/// <summary>
/// C#二维数组排列组合算法(每列取一个元素组合)
/// </summary>
/// <param name="args"></param>
/// <returns></returns>
static List<string> ArrayGroup(List<List<string>> args)
{
    List<string> result = new List<string>();
    int counter = 0;

    for (int x = 0; x < args.Count; x++)
    {
        for (int y = 0; y < args[x].Count; y++)
        {
            //1.第1行直接添加
            if (x == 0)
            {
                result.Add(args[x][y]);
            }
            //2.第N行(N>1)处理
            else
            {
                //2.1 统计N-1行元素总数
                if (y == 0)
                {
                    counter = result.Count;
                }

                //2.2 y>0时，复制并添加元素
                if (y > 0)
                {
                    for (int z = 0; z < counter; z++)
                    {
                        result.Add(string.Format("{0}{1}", result[z], args[x][y]));
                    }
                }
                //2.3 y=0放最后来处理，避免声明临时变量存储result
                if (y == args[x].Count - 1)
                {
                    for (int z = 0; z < counter; z++)
                    {
                        result[z] = string.Format("{0}{1}", result[z], args[x][0]);
                    }
                }
            }
        }
    }

    return result;
}

static void Main(string[] args)
{
    List<List<string>> list = new List<List<string>>()
    {
        new List<string>() { "A", "B" },
        new List<string>() { "a", "b", "c" }
    };

    List<string> result = ArrayGroup(list);
    //result.Sort();
    Console.WriteLine(string.Join(",", result.ToArray()));

    Console.ReadKey();
}

static void Main(string[] args)
{
    List<List<string>> list = new List<List<string>>()
    {
        new List<string>() { "A", "B" },
        new List<string>() { "a", "b", "c" }
    };

    var result = list.Aggregate((m, n) => m.SelectMany(t1 => n.Select(t2 => t1 + t2).ToList()).ToList()).ToList();
    Console.WriteLine(string.Join(",", result.ToArray()));

    Console.ReadKey();
}