🔐 Access Modifiers in C#: public, private, protected, internal & More Explained

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Published on: June 7, 2025

Category: C# Basics

Tags: CSharp, Access Modifiers, Encapsulation, OOP, Interview Questions, public private protected internal, .NET Dev Corner, Class Design, .NET Fundamentals

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✨ Introduction

Access modifiers are essential in C# for controlling how members of a class (variables, methods, constructors, etc.) are exposed to other parts of your code. They are the cornerstone of encapsulation, one of the pillars of object-oriented programming.

🔓 1. public

• Access Level: Accessible from anywhere in the project or external assemblies.
• Use When: You want complete access to a method or class member.

public class Car
{
    public string Brand;
    public void Start() => Console.WriteLine("Engine started");
}

🧠 Think of public as a highway — anyone can drive through.

🔒 2. private

• Access Level: Accessible only within the containing class.
• Use When: You want to encapsulate internal logic or variables.

public class BankAccount
{
    private decimal balance = 0;
    public void Deposit(decimal amount) => balance += amount;
}

🧠 private protects your internal data from accidental misuse.

🛡️ 3. protected

• Access Level: Accessible within the containing class and its subclasses (even in other assemblies).
• Use When: You’re building a base class meant to be extended.

public class Animal
{
    protected void Breathe() => Console.WriteLine("Breathing...");
}
public class Dog : Animal
{
    public void Act() => Breathe();
}

🧠 protected is like family access — inherited members get to use it.

🏠 4. internal

• Access Level: Accessible only within the same assembly (project).
• Use When: You want to hide members from other assemblies but expose them within yours.

internal class FileHelper
{
    internal void CleanTempFiles() { }
}

🧠 Think of internal as company access — shared within the same project only.

🧬 5. protected internal

• Access Level: Accessible within the same assembly or from derived classes in other assemblies.

public class Logger
{
    protected internal void Log(string message) => Console.WriteLine(message);
}

🧬 6. private protected (C# 7.2+)

• Access Level: Accessible within the same assembly and only in derived classes.

public class Settings
{
    private protected void Load() => Console.WriteLine("Loading settings");
}

🔍 Comparison Table

Modifier	Same Class	Derived Class	Same Assembly	External Assembly
public	✅	✅	✅	✅
private	✅	❌	❌	❌
protected	✅	✅	❌	✅ (if inherited)
internal	✅	✅	✅	❌
protected internal	✅	✅	✅	✅ (if inherited)
private protected	✅	✅	✅	❌

🎯 When to Use Which Modifier?

Expose to all projects	public
Hide implementation details	private
Share with child classes only	protected
Share within the same assembly	internal
Advanced hybrid control	protected internal, private protected

💡 Interview Tip

Expect to be asked:

• “What’s the difference between internal and protected internal?”
• “How do you apply encapsulation in C#?”

📌 Final Thoughts

Access modifiers define how your code communicates internally and externally. Choose wisely for cleaner, scalable design.

🔐 Encapsulation starts with proper access control.

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📬 Stay Connected

• 🔗 Blog: www.ajaygangwar.com
• 💼 LinkedIn: Ajay Gangwar
• 📧 Email: seajaygangwar@gmail.com

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