public void Test()
        {
            var numberToBeAdded = 4;
            var listToProcess = new List<int>();
            ProcessList(listToProcess, x=> x + numberToBeAdded);
        }

        private void ProcessList(List<int> listToProcess, Func<int,int> processingFunction)
        {
            for (int index = 0; index < listToProcess.Count; index++)
            {
                var item = listToProcess[index];
                item = processingFunction(item);
            }
        }