Polymorphism

Relax. We'll talk through this in plain words — no textbook voice.

Polymorphism means different objects can respond in their own way when you call a method with the same name on them. You mark the method virtual in the base class, and derived classes can override it.

csharp

class Animal
{
    public virtual void MakeSound()
    {
        Console.WriteLine("The animal makes a sound");
    }
}

class Dog : Animal
{
    public override void MakeSound()
    {
        Console.WriteLine("The dog says: woof");
    }
}

class Cat : Animal
{
    public override void MakeSound()
    {
        Console.WriteLine("The cat says: meow");
    }
}

class Program
{
    static void Main(string[] args)
    {
        Animal myDog = new Dog();
        Animal myCat = new Cat();

        myDog.MakeSound();
        myCat.MakeSound();
    }
}

What to watch out for

Animal myDog = new Dog(); holds it as the base type, but the method that actually runs is the override defined in Dog.
This concept is a lifesaver for patterns like plugin systems, payment providers, and notification channels.

You should see

The dog says: woof The cat says: meow