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Prism. Closing a dialog created with IDialogService

I am trying to use a new IDialogService which was discussed in github issue 1666. A New IDialogService for WPF. I like this new feature but I can't find a solution for one case of using IDialogService in compare with InteractionRequest.
There is a button, pressing on which non-modal dialog is opened. If user press the same button one more time, while dialog still open, dialog close. How this behavior should be implemented in a proper way?
MainWindowViewModel
public class MainWindowViewModel : BindableBase
{
private readonly IDialogService _dialogService;
public DelegateCommand CustomPopupCommand { get; }
public MainWindowViewModel(IDialogService dialogService)
{
_dialogService = dialogService;
CustomPopupCommand = new DelegateCommand(OpenClosePopup);
}
private void OpenClosePopup()
{
// It looks like some additional logic should be implemented here.
// How to save previously opened IDialogAware instance and close it if needed?
_dialogService.Show("CustomPopupView", new DialogParameters("Title=Good Title"), result => { });
}
}
CustomPopupViewModel
public class CustomPopupViewModel : BindableBase, IDialogAware
{
private string _title;
public string Title
{
get => _title;
set => SetProperty(ref _title, value);
}
public DelegateCommand<object> CloseCommand { get; }
public CustomPopupViewModel()
{
CloseCommand = new DelegateCommand<object>(CloseDialog);
}
public event Action<IDialogResult> RequestClose;
public void OnDialogOpened(IDialogParameters parameters)
{
Title = parameters.GetValue<string>(nameof(Title));
}
public void OnDialogClosed()
{
}
public bool CanCloseDialog()
{
return true;
}
public void RaiseRequestClose(IDialogResult dialogResult)
{
RequestClose?.Invoke(dialogResult);
}
private void CloseDialog(object button)
{
RaiseRequestClose(
new DialogResult(button is ButtonResult buttonResult ? buttonResult : ButtonResult.Cancel));
}
}
I have no idea how can it be implemented in proper way because method IDialogService.Show() fully decoupled from knowing about ViewModel and View. Of course except the name of View.

You can always send an event through the event aggregator, probably you have to pass some id in the dialog parameters to close the right dialog if there's more than one open at a time.
But this feels really clunky, I'd prefer to get an IDisposable from Show/ShowDialog that closes the dialog on Dispose.
public CustomPopupViewModel(IEventAggregator eventAggregator)
{
eventAggregator.GetEvent<CloseDialogEvent>().Subscribe( id => { if (id == _id) CloseMe(); } );
}
public void OnDialogOpened(IDialogParameters parameters)
{
_id = parameters.GetValue<string>("id");
}
_dialogService.Show("CustomPopupView", new DialogParameters("id=12345"), result => { });
_eventAggregator.GetEvent<CloseDialogEvent>().Publish("12345");

I find it simplest to use Prism implementation of the subscriber pattern
I use a class that will be used in the pattern and is communicated:
public class DialogStatus
{
public bool DialogResult { get; set; }
}
In my sample, I show you how I do this using a Login Dialog in WPF using Prism 8.0.0.1909
in the App.cs
protected override void OnInitialized()
{
var login = Container.Resolve<LoginDialog>();
var result = login.ShowDialog();
if (result.HasValue && result.Value)
{
base.OnInitialized();
}
else
{
Application.Current.Shutdown();
}
}
in LoginDialog.cs in my Dialogs folder
public partial class LoginDialog : Window
{
public LoginDialog(IEventAggregator eventAggregator)
{
InitializeComponent();
eventAggregator.GetEvent<CloseDialogWindowEvent>().Subscribe(OnCloseWindow);
}
private void OnCloseWindow(DialogStatus obj)
{
base.DialogResult = obj.DialogResult;
}
}
now anywhere in my code, in a ViewModel of view a custom control's view model, the only thing I need to do is pass the IEventAggregator in in the constructor and save it in a field.
private readonly IEventAggregator _eventAggregator;
public LoginControlViewModel(IAuthenticationService authenticationService
, IConnectFileImporterService connectFileImporterService
, IDialogService dialogService
, IEventAggregator eventAggregator)
{
_eventAggregator= eventAggregator;
// the other code
}
I can now close my dialog, and in this sample return true to falls to my OnInitalize in my App.cs from anywhere by calling
_eventAggregator.GetEvent<CloseDialogWindowEvent>().Publish(new CloseDialogWindowEvent() { DialogResult = true });
or
_eventAggregator.GetEvent<CloseDialogWindowEvent>().Publish(new CloseDialogWindowEvent() { DialogResult = false});

