Question

I want to add two lists of a numeric type such that
addedList[x] = listOne[x] + listTwo[x]

The output of the list needs to be a Generic.IEnumerable that I can use in future linq queries.

While I was able to do it using the code below, I can’t help but feel like there must be a better way. Any ideas?

List<int> firstList = new List<int>(new int[] { 1, 3, 4, 2, 5, 7, 2, 5, 7, 8, 9, 0 });
List<int> secondList = new List<int>(new int[] { 4, 6, 8, 3, 1, 5, 9, 3, 0 });

int findex = 0;

ILookup<int, int> flookup = firstList.ToLookup(f =>
                            {
                               int i = findex;
                               findex++; 
                               return i;
                               }, p => p);  

var listsAdded = from grp in flookup
                 select grp.First() + secondList.ElementAtOrDefault(grp.Key);

foreach (int i in listsAdded)
  Console.WriteLine(i);

Answer 1

var result = 
   from i in 
        Enumerable.Range(0, Math.Max(firstList.Count, secondList.Count))
   select firstList.ElementAtOrDefault(i) + secondList.ElementAtOrDefault(i);