Question

I want to do something like below:

total.ForEach(x => x = Math.Abs(x));

However x is not a reference value. How would I go about doing it?

Edit:

Is it possible to do this in place and not creating another list and not using a for loop?

Answer 1

You can use Linq.

total.Select(x => Math.Abs(x)).ToList();

That will give you a new list of the absolute values in total.
If you want to modify in place

for(int i = 0; i < total.Count; i++)
{
     total[i] = Math.Abs(total[i]);
}