Adding parameter to instance of a class during runtime

So here I have a constructor from the class “Existence”.

	public Existence (string _name, int _dayborn, int _monthborn, int _yearborn)
		name = _name;
		dayborn = _dayborn;
		monthborn = _monthborn;
		yearborn = _yearborn;

so I’ll make an instance of the class using the constructor above

Existence player;

player = new Existence ("Charles", 1, 3, 1991);

I’ll be able to access and change those attributes if I want to during runtime.

But what if during Runtime I want to add an extra parameter to this instance? Like let’s say, Haircut…

How would I do this? Recreate the constructor and the instance? Please help

Filling this in as someone might find this helpful and as time passed no one answered.
You could use a pattern know as Decorator, it’s an intermediate pattern that allows you to do what you’re asking.
You can also take a peek in this example here.