private async Task <bool> NavigationOrchestratorAsync(Type page, object parameter, NavigationMode mode, Func <bool> navigate)
{
try
{
await _navigationOrchestratorAsyncSemaphore.WaitAsync();
this.Log($"Page: {page}, Parameter: {parameter}, NavigationMode: {mode}");
if (page == null)
{
throw new ArgumentNullException(nameof(page));
}
if (navigate == null)
{
throw new ArgumentNullException(nameof(navigate));
}
// this cannot be used for duplicate navigation, except for refresh
if (!Equals(mode, NavigationMode.Refresh))
{
if (Equals(page, CurrentPageType))
{
if (Equals(parameter, CurrentPageParam))
{
return(false);
}
}
}
// fetch current (which will become old)
var fromPage = FrameEx.Content as Page;
var fromParameter = CurrentPageParam;
var fromViewModel = fromPage?.DataContext;
var fromPageName = fromPage?.GetType().ToString();
var fromPageState = await FrameEx2.GetPageStateAsync(fromPage?.GetType());
var from = new NavigationInfo(fromPage?.GetType(), fromParameter, fromPageState);
var toPageName = page?.ToString();
var toPageState = await FrameEx2.GetPageStateAsync(toPageName);
var to = new NavigationInfo(page, parameter, toPageState);
// call fromViewModel.OnNavigatingFromAsync()
var NavigatingFromAsyncResult = await ViewModelActionStrategy.NavigatingFromAsync(fromViewModel, mode, false, from, to, this);
if (NavigatingFromAsyncResult == ContinueResult.Stop)
{
return(false);
}
// raise Navigating event
Two.RaiseNavigatingCancels(parameter, false, mode, to, out var RaiseNavigatingCancelsResult);
if (RaiseNavigatingCancelsResult == ContinueResult.Stop)
{
return(false);
}
// try to resolve the view-model before navigation
var newViewModel = await ViewModelResolutionStrategy.ResolveViewModelAsync(page);
if (newViewModel != null)
{
if (newViewModel is ITemplate10ViewModel t)
{
t.NavigationService = this;
}
await ViewModelActionStrategy.NavigatingToAsync(newViewModel, mode, false, from, to, this);
}
// navigate
var newPage = default(Page);
if (navigate.Invoke())
{
if ((newPage = FrameEx.Content as Page) == null)
{
return(false);
}
CurrentPageParam = parameter;
CurrentPageType = page;
}
else
{
return(false);
}
// fetch current (which is now new)
if (newViewModel != null)
{
newPage.DataContext = newViewModel;
}
else if ((newViewModel = newPage?.DataContext) != null)
{
await ViewModelActionStrategy.NavigatingToAsync(newViewModel, mode, false, from, to, this);
}
// raise Navigated event
Two.RaiseNavigated(new NavigatedEventArgs()
{
Parameter = parameter,
NavigationMode = mode,
PageType = newPage?.GetType(),
});
// call fromViewModel.OnNavigatedFrom()
await ViewModelActionStrategy.NavigatedFromAsync(fromViewModel, mode, false, from, to, this);
// call toTemplate10ViewModel.Properties
if (newViewModel is ITemplate10ViewModel vm)
{
vm.NavigationService = this;
}
// call newViewModel.OnNavigatedToAsync()
await ViewModelActionStrategy.NavigatedToAsync(newViewModel, mode, false, from, to, this);
// finally, all-good
return(true);
}
catch (Exception ex)
{
this.Log(ex.Message, Severities.Error);
Debugger.Break();
throw;
}
finally
{
_navigationOrchestratorAsyncSemaphore.Release();
}
}
void INavigationService2.RaiseNavigatingCancels(object parameter, bool suspending, NavigationMode mode, NavigationInfo toInfo, out ContinueResult cancel)
{
var navigatingDeferral = new Common.DeferralExManager();
var navigatingEventArgs = new NavigatingEventArgs(navigatingDeferral)
{
Parameter = parameter,
Suspending = suspending,
NavigationMode = mode,
TargetPageType = toInfo.PageType,
TargetPageParameter = toInfo.Parameter,
};
Navigating?.Invoke(this, navigatingEventArgs);
cancel = navigatingEventArgs.Cancel ? ContinueResult.Stop : ContinueResult.Continue;
}