score:173

A cross-join is simply the Cartesian product of two sets. There's no explicit join operator for it.

```var combo = from p in people
from c in cars
select new
{
p.Name,
c.Make,
c.Model,
c.Colour
};
```

score:8

Extension Method:

``````public static IEnumerable<Tuple<T1, T2>> CrossJoin<T1, T2>(this IEnumerable<T1> sequence1, IEnumerable<T2> sequence2)
{
return sequence1.SelectMany(t1 => sequence2.Select(t2 => Tuple.Create(t1, t2)));
}
``````

And use like:

``````vals1.CrossJoin(vals2)
``````

score:13

A `Tuple` is a good type for Cartesian product:

``````public static IEnumerable<Tuple<T1, T2>> CrossJoin<T1, T2>(IEnumerable<T1> sequence1, IEnumerable<T2> sequence2)
{
return sequence1.SelectMany(t1 => sequence2.Select(t2 => Tuple.Create(t1, t2)));
}
``````

score:27

Based on Steve's answer, the simplest expression would be this:

``````var combo = from Person in people
from Car    in cars
select new {Person, Car};
``````

score:43

The same thing with the Linq extension method `SelectMany` (lambda syntax):

``````var names = new string[] { "Ana", "Raz", "John" };
var numbers = new int[] { 1, 2, 3 };
var newList=names.SelectMany(
x => numbers,
(y, z) => { return y + z + " test "; });
foreach (var item in newList)
{
Console.WriteLine(item);
}
``````