zzzz.cs

class Orderable : IOrderable
{
    private int order;
    private string name;

    public Orderable(int order, string name)
    {
        this.order = order;
        this.name = name;
    }

    public int Order
    {
        get
        {
            return order;
        }
    }

    public string Name
    {
        get
        {
            return name;
        }
    }
}


interface IOrderable
{
    int Order { get; }
}

sealed class Ordering<T>
    where T : IOrderable
{
    private readonly List<T> list;
    private int last;

    public Ordering(List<T> list)
    {
        this.list = list;
    }

    public void Add(T item)
    {
        if (list.Count == 0)
        {
            list.Add(item);
            last = item.Order;
            return;
        }
        if (last == item.Order)
        {
            list.Add(item);
            return;
        }
        if (last < item.Order)
        {
            list.Add(item);
            last = item.Order;
            return;
        }
        for (int i = 0; i < list.Count; i++)
        {
            if (list[i].Order > item.Order)
            {
                list.Insert(i, item);
                break;
            }
        }
    }
}

interface IIndexable
{
    string Id { get; }
}

sealed class Indexing
{
    public IIndexable Get(string id)
    {
        throw new NotImplementedException();
    }

    public void Add(IIndexable indexable)
    {
    }

    public void Remove(IIndexable indexable)
    {
    }
}