class CheckList<T>
{
    public delegate T Getter(List<T> list, int index);
    public delegate void Setter(List<T> list, int index, T value);

    private List<T> list;
    private Getter getter;
    private Setter setter;

    public CheckList(List<T> list, Getter getter, Setter setter)
    {
        this.list = list;
        this.getter = getter;
        this.setter = setter;
    }

    public T this[int index]
    {
        get
        {
            return getter(list, index);
        }
        set
        {
            setter(list, index, value);
        }
    }

    public int Count
    {
        get
        { return list.Count; }
    }

    public void Add(T value)
    {
        list.Add(value);
    }

    public void Remove(T value)
    {
        list.Remove(value);
    }
}

enum EntryType
{
    Root,
    Local,
    House,
    Category,
    Product
}

class Entry
{
    private string name;
    private string country;
    private EntryType type;
    private Entry parent;
    private List<Entry> children;

    public CheckList<Entry> Children;

    private Entry getChild(List<Entry> list, int index)
    {
        return list[index];
    }

    private void setChild(List<Entry> list, int index, Entry value)
    {
        if (value.Type == EntryType.Root) // Класс CheckList существует для этого условия
        {
            throw new ArgumentException();
        }
        list[index] = value;
    }

    public Entry()
    {
        children = new List<Entry>();
        Children = new CheckList<Entry>(children, getChild, setChild);
    }

    public string Name
    {
        get { return name; }
        set
        {
            if (value.Length == 0)
                throw new ArgumentException("некорректное название");

            name = value;
        }
    }

    public string Country
    {
        get { return country; }
        set
        {
            if (value.Length == 0)
                throw new ArgumentException("некорректное название страны");

            country = value;
        }
    }

    public EntryType Type
    {
        get { return type; }
        set { type = value; }
    }

    public Entry Parent
    {
        get
        { return parent; }
        set
        {
            if (type == EntryType.Root
                || type == EntryType.Local && value.Type != EntryType.Root
                || type == EntryType.House && value.Type != EntryType.Local
                || type == EntryType.Category && value.Type != EntryType.House && value.Type != EntryType.Category
                || type == EntryType.Product && value.Type != EntryType.Category)
                throw new ArgumentException("некорректный родитель");

            parent = value;
        }
    }
}