C#•2y ago

✅ Understanding virtual keyword

Hi, I am familiar with inheritance and polymorphism but I struggle to understand the benefit of the virtual keyword. The idea behind the virtual keyword is to be able to provide a default implementation but also being able to possibly override that implementation in inheriting types. But we can do the exact same thing with just regular methods, so does virtual only exist to express clearer intend that methods shall be reimplemented in inheriting types by other developers or what is the purpose of that keyword?

10 Replies

Thinker•2y ago

But we can do the exact same thing with just regular methods

Well, no you can't You can't override non-virtual/abstract methods.

Florian VoßOP•2y ago

or hide with new then, my bad still same question tho

Thinker•2y ago

hiding is not the same thing as overriding

Florian VoßOP•2y ago

whats the difference?

Jaiganésh•2y ago

If you have a reference to the base class, it will call the base class method with hiding in derived class. While with virtual, it will always call the most derived method.

Florian VoßOP•2y ago

oh wow I didn't know that I thought it would always use the most derived method

Jaiganésh•2y ago

That's when it's virtual.

MODiX•2y ago

thinker227#5176

REPL Result: Success

class A
{
    public void F() => Console.WriteLine("a");
}

class B : A
{
    // hide
    public new void F() => Console.WriteLine("b");
}

class C
{
    public virtual void F() => Console.WriteLine("c");
}

class D : C
{
    // override
    public override void F() => Console.WriteLine("d");
}

A a = new B();
a.F();

C c = new D();
c.F();

class A
{
    public void F() => Console.WriteLine("a");
}

class B : A
{
    // hide
    public new void F() => Console.WriteLine("b");
}

class C
{
    public virtual void F() => Console.WriteLine("c");
}

class D : C
{
    // override
    public override void F() => Console.WriteLine("d");
}

A a = new B();
a.F();

C c = new D();
c.F();

Console Output

a
d

a
d

Compile: 705.157ms | Execution: 53.724ms | React with ❌ to remove this embed.

Florian VoßOP•2y ago

understood, thank you both very much

Thinker•2y ago

Gaming

Programming

✅ Understanding virtual keyword