GetChoiceFieldValues

public static List<string> GetChoiceFieldValues(this SPList list , string fieldName )
{
    try
    {
        SPFieldChoice field = (SPFieldChoice)list.Fields[fieldName];

        if (field == null || string.IsNullOrEmpty(fieldName))
        {
            return null;
        }

        List<string> ret = new List<string>();

        foreach (string str in field.Choices)
        {
            ret.Add(str);
        }

        return ret;
    }
    catch (Exception ex)
    {
        return null;
    }
    
}

List<string> myitems = myspList.GetChoiceFieldValues("CountryNames");