internal vs protected in C#

However, the internal and protected modifiers are a bit more complicated.

• Use internal when you want to restrict access to only within the same assembly.
• Use protected when you want to limit access to the class itself and its subclasses.

In simpler terms, internal makes something "private" to the assembly, while protected makes it "private" to the class and its subclasses.

Key Differences:

• Access Scope:
  • internal: Accessible within the same assembly.
  • protected: Accessible within the class and its subclasses, even across different assemblies.
• Usage Context:
  • internal is ideal for limiting access within a single assembly or module.
  • protected is useful when you want to provide access to derived classes while keeping members hidden from external code.

For example:

// 'internal' example
public class Bird
{
    internal void Fly()
    {
        Console.WriteLine("Bird is flying.");
    }
}

// 'protected' example
public class Bird
{
    protected void Fly()
    {
        Console.WriteLine("Bird is flying.");
    }
}

public class Sparrow : Bird
{
    public void TestFly()
    {
        // Can access protected method in derived class
        Fly();
    }
}

In the internal example, the Fly() method is only accessible within the same assembly. In the protected example, Fly() is accessible in the Sparrow subclass, even though Sparrow could be in a different assembly.