Question

At the moment I use List<int> ints = tuple.Item2.Select(s => s.Value).ToList() but this looks inefficient when tuple.Item2 has 1000’s of items. Any better way to achieve this? except using a for loop.

Answer 1

The built-in way to convert each element in one List<T1> and store the result in another List<T2> is List<T1>.ConvertAll.

List<int> ints = tuple.Item2.ConvertAll(s => s.Value);

Unlike .Select(...).ToList() or .Cast(...).ToList(), this method knows the list size in advance, and prevents unnecessary reallocations that .ToList() cannot avoid.

For this to work, tuple.Item2 must really be a List<int?>. It’s not an extension method, it cannot work on the generic IEnumerable<int?> interface.