We are using Prism 7. Are there any best practices to pass StartupEventArg parameters obtained
from the Prism OnStartup method of App.xaml.cs to other ViewModels. The Event Aggregator is not available in this method so it looks like we can't use this method of passing data to viewmodels.
Thanks
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
if (e.Args.Length > 0)
{
UriBuilder builder = new UriBuilder(e.Args[0]);
var result = HttpUtility.ParseQueryString(builder.Query);
var username = result["username"];
var password = result["password"];
// how to get these to viewmodels
}
}
how to get these to viewmodels?
You create a service that provides the raw arguments to anyone interested, most likely another service that parses them into user name and password.
Example:
internal class EnvironmentCommandLineArgumentsProvider : ICommandLineArgumentsProvider
{
#region ICommandLineArgumentsProvider
public IReadOnlyList<string> Arguments => _arguments.Value;
#endregion
#region private
private readonly Lazy<IReadOnlyList<string>> _arguments = new Lazy<IReadOnlyList<string>>( () => Environment.GetCommandLineArgs() );
#endregion
}
internal class CommandLineInitialCredentialsProvider : IInitialCredentialsProvider
{
public CommandLineInitialCredentialsProvider( ICommandLineArgumentsProvider commandLineArgumentsProvider )
{
_credentials = new Lazy<(string UserName, string Password)>( () =>
{
if (commandLineArgumentsProvider.Arguments.Count > 0)
{
var builder = new UriBuilder(commandLineArgumentsProvider.Arguments[0]);
var result = HttpUtility.ParseQueryString(builder.Query);
return (result["username"], result["password"]);
}
return (null, null);
});
}
#region IInitialCredentialsProvider
public string UserName => _credentials.Value.UserName;
public string Password => _credentials.Value.Password;
#endregion
#region private
private readonly Lazy<(string UserName, string Password)> _credentials;
#endregion
}
Related
I have 3 buttons on one usercontrol (usercontrol1.xaml) in the Window . Now on-click of button 1 ,I want to switch the view to another usercontrol (usercontrol2.xaml), which again have 3 buttons and so on.
How to implement in MVVM Pattern in WPF?
Be aware that im using caliburn micro for this example
private IEventAggregator _eventAggregator => IoC.Get<IEventAggregator>(key: nameof(EventAggregator));
private IWindowManager _windowManager => IoC.Get<IWindowManager>(key: nameof(WindowManager));
public ShellViewModel(IEventAggregator eventAggregator)
{
_eventAggregator.Subscribe(this);
}
public string _firstName;
// public ShellViewModel page = new ShellViewModel();
public string FirstName
{
get {
return _firstName;
}
set
{
_firstName = value;
NotifyOfPropertyChange(() => FirstName);
}
}
public ICommand ConvertTextCommand
{
get { return new DelegateCommand(ConvertText); }
}
void ConvertText()
{
//string url = "https://www.google.com/";
string url = FirstName;
string result;
using (HttpClient client = new HttpClient())
{
using (HttpResponseMessage response = client.GetAsync(url).Result)
{
using (HttpContent content = response.Content)
{
result = content.ReadAsStringAsync().Result;
}
}
}
//(MainWindow)Application.Current.MainWindow).txtForm1TextBox.Text = "Some text";
//Application.Current.Resources.Add("PageSource", result);
// NavigationService.NavigateToViewModel<SecondViewModel>("Hello");
_windowManager.ShowWindow(new PageSourceViewModel(_eventAggregator), null);
_eventAggregator.PublishOnUIThread(result);
}
You can check caliburn micro and see that you can just create a new view model in a window manager instance
here is also 2 links to 2 tutorials that helped me solve this issue for MVVM
https://www.youtube.com/watch?v=laPFq3Fhs8k
https://www.youtube.com/watch?v=9kGcE9thwNw&list=LLy8ROdSzpPJnikdZQ1XPZkQ&index=30&t=0s
the first tutorial will help you to get a general idea. The second will help you with events and you can look back to my code and see how i handled a new window instance.
