just an example, you could pass your stack variable as an argument to the GetSum() function. 
private static int GetSum()
        {
              Stack<int> stack = new Stack<int>();
            stack.Push(2);
            stack.Push(5);
            stack.Push(7);
            stack.Push(4);
            stack.Push(1);
            int sum = 0;
            foreach (int number in stack)
            {
                if (number % 2 != 0)
                {
                    sum += number;
                }
            }
        return sum;
    }
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solved function to calculate the sum of odd numbers in a given stack [closed]