Merging multiple lists

Question

Given that there I have a list of lists, List<List<T>>, in which all lists contain 0 or more items, likely, but not necessarily all the same number. And I would like tho have a list containing all the items in the Lists... but I want the order to be as follows: first the first items off all the lists, in order that they appear in the 'super-list'.

Ex.

List[0] = { 'Apple', 'Blueberry', 'Cranberry' }
List[1] = { 'Anteater', 'Baboon', 'Camel', 'Dodo'}
List[2] = { 'Albatross', 'Blackbird', 'Chicken'}

result = { 'Apple', 'Anteater', 'Albatross', 'Blueberry', 'Baboon', 
           'Blackbird', 'Cranberry', 'Camel', 'Chicken', 'Dodo' }

(note that this is NOT alphabetical order, Blueberry comes before Baboon)

Ofcourse, i could just loop through the 'superlist' with a counter, adding items to the resultslist one by one, as long as there is a list that isn't empty:

int i = 0;
bool done = false;

while (!done)
{
    bool found = false;

    foreach (list l in superlist)
    {
        if (l.Count() > i)
        {
           found = true;
           result.Add(l[i]);
        }
    }

    i++;

    if (!found)
        done = true;
}

But it would be way nicer to use some optimized LINQ function to do this. I have been looking into Zip, GroupBy and Aggregate, but couldn't get them to work.

So: Is there a pretty LINQ function, or combination of multiple, that would turn this into pretty code, or should I stick by (and maybe optimize) my current function?

Edit: A simple SelectMany(x => x) also doesn't do the trick, as it preserves the order of the lists, instead of folding them, like my algorithm does. See my initial question for more details.

Answer 1

You need SelectMany

var result = lists.SelectMany(x => x.Select((s, inx) => new { s, inx }))
                .GroupBy(x => x.inx)
                .SelectMany(x => x.Select(y => y.s))
                .ToList();

---

EDIT

For those, who want to try, the initialization code.

List<List<string>> lists = new List<List<string>>()
        {
            new List<string>(){ "Apple", "Blueberry", "Cranberry" },
            new List<string>(){ "Anteater", "Baboon", "Camel", "Dodo"},
            new List<string>(){ "Albatross", "Blackbird", "Chicken"},
        };

EDIT 2

OUTPUT: Apple,Anteater,Albatross,Blueberry,Baboon,Blackbird,Cranberry,Camel,Chicken,Dodo

Answer 2

Just use MyListOfLists.SelectMany(x => x).OrderByDescending(x => x).ToList()

SelectMany will flatten your lists into one. OrderByDescending operates on that result and will put the results in alphabetical order (which I think you want). Then call ToList to force execution and get a List<string> instead of an IEnumerable<string>