C#•13mo ago

✅ What's the difference between Public and Private? and why would someone use it?

9 Replies

in a class, public allows code written outside of the class definition to access whatever you declared public like a method or property and private does not it's useful to hide the inner workings of a class from outside code so you have more control over when and how it can be used

Yazed0071OP•13mo ago

from a user or for you to avoid bugs?

Jimmacle•13mo ago

both code is easier to debug if the ways it can be accessed/modified are limited as an example, say you have a Person class with an Age property and you want to be able to make them older sure, you could make Age public but that allows other code to set any age they want, even an invalid one like a negative number instead you'd want to control their access like

public int Age { get; private set; }
public void MakeOlder(int years)
{
  if (years < 0) throw new ArgumentOutOfRangeException();
  Age += years;
}

public int Age { get; private set; }
public void MakeOlder(int years)
{
  if (years < 0) throw new ArgumentOutOfRangeException();
  Age += years;
}

this way age can only be modified in a way that the Person class has control over to make sure other code can't put it in a bad state

Yazed0071OP•13mo ago

what does ?

{ get; private set;}

{ get; private set;}

Jimmacle•13mo ago

it means that other code can read the value of Age but can't change it, only code inside the Person class can

var x = person.Age; // ok
person.Age = 1000; // error

var x = person.Age; // ok
person.Age = 1000; // error

Yazed0071OP•13mo ago

public : can read and change the value private : can't read nor change public with { get; private set; } at the end : read but not change?

Jimmacle•13mo ago

right, properties allow you to control the accessibility of getting and setting the value independently you could also have { private get; set; } or any other combination of access modifiers so in this case we don't want other code to set any age they want, so we make the setter private and create a method to modify age in an acceptable way

Yazed0071OP•13mo ago

I see, thank you so much!

Accord•13mo 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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✅ What's the difference between Public and Private? and why would someone use it?