If i understand correctly, you want to close the dailog window programmatically instead of clicking the windows's close button, right? If It is true, maybe I can provide you with a solution. Although this method is not very elegant, it is very simple.
My project use mahapps styles, I want use metrowindow as the dailoghost window. Following prism documentation, I register dialoghost window and usercontrol like this:
containerRegistry.RegisterDialogWindow<DialogHost>(nameof(DialogHost));
containerRegistry.RegisterDialog<UserEdit, UserEditViewModel>(nameof(UserEdit));
The UserEidt is a usercontrol, I place a confirm button and a cancel button in UserEidt, and both button binding DelegateCommand in UserEditViewModel. The question is, how can i close dailogwindow by clicking the cancel button?
Here is my solution, firstly define a IDailogViewModel interface:
public interface IDialogViewModel
{
Action CloseDialogWindow { get; set; }
}
Then UserEditViewModel implement this interface:
public class UserEditViewModel : BindableBase, IDialogAware,IDialogViewModel
{
public DelegateCommand CancelCmd { get; private set; }
public Action CloseDialogWindow { get; set; }
public UserEditViewModel()
{
CancelCmd = new DelegateCommand(CloseDialogWindow)
}
private void CloseDialogWindow()
{
CloseDialogWindow.Invoke();
}
}
Infact, when the dialog window popup, the UserEdit will be dialogWindow's content. So in the dialogwindow's loaded event handler, i can get the UserEdit object by using Window.Content, here is the code:
public partial class DialogHost : MetroWindow, IDialogWindow
{
public DialogHost()
{
InitializeComponent();
}
public IDialogResult Result { get; set; }
private void MetroWindow_Loaded(object sender, RoutedEventArgs e)
{
var dialogVM = (IDialogViewModel)((UserControl)Content).DataContext;
dialogVM.CloseDialogWindow += CloseDialogWindow;
}
void CloseDialogWindow()
{
Close();
}
}
Now,after clicking the cancel button, the dialogwindow will be close.

Passing data from one VM to another VM, using Unity and prism EventAggregator

Trying to pass data from one ViewModel to another using prism EventAggregator, but when I debug on the subscriber, the data is null.
Using version 5.0 of prism.
Update
Okay, I have tried implement the EventAggregator using prism 5.0 version. It still dosen't work, but here is what I have done.
1: Create event class
public class RoomsSelectedEvent : PubSubEvent<ObservableCollection<Room>>
{
}
2: Inject IEventAggregator on publisher ViewModel (BookingViewModel)
public class BookingViewModel : INotifyPropertyChanged, IViewBookingViewModel
{
//aggregator
protected readonly IEventAggregator _eventAggregator;
//commands
public ICommand ContinueCommand { get; set; }
public ObservableCollection<Room> RoomsList { get; private set; }
public ObservableCollection<RoomList> DropDownRooms { get; private set; }
public ObservableCollection<CustomerList> DropDownCustomers { get; private set; }
//enities
private readonly IDialogService<ContactDetailsView> _dialogServiceContactView;
private readonly IGetRoomsService _getRoomsService;
public BookingViewModel(IDialogService<ContactDetailsView> dialogServiceContactview, IGetRoomsService GetRoomsService, IEventAggregator eventAggregator)
{
// Injection
_dialogServiceContactView = dialogServiceContactview;
_getRoomsService = GetRoomsService;
_eventAggregator = eventAggregator;
//commands
ContinueCommand = new RelayCommand(ContinueCommand_DoWork, () => true);
}
// Continue Command
public void ContinueCommand_DoWork(object obj)
{
ObservableCollection<Room> RoomsSelected = new ObservableCollection<Room>();
RoomsSelected = _getRoomsService.FilterSelectedRooms(RoomsList);
//Publish event:
_eventAggregator.GetEvent<RoomsSelectedEvent>().Publish(RoomsSelected);
// Open new dialog
_dialogServiceContactView.ShowDialog();
}
}
3: Inject IEventAggregator in subscriber viewModel (ContactViewModel)
public class ContactViewModel : IViewContactViewModel, INotifyPropertyChanged
{
//aggregator
protected readonly IEventAggregator _eventAggregator;
//properties
public ObservableCollection<Room> SelectedRooms { get; set; }
public ContactViewModel(IEventAggregator eventAggregator)
{
//Injection
_eventAggregator = eventAggregator;
//Subscripe to event
_eventAggregator.GetEvent<RoomsSelectedEvent>()
.Subscribe((data) => { SelectedRooms = data; });
}
public ObservableCollection<Room> Rooms
{
get { return SelectedRooms; }
set { SelectedRooms = value; NotifyPropertyChanged(); }
}
}
I have read it's maybe because of the IEventAggregator is not the same in both ViewModels. I'm using Unity to inject it like this code:
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
//view & viewModels
_container = new UnityContainer();
_container.RegisterType<IViewMainWindowViewModel, MainWindow>();
_container.RegisterType<IViewMainWindowViewModel, MenuViewModel>();
_container.RegisterType<IViewBookingViewModel, BookingView>();
_container.RegisterType<IViewBookingViewModel, BookingViewModel>();
_container.RegisterType<IViewContactViewModel, ContactDetailsView>();
_container.RegisterType<IViewContactViewModel, ContactViewModel>();
_container.RegisterType<IGetRoomsService, GetRoomsService>();
_container.RegisterType<IPostReservationService, PostReservationService>();
_container.RegisterType<IGetReservationsListService, GetReservationsListService>();
//types
_container.RegisterType<IEventAggregator, EventAggregator>(new ContainerControlledLifetimeManager());
_container.RegisterType(typeof(IDialogService<>), typeof(DialogService<>));
_container.Resolve<MainWindow>().Show();
}
Found that I need to add the ContainerControlledLifetimeManager, but it still wont work.
When I debug in the subscriber viewModel, I can see that there is an event inside the instance, like on the image:
It wont catch it , thats the problem :(
Today I tried delete all packages I installed (prism 5.0) and go for the Prism.Core (6.1 version)
That resulted in the same, I can see when I debug that the event in published, but when I subscribe, it's still null.

