What is the difference between public, private, protected, and having no access modifier in C#?

In C#, access modifiers are like invisible guardians that control who can see and interact with different parts of your code. Think of them as security guards for your program.

Public

• What it is: Public is like shouting from the mountaintop! It means that anyone, anywhere in your code, can access the thing (like a variable or a method) with this modifier.
• Example:

  public class PublicExample
  {
      public int PublicVariable = 10;
  
      public void PublicMethod()
      {
          Console.WriteLine("This method is accessible by everyone!");
      }
  }
  

Private

• What it is: Private is like having a secret password to access something. Only the code inside the same class can use or see the thing with a private modifier.
• Example:

  public class PrivateExample
  {
      private int secretNumber = 42;
  
      private void PrivateMethod()
      {
          Console.WriteLine("This method is a secret!");
      }
  }
  

Protected

• What it is: Protected is like sharing with family. It allows the thing to be seen and used not only by its own class but also by any class that inherits from it.
• Example:

  public class BaseClass
  {
      protected int protectedVariable = 100;
  
      protected void ProtectedMethod()
      {
          Console.WriteLine("This method is accessible by family (inheritors)!");
      }
  }
  
  public class InheritedClass : BaseClass
  {
      public void UseProtectedMember()
      {
          Console.WriteLine($"Accessing protected variable: {protectedVariable}");
          ProtectedMethod();
      }
  }
  

No Access Modifier (Internal)

• What it is: When you don't specify any modifier, the default is like having a "Members Only" sign at the door. Only code within the same project (folder) can access the thing.
• Example:

  class InternalExample
  {
      internal string internalVariable = "Accessible within the same project";
  
      internal void InternalMethod()
      {
          Console.WriteLine("This method is for members only!");
      }
  }
  

Summary

• Public: Everyone can access.
• Private: Only the class itself can access.
• Protected: Accessible by the class and its "family" (inheritors).
• No Access Modifier (Internal): Only accessible within the same project.

Understanding these modifiers helps you control who can use and see the different parts of your code, creating a well-organized and secure program.