使用此代码：

public static List<string> GenerateCombinations(char[][] characters)
{
    var combinations = new List<string>();
    GenerateCombinations(0, characters, new char[characters.GetLength(0)], combinations);
    return combinations;
}

private static void GenerateCombinations(int level, char[][] characters, char[] current, List<string> combinations)
{
    if (level == characters.GetLength(0))
    {
        combinations.Add(new string(current));
        return;
    }

    foreach (var character in characters[level])
    {
        current[level] = character;
        GenerateCombinations(level + 1, characters, current, combinations);
    }
}

使用示例：

public static void Main()
{
    var characters = new[]
                     {
                         new[] { 'a', 'b' },
                         new[] { 'a', 'b' },
                         new[] { '1', '2' }
                     };

    var combinations = GenerateCombinations(characters);
    foreach (var combination in combinations)
    {
        Console.WriteLine(combination);
    }
}

输出：

aa1
aa2
ab1
ab2
ba1
ba2
bb1
bb2