How do I declare a nested enum?

Question

I want to declare a nested enum like:

\\\\pseudocode
public enum Animal
{
  dog = 0,
  cat = 1
}

private enum dog
{
   bulldog = 0,
   greyhound = 1,
   hus         


        

Answer 1

public enum Animal
{
    CAT_type1= AnimalGroup.CAT,
    CAT_type2 = AnimalGroup.CAT,

    DOG_type1 = AnimalGroup.DOG,
}

public enum AnimalGroup
{
    CAT,
    DOG
}

public static class AnimalExtensions
{
    public static bool isGroup(this Animal animal,AnimalGroup groupNumber)
    {
        if ((AnimalGroup)animal == groupNumber)
            return true;
        return false;
    }
}