Communication between two viewmodels

I'm newbie in MVVM design pattern, and I have these viewmodels :
ClassAViewModel
public class ClassAViewModel : INotifyPropertyChanged
{
private int _nbre = 0;
public int Nbre
{
get
{
return _nbre;
}
set
{
_nbre = value;
PropertyChanged(this, new PropertyChangedEventArgs("Nbre"));
}
}
#region Events
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
And ClassBViewModel
PUBLIC class ClassBViewModel: INotifyPropertyChanged
{
private Boolean _IsBiggerthanFive = false;
public bool IsBiggerthanFive
{
get
{
return _IsBiggerthanFive;
}
set
{
_IsBiggerthanFive = value;
PropertyChanged(this, new PropertyChangedEventArgs("IsBiggerthanFive"));
}
}
#region Events
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
I need to know if a mecanism of notification between two viewmodels exists , ie in my case if _nbre > 5 in the first viewmodel, the second viewmodel will be notified and the value of _IsBiggerthanFive will be changed. So:
How can two viewmodels communicate between them without instanciate one in the other ?
What is the best way to accomplish this task?

I agree with other commenters that the mediator/pub-sub/event aggregator/messenger is a good way to go. If you're not using an MVVM framework with a built-in solution, then I recommend this simple approach that takes advantage of the Reactive extensions:
public class EventPublisher : IEventPublisher
{
private readonly ConcurrentDictionary<Type, object> subjects
= new ConcurrentDictionary<Type, object>();
public IObservable<TEvent> GetEvent<TEvent>()
{
var subject =
(ISubject<TEvent>) subjects.GetOrAdd(typeof (TEvent),
t => new Subject<TEvent>());
return subject.AsObservable();
}
public void Publish<TEvent>(TEvent sampleEvent)
{
object subject;
if (subjects.TryGetValue(typeof(TEvent), out subject))
{
((ISubject<TEvent>)subject)
.OnNext(sampleEvent);
}
}
}
That's your whole event aggregator. Pass an instance of it into each view model, and store it as a reference. Then create a class to store your event details, let's say "ValueChangedEvent":
public class ValueChangedEvent
{
public int Value
{
get { return _value; }
}
private readonly int _value;
public ValueChangedEvent(int value)
{
_value = value;
}
}
Publish like this from the first view model:
set
{
_nbre = value;
PropertyChanged(this, new PropertyChangedEventArgs("Nbre"));
_eventPublisher.Publish(new ValueChangedEvent(value));
}
Subscribe in the other class using GetEvent:
public class ClassBViewModel: INotifyPropertyChanged, IDisposable
{
private readonly IDisposable _subscriber;
public ClassBViewModel(IEventPublisher eventPublisher)
{
_subscriber = eventPublisher.Subscribe<ValueChangedEvent>(next =>
{
IsBiggerthanFive = next.Value > 5;
});
}
public void Dispose()
{
_subscriber.Dispose();
}
}

