Question

I have a List<List>. I want to get a single List from that.

List<int> from List<List<SomeClass>()

For loop is an obvious solution but i want something more better and eligent from performance point of view.

List<List<Employee>> ValueLists;

List<int> Current= ValueLists.SelectMany(u=>u.Select(v=>v.EmployeeID));

Answer 1

Try this:

var list = listOfLists.SelectMany(x => x).ToList();

---

I’m not sure exactly what extra info you’re after. The edit you made to the question is almost complete code.

You should have written:

List<int> Current =
    ValueLists
        .SelectMany(u => u.Select(v => v.EmployeeID))
        .ToList();

This could be written as this instead:

var query =
    from u in ValueLists
    from v in u
    select v.EmployeeID;

List<int> Current = query.ToList();

Maybe that gives more clarity.