You can also call the same view model for a new instance of the same window like you said in the question
You will also need to make a boostrapper class. For my example i did it like this.
public class Bootstrapper : BootstrapperBase
{
private readonly SimpleContainer _container =
new SimpleContainer();
public Bootstrapper()
{
Initialize();
}
protected override void Configure()
{
_container.Instance<IWindowManager>(new WindowManager());
_container.Singleton<IEventAggregator, EventAggregator>();
_container.PerRequest<ShellViewModel>();
}
protected override void OnStartup(object sender, StartupEventArgs e)
{
_container.Instance<SimpleContainer>(_container);
_container.Singleton<IWindowManager, WindowManager>(key: nameof(WindowManager))
.Singleton<IEventAggregator, EventAggregator>(key: nameof(EventAggregator));
DisplayRootViewFor<ShellViewModel>();
}
protected override object GetInstance(Type service, string key)
{
return _container.GetInstance(service, key);
}
protected override IEnumerable<object> GetAllInstances(Type service)
{
return _container.GetAllInstances(service);
}
protected override void BuildUp(object instance)
{
_container.BuildUp(instance);
}
}
I have a WPF app and I'm trying to use MEF to load viewmodels and view.
I can't successfully load Views.
The code:
public interface IContent
{
void OnNavigatedFrom( );
void OnNavigatedTo( );
}
public interface IContentMetadata
{
string ViewUri { get; }
}
[MetadataAttribute]
public class ExtensionMetadataAttribute : ExportAttribute
{
public string ViewUri { get; private set; }
public ExtensionMetadataAttribute(string uri) : base(typeof(IContentMetadata))
{
this.ViewUri = uri;
}
}
class ViewContentLoader
{
[ImportMany]
public IEnumerable<ExportFactory<IContent, IContentMetadata>> ViewExports
{
get;
set;
}
public object GetView(string uri)
{
// Get the factory for the View.
var viewMapping = ViewExports.FirstOrDefault(o =>
o.Metadata.ViewUri == uri);
if (viewMapping == null)
throw new InvalidOperationException(
String.Format("Unable to navigate to: {0}. " +
"Could not locate the View.",
uri));
var viewFactory = viewMapping.CreateExport();
var view = viewFactory.Value;
return viewFactory;
}
}
I supposed to use this code like this:
1)Decorate a User control
[Export(typeof(IContent))]
[ExtensionMetadata("CustomPause")]
[PartCreationPolicy(System.ComponentModel.Composition.CreationPolicy.NonShared)]
public partial class CustomPause : Page , IContent, IPartImportsSatisfiedNotification
{
public CustomPause()
{
InitializeComponent();
}
}
2) Compose the parts:
var cv = new CompositionContainer(aggregateCatalog);
var mef = new ViewContentLoader();
cv.ComposeParts(mef);
3) Load the view at runtime given a URI, for example:
private void CustomPause_Click(object sender, RoutedEventArgs e)
{
var vc = GlobalContainer.Instance.GetMefContainer() as ViewContentLoader;
MainWindow.MainFrame.Content = vc.GetView ("CustomPause");
}
Problem is this line in the GetView method fails:
var viewMapping = ViewExports.FirstOrDefault(o =>
o.Metadata.ViewUri == uri);
The query fails and so viewMapping is null but composition seems ok and I can see that ViewExports contains an object of type:
{System.ComponentModel.Composition.ExportFactory<EyesGuard.MEF.IContent, EyesGuard.MEF.IContentMetadata>[0]
I don't know where I'm wrong. Do you have a clue?
Gianpaolo
I had forgot this
[AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
in the MetadataAttribute
I have a UdpClient, firing off a DataRecevied event on my MainWindow:
public partial class MainWindow : Window
{
public static YakUdpClient ClientConnection = new YakUdpClient();
public ClientData;
public MainWindow()
{
InitializeComponent();
Loaded += OnLoaded;
}
private void OnLoaded(object sender, RoutedEventArgs routedEventArgs)
{
ClientData = new ClientData();
ClientConnection.OnDataReceived += ClientConnectionOnDataReceived;
}
private void ClientConnectionOnDataReceived(object sender, MessageEventArgs messageEventArgs)
{
ClientData.Users = messageEvenArgs.ConnectedUsers;
}
}
My ClientData and User classes look as follow:
public class ClientData
{
public List<User> Users {get;set;)
}
public class User
{
public string Name {get;set;}
}
On my MainWindow, I have a UserControl called UserListView which has a ViewModel called UserListViewModel
The ViewModel looks as follow:
public class UserListViewModel: BindableBase
{
public UserListViewModel()
{
//I am sure there are better ways of doing this :(
Users = new ObservableCollection<User>((MainWindow)Application.Current.MainWindow).ClientData.Users
});
private ObservableCollection<User> _users;
public ObservableCollection<User> Users
{
get{ return _users;}
set { this.SetProperty(ref this._users, value); }
}
}
The difficulty I have here, is when the ClientConnectionOnDataReceived event on the MainWindow gets fired, I would like to update my ClientData class, My Viewmodel should then somehow be notified that the list changed, and subsequently update my UI.
Can anyone give me a solid example of how to achieve this using MVVM (Prism) in WPF?
I am new to MVVM, so i am still trying to figure this out.
First of all, there's no obvious reason why the main window should do the subscription.
I'd go for something like this:
create a service that encapsulates the subscription (and subscribes in its constructor)
register that as a singleton
have it implement INotifyPropertyChanged (to notify consumers of a change to Users)
inject the service into UserListViewModel and observe the Users property (see PropertyObserver)
when Users in the service changes, update Users in the user list view model
and best of all, no need for ObservableCollection here :-)
EDIT: example:
interface IUserService : INotifyPropertyChanged
{
IReadOnlyCollection<User> Users
{
get;
}
}
class YakUdpService : BindableBase, IUserService
{
private readonly YakUdpClient _yakUdpClient;
private IReadOnlyCollection<User> _users;
public YakUdpService()
{
_yakUdpClient = new YakUdpClient();
_yakUdpClient.OnDataReceived += ( s, e ) => Users = e.ConnectedUsers;
}
public IReadOnlyCollection<User> Users
{
get
{
return _users;
}
private set
{
SetProperty( ref _users, value );
}
}
}
class UserListViewModel : BindableBase
{
private IReadOnlyCollection<UserViewModel> _users;
private readonly IUserService _userService;
private readonly PropertyObserver<IUserService> _userServiceObserver;
public UserListViewModel( IUserService userService )
{
_userService = userService;
_userServiceObserver = new PropertyObserver<IUserService>( userService );
_userServiceObserver.RegisterHandler( x => x.Users, () => Users = _userService.Users.Select( x => new UserViewModel( x ) ).ToList() );
// ^^^ should use factory in real code
}
public IReadOnlyCollection<UserViewModel> Users
{
get
{
return _users;
}
private set
{
SetProperty( ref _users, value );
}
}
}
and then register the service
Container.RegisterType<IUserService, YakUdpService>( new ContainerControlledLifetimeManager() );
in your bootstrapper or your module's initialization.
I'm struggling to write a test that confirms that I am correctly unsubscribing from an EventAggregator's message when it is closed. Anyone able to point out the (simple) answer?!
Here is the code:
public class ViewModel : BaseViewModel, IViewModel
{
private readonly IEventAggregator eventAggregator;
private SubscriptionToken token;
IssuerSelectedEvent issuerSelectedEvent;
public ViewModel(IView view, IEventAggregator eventAggregator)
{
this.eventAggregator = eventAggregator;
View = view;
issuerSelectedEvent = eventAggregator.GetEvent<IssuerSelectedEvent>();
token = issuerSelectedEvent.Subscribe(SelectedIssuerChanged, true);
}
private void SelectedIssuerChanged(IssuerSelectedCommand obj)
{
Console.WriteLine(obj);
}
public IView View { get; set; }
public override void Dispose()
{
issuerSelectedEvent.Unsubscribe(token);
}
}
The test fails with:
Moq.MockVerificationException : The following setups were not matched:
IssuerSelectedEvent x => x.Unsubscribe(It.IsAny())
Here is the test:
[Test]
public void UnsubscribeFromEventAggregatorOnDispose()
{
var view = new Mock<ICdsView>();
var ea = new Mock<EventAggregator>();
var evnt = new Mock<IssuerSelectedEvent>();
evnt.Setup(x => x.Unsubscribe(It.IsAny<SubscriptionToken>()));
var vm = new CdsIssuerScreenViewModel(view.Object, ea.Object);
vm.Dispose();
evnt.VerifyAll();
}
Here I am verifying that the Unsubscribe was called on the mocked IssuerSelectedEvent
[Test]
public void UnsubscribeFromEventAggregatorOnDispose()
{
var view = new Mock<ICdsView>();
var ea = new Mock<IEventAggregator>();
var evnt = new Mock<IssuerSelectedEvent>();
ea.Setup(x => x.GetEvent<IssuerSelectedEvent>()).Returns(evnt.Object);
var vm = new CdsIssuerScreenViewModel(view.Object, ea.Object);
vm.Dispose();
evnt.Verify(x => x.Unsubscribe(It.IsAny<SubscriptionToken>());
}
If you want to check that the exact same token is passed into the Unsubscribe then you will need a Setup for the Subscribe method that returns a token you create in your test.
You need to tell your EventAggregator mock to return your mocked IssuerSelectedEvent:
ea.Setup(x => x.GetEvent<IssuerSelectedEvent>()).Return(evnt.Object);
The tests needs to be changed to:
[Test]
public void UnsubscribeFromEventAggregatorOnDispose()
{
var view = new Mock<ICdsView>();
var ea = new Mock<IEventAggregator>();
var evnt = new Mock<IssuerSelectedEvent>();
ea.Setup(x => x.GetEvent<IssuerSelectedEvent>()).Returns(evnt.Object);
evnt.Setup(x => x.Unsubscribe(It.IsAny<SubscriptionToken>()));
var vm = new CdsIssuerScreenViewModel(view.Object, ea.Object);
vm.Dispose();
evnt.VerifyAll();
}
I'm looking for the correct version of this class for Caliburn.Micro
public class WebServiceResult : IResult where T : new()
The above signature is from the ContactManager example in the full Caliburn framework.
It does not cut and paste directly into a Micro-based project. There are too many missing classes to use this directly. Thoughts? or anyone know of the replacement?
Event though the underlying infrastructure is very different in Caliburn Micro (which is based on System.Windows.Interactivity), the concepts are pretty much the same.
Here is the CM version:
public class WebServiceResult<T, K> : IResult
where T : new()
where K : EventArgs
{
readonly static Func<bool> ALWAYS_FALSE_GUARD= () => false;
readonly static Func<bool> ALWAYS_TRUE_GUARD = () => true;
private readonly Action<K> _callback;
private readonly Expression<Action<T>> _serviceCall;
private ActionExecutionContext _currentContext;
private Func<bool> _originalGuard;
public WebServiceResult(Expression<Action<T>> serviceCall)
{
_serviceCall = serviceCall;
}
public WebServiceResult(Expression<Action<T>> serviceCall, Action<K> callback)
{
_serviceCall = serviceCall;
_callback = callback;
}
public event EventHandler<ResultCompletionEventArgs> Completed = delegate { };
public void Execute(ActionExecutionContext context)
{
_currentContext = context;
//if you would to disable the control that caused the service to be called, you could do this:
ChangeAvailability(false);
var lambda = (LambdaExpression)_serviceCall;
var methodCall = (MethodCallExpression)lambda.Body;
var eventName = methodCall.Method.Name.Replace("Async", "Completed");
var eventInfo = typeof(T).GetEvent(eventName);
var service = new T();
eventInfo.AddEventHandler(service, new EventHandler<K>(OnEvent));
_serviceCall.Compile()(service);
}
public void OnEvent(object sender, K args)
{
//re-enable the control that caused the service to be called:
ChangeAvailability(true);
if (_callback != null)
_callback(args);
Completed(this, new ResultCompletionEventArgs());
}
private void ChangeAvailability(bool isAvailable)
{
if (_currentContext == null) return;
if (!isAvailable) {
_originalGuard = _currentContext.CanExecute;
_currentContext.CanExecute = ALWAYS_FALSE_GUARD;
}
else if (_currentContext.CanExecute == ALWAYS_FALSE_GUARD) {
_currentContext.CanExecute = _originalGