Increment id in List<object>

[herczegzoltan]

Hi I am having the following classes and got issue with auto increase id of sub lists.

class A
{
    public int Id { get; set; }
    public string Value { get; set; }
    public List<B> Bs { get; set; }
}

class B
{
    public int Id { get; set; }
    public string Value { get; set; }
    public List<C> Cs { get; set; }
}

class C
{
    public int Id { get; set; }
    public string Value { get; set; }
}

How can I increase automatically the id of the B and C? I can add values but id inside List and List always 0.