c# if statement in constructor

class Calculation
    {
        // every time you use a comboBox you have to create a load event in order to populate it
        public static char[] actors = { '+', '-', '*', '/' };

        decimal x;
        decimal y;
        char actor;
        decimal result;

        public Calculation(decimal _x, decimal _y, char _actor)
        {
            x = _x;
            y = _y;
            actor = _actor;

            // if actor this then result = add() etc...
        }

        public override string ToString()
        {
            return String.Format("{0} {1} {2} = {3}", x, actor, y, result);
        }

        public decimal add()
        {
            return result = x + y;
        }

        public decimal subtract()
        {
            return result = x - y;
        }

        public decimal multiply()
        {
            return result = x * y;
        }

        public decimal divide()
        {
            return result = x / y;
        }
    }