/// <summary>
/// Registers the page as a root page.
/// </summary>
/// <param name="page">The page.</param>
public void Register(IAlfredPage page)
{
_rootPages.Add(page);
}
/// <summary>
/// Registers the page as a root page.
/// </summary>
/// <exception cref="ArgumentNullException">
/// Thrown when one or more required arguments are null.
/// </exception>
/// <param name="page"> The page. </param>
public void Register(IAlfredPage page)
{
if (page == null) { throw new ArgumentNullException(nameof(page)); }
if (page.IsRootLevel) { _rootPages.Add(page); }
page.OnRegistered(this);
}