public MainViewModel(HeaderViewModel header, LivestreamListViewModel livestreamList)
{
Header = header ?? throw new ArgumentNullException(nameof(header));
LivestreamList = livestreamList ?? throw new ArgumentNullException(nameof(livestreamList));
Header.ActivateWith(this);
Header.DeactivateWith(this);
LivestreamList.ActivateWith(this);
LivestreamList.DeactivateWith(this);
}