Linq to return ALL pairs of elements from two lists?

Question

Given lists l1 = {1, 2} and l2 = {4, 5, 6 } I want to get a new list that has elements:

rez = { {1, 4}, {1, 5}, {1, 6}, {2, 4}, {2, 5}, {2, 6} }

Suggestions?

Answer 1

Eric Lippert's already done it for you!

http://blogs.msdn.com/b/ericlippert/archive/2010/06/28/computing-a-cartesian-product-with-linq.aspx

Answer 2

Yes it is possible. Eric Lippert wrote a very good article on this topic:

Computing a Cartesian Product with LINQ

If you only have 2 lists, then you could directly use multiple from like this:

from a in s1 
from b in s2 
select new [] { a, b};

or even:

s1.SelectMany(a => s2.Select(b => new [] { a, b }));

But the solution given by Eric Lippert in the previous article allows you to compute the cartesian product of several sequences. With the following extension method:

public static IEnumerable<IEnumerable<T>> CartesianProduct<T>(this IEnumerable<IEnumerable<T>> sequences)
{
    IEnumerable<IEnumerable<T>> emptyProduct = new[] { Enumerable.Empty<T>() };
    return sequences.Aggregate(
        emptyProduct,
        (accumulator, sequence) =>
        from accseq in accumulator
        from item in sequence
        select accseq.Concat(new[] { item }));
}

You could write:

var l1 = new[] {1, 2};
var l2 = new[] {4, 5, 6};
var l3 = new[] {7, 3};

foreach (var result in new []{l1,l2,l3}.CartesianProduct())
{
    Console.WriteLine("{"+string.Join(",",result)+"}");
}

And obtain:

{1,4,7}
{1,4,3}
{1,5,7}
{1,5,3}
{1,6,7}
{1,6,3}
{2,4,7}
{2,4,3}
{2,5,7}
{2,5,3}
{2,6,7}
{2,6,3}

Answer 3

You want

l1.Join(l2, a => 1, b => 1, (a, b) => new [] { a, b });

Answer 4

var result = from a in l1
             from b in l2
             select new[] { a, b }

Answer 5

Here you go;

var rez =  from first in l1 
           from second in l2 
           select new[] { first, second };

Answer 6

Great article by Eric Lippert - see links in other answers. What's even better, this was the first try I did before looking at the answers on this page :)

In short:

var rez = 
    from e1 in l1
    from e2 in l2 
    select new {e1, e2};

Answer 7

Hi there, something like this will do what you are looking for.

var l1 = new List<int>{1,2};
var l2 = new List<int>{4,5,6};

var p = from n in l1
        from m in l2
        select new { Fst = n, Scd = m };

with this answer your tuples {x,y} are an anonymous type.