protected void DisplayNavigationEntry(INavigationEntry entry)
{
if (entry == null)
{
// If this entry is null then simply pass null to the deriving class
DisplayPage(null);
}
else
{
// Cast to the internal NavigationEntry class so we can access all members
// TODO : Try to get rid of the need for this cast? (or check that it is of the correct type and provide alternatives for derived classes)
NavigationEntry internalEntry = (NavigationEntry)entry;
// If the page and VM have not been created then do so
if (internalEntry.ViewLifetimeContext == null)
{
CreatePage(internalEntry);
}
// Navigate to the relevant page
DisplayPage(internalEntry.ViewLifetimeContext.View);
}
}
// *** Private Methods ***
private void DisplaySearchResults(string queryText, string language)
{
// If there are no search results to display then just return
if (queryText == "")
{
return;
}
// Navigate to the search page if it is not currently visible
INavigationEntry currentPage = navigationManager.CurrentPage;
if (currentPage == null || currentPage.PageName != SearchPageName)
{
navigationManager.NavigateTo(SearchPageName);
}
// For all page elements that implement ISearchPage then execute the query
IEnumerable <ISearchPage> searchPages = navigationManager.CurrentPage.GetElements().Where(page => page is ISearchPage).Cast <ISearchPage>();
foreach (ISearchPage searchPage in searchPages)
{
searchPage.PerformQuery(queryText, language);
}
}
protected void CallNavigatingFrom(INavigationEntry entry, NavigationMode navigationMode)
{
if (entry == null)
{
return;
}
foreach (object element in entry.GetElements())
{
if (element is INavigationAware)
{
((INavigationAware)element).NavigatingFrom(navigationMode);
}
}
}
// *** Constructors ***
public PageNavigationEventArgs(INavigationEntry page, NavigationMode navigationMode)
{
// Validate arguments
if (page == null)
throw new ArgumentNullException("page");
if (!Enum.IsDefined(typeof(NavigationMode), navigationMode))
throw new ArgumentException(ResourceHelper.GetErrorResource("Exception_ArgumentException_SpecifiedEnumIsNotDefined"), "navigationMode");
// Set properties
this.page = page;
this.navigationMode = navigationMode;
}
// *** Methods ***
public void GoBack()
{
// Check that we can go back
if (!CanGoBack)
{
throw new InvalidOperationException(ResourceHelper.GetErrorResource("Exception_InvalidOperation_CannotGoBackWithEmptyBackStack"));
}
// Pop the last page from the stack, call NavigationFrom() and dispose any cached items
INavigationEntry oldNavigationEntry = NavigationStack.Pop();
CallNavigatingFrom(oldNavigationEntry, NavigationMode.Back);
if (oldNavigationEntry is NavigationEntry)
{
((NavigationEntry)oldNavigationEntry).DisposeCachedItems();
}
// Display the new current page from the navigation stack
DisplayNavigationEntry(CurrentNavigationEntry);
// If the value of CanGoBack has changed then raise an event
// NB: We can assume that the old value was true otherwise an exception is thrown on entry to this method
if (!CanGoBack)
{
OnCanGoBackChanged();
}
// Call NavigatingTo()
CallNavigatedTo(CurrentNavigationEntry, NavigationMode.Back);
}
protected void DisplayNavigationEntry(INavigationEntry entry)
{
if (entry == null)
{
// If this entry is null then simply pass null to the deriving class
DisplayPage(null);
}
else
{
// Cast to the internal NavigationEntry class so we can access all members
// TODO : Try to get rid of the need for this cast? (or check that it is of the correct type and provide alternatives for derived classes)
NavigationEntry internalEntry = (NavigationEntry)entry;
// If the page and VM have not been created then do so
if (internalEntry.ViewLifetimeContext == null)
CreatePage(internalEntry);
// Navigate to the relevant page
DisplayPage(internalEntry.ViewLifetimeContext.View);
}
}
protected void CallNavigatingFrom(INavigationEntry entry, NavigationMode navigationMode)
{
if (entry == null)
return;
// Fire the NavigatingFrom event
OnNavigatingFrom(new PageNavigationEventArgs(entry, navigationMode));
// Call NavigatingFrom on all page elements
foreach (object element in entry.GetElements())
{
if (element is INavigationAware)
((INavigationAware)element).NavigatingFrom(navigationMode);
}
}
