virtual and override

[N0zzy]

I apologize for stupid questions. there is such an example with the result of a pie.
below are methods with "signature" virtual.
How can I change to "override" and is it possible?

[jakubmisek]

override is on overridden methods (https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/override).

You cannot "change" it to override. To define an overriden method, you have to override a virtual method:

class A {
  function foo() {/* do somethig */} // public virtual void foo()
}
class B extends A {
  function foo() {/* do something else */} // public override void foo()
}