A messenger service is a solution. MVVM Light Toolkit has an implementation of this. What you can do with it, is listen to a specific type of message in your viewmodel and handle it through the messenger. http://www.mvvmlight.net/

Bubble events in viewmodels using Caliburn.Micro

I have a screen viewmodel with a search field and some results, composed of multiple, smaller viewmodels: a control for the search field, and a control instance for each result.
My "container" viewmodel (with the search and results) looks like this:
[Export(typeof(ShippingViewModel))]
public class ShippingViewModel : Screen, IHandle<SearchReferenceEvent>
{
private readonly IEventAggregator events;
[ImportingConstructor]
public ShippingViewModel(IEventAggregator events)
{
this.events = events;
this.Search = new QuickSearchViewModel(this.events);
}
public QuickSearchViewModel Search { get; set; }
public void Handle(SearchReferenceEvent message)
{
System.Windows.MessageBox.Show(message.Reference);
}
}
And the "quick search" (with the search fields) viewmodel:
[Export(typeof(QuickSearchViewModel))]
public class QuickSearchViewModel : PropertyChangedBase
{
private readonly IEventAggregator events;
private string currentSearch;
[ImportingConstructor]
public QuickSearchViewModel(IEventAggregator events)
{
this.events = events;
}
public string CurrentSearch // bound to the search field
{
get
{
return this.currentSearch;
}
set
{
this.currentSearch = value;
this.NotifyOfPropertyChange(() => this.CurrentSearch);
}
}
public void SearchReference(string reference) // bound to the search button
{
this.events.Publish(new SearchReferenceEvent(reference));
}
}
The view is displayed as expected, and the search button triggers the SearchReference method.
But the event doesn't seem to be bubbled up to the ShippingViewModel, the Handle is never triggered.
Thanks!

Looks like you're never subscribing to the events in your ShippingViewModel. Try modifying your constructor like so:
[ImportingConstructor]
public ShippingViewModel(IEventAggregator events)
{
this.events = events;
this.events.Subscribe(this); // <= register to receive events
this.Search = new QuickSearchViewModel(this.events);
}

Caliburn micro ViewModel is not picking up a message from another ViewModel

Following my learning of MVVM using Caliburn.micro framework... I'm trying to communicate two viewModels sending data through the EventAggregator like this (code with "no sense", just for test):
MainWindowViewModel.cs
namespace TOP
{
[Export(typeof(MainWindowViewModel))]
public class MainWindowViewModel : Conductor<IScreen>.Collection.OneActive
{
readonly IWindowManager windowManager;
private readonly IEventAggregator events;
private bool _Logged;
[ImportingConstructor]
public MainWindowViewModel(IWindowManager windowManager, IEventAggregator events)
{
DisplayName = "TOP";
this.events = events;
events.Subscribe(this);
this.windowManager = windowManager;
windowManager.ShowDialog(new LoginViewModel(events));
}
public bool Logged
{
get { return _Logged; }
set
{
_Logged = value;
if(_Logged== true)
InitiateApp();
}
}
public void Handle(LoginEvent message)
{
Logged = message.Logged;
}
private void InitiateApp() {
ActivateItem(new TwoWindowViewModel());
}
}
}
LoginViewModel.cs
namespace TOP{
[Export(typeof(IScreen))]
public class LoginViewModel : Screen
{
private readonly IEventAggregator _events;
[ImportingConstructor]
public LoginViewModel(IEventAggregator events)
{
DisplayName = "Login";
_events = events;
Login();
}
public void Login()
{
_events.Publish(new LoginEvent(true));
}
}
}
LoginEvent.cs
namespace TOP
{
public class LoginEvent
{
public LoginEvent(bool logged)
{
Logged = logged;
}
public bool Logged { get; private set; }
}
}
Why the Handle method of MainWindowViewModel is not picking up the published message from LoginViewModel?
Thank you for your responses.

Your MainWindowViewModel needs to implement IHandle<LoginEvent>. You already defined the method with the correct signature, so you only are missing the part where you actually tell the compiler that you implement the interface:
public class MainWindowViewModel
: Conductor<IScreen>.Collection.OneActive, IHandle<LoginEvent>
More info can be found in the documentation.