Cartesianple

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class CartesianProductSelectManyExample
{
    public static void Main(string[] args)
    {
        var abcArray = new string[]{"a", "b", "c"};
        var xyzArray = new string[]{"x", "y", "z"};

        var combos = CartesianProductSmart(abcArray, xyzArray);

        foreach(var combo in combos)
        {
            Console.WriteLine(string.Format("[{0},{1}]", combo[0], combo[1]));
        }
    }

    private static string[][] CartesianProductSmart(string[] arr1, string[] arr2)
    {
        // for each s1 in arr1, extract arr2,
        // then pass s1 and s2 into a newly-made string array.
        return arr1.SelectMany(s1 => arr2, (s1, s2) => new string[]{s1, s2})
            .ToArray();
    }

    private static string[][] CartesianProductDumb(string[] arr1, string[] arr2)
    {
        // the dumb way; nested foreach
        string[][] combos = new string[arr1.Length * arr2.Length][];

        int ii = 0;
        foreach(var strOne in arr1)
        {
            foreach(var strTwo in arr2)
            {
                string[] combo = new string[2];

                combo[0] = strOne;
                combo[1] = strTwo;
                combos[ii] = combo;

                ii++;
            }
        }

        return combos;
    }
}