You mean you want to call the base constructor from the derived constructor? Yes, you can do that with the base() construct.
public Derived(int sides)
: base(sides)
When Square() actually isn’t a constructor (it is in your question, no return type or void) but a method, you can do it like this:
public override returntype Foo(...)
{
// your adaptation
base.Foo(...)
The method in the base class has to be virtual for this to work.
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