Create all combinations of n*m values

Question

Say I have a data structure of IEnumerable> like this:

{
    { A, B }
    { 1, 2, 3 }
    { Z }
}

Answer 1

You could use CartesianProduct method by Eric Lippert for this (taken from here):

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}));                
}

Answer 2

private static IEnumerable<IEnumerable<object>> GetAllCombinations(IEnumerable<IEnumerable<object>> a)
    {
        if (!a.Skip(1).Any())
        {
            return a.First().Select(x => new[] { x });
        }

        var tail = GetAllCombinations(a.Skip(1)).ToArray();
        return a.First().SelectMany(f => tail.Select(x => new[] { f }.Concat(x)));
    }