public void Test()
        {
            var displayClass = new DisplayClass();
            displayClass.numberToAdd = 1;
            displayClass.numberToSubstract = 2;

            var listToProcess =new List<int>();
            ProcessList(listToProcess, displayClass.addition, displayClass.substraction);
        }

        private sealed class DisplayClass
        {
            public int numberToAdd;
            public int numberToSubstract;

            public int addition(int x)
            {
                return x + numberToAdd;
            }

            public int substraction(int x)
            {
                return x - numberToSubstract;
            }
        }