public HomeViewModel(IPageDisplay pageDisplay)
{
// HomeViewModel doesn't implement IPageDisplay, it *consumes* one
// as a dependency (instead of the previous ApplicationViewModel).
// Note, that the instance you're passing still is the ApplicationViewModel,
// so not much has actually changed - but it means you can have another
// implementation of IPageDisplay. You're only linking the classes together
// by the functionality of displaying a page.
_pageDisplay= pageDisplay;
}
HomeViewModel(IPageDisplay pageDisplay) {//constructor stuff}
