

i would suggest making it a method like GetNextValue()

fæ•9mo ago

what if i want to read how many times a property was accessed

Jimmacle•9mo ago

that would be acceptable i guess

fæ•9mo ago

okay i think i get it and this cant be achieved with a field alone

Jimmacle•9mo ago

just consider code like

var a = x.incrementMe;
var b = x.incrementMe;

var a = x.incrementMe;
var b = x.incrementMe;

if someone is coming across that for the first time what would they expect?

fæ•9mo ago

that a == b

Jimmacle•9mo ago

right, so you want to avoid writing code that would break that expectation

fæ•9mo ago

i see that isn't ideal but i could change the state of another field right?

Jimmacle•9mo ago

sure

fæ•9mo ago

or can properties only interfere with their own backing fields

Jimmacle•9mo ago

properties can do pretty much anything, they are essentially pairs of methods (they literally compile down to get and set methods)

fæ•9mo ago

what would be the difference between const and readonly then why would a const not need a property (unless i misunderstood)

Jimmacle•9mo ago

const is a value that is defined at compile time readonly can be initialized to a value at runtime but can't be changed after that

fæ•9mo ago

i thought .net was always JIT i think i might be confusing things C# doesnt work like java where it's interpreted by the jvm, right? the CLR works differently?

Thinker•9mo ago

C# is compiled to IL which is then JITed It works exactly like Java IL is like JAR and the CLR is like the JVM

fæ•9mo ago

then java isnt interpreted either sorry about that okay i understand now. i'm gonna set this to resolved. thank you jimmacle and thinker is there a way to close/tag this as resolved

Jimmacle•9mo ago

$close

MODiX•9mo ago

Use the /close command to mark a forum thread as answered

Accord•9mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ ✅ why properties instead of public fields