public bool Register(MySelectable selectable)
    {
        var reg = registeredSelectables.Add(selectable);

        selectable.DoSetState(initialState);
        return(reg);
    }
    public void Select(MySelectable selectable)
    {
        foreach (var s in registeredSelectables)
        {
            if (s != selectable)
            {
                s.DoSetState(MySelectable.SelectableState.Inactive);
            }
        }

        if (selectable != null)
        {
            selectable.DoSetState(MySelectable.SelectableState.Selected);
        }

        initialState = MySelectable.SelectableState.Inactive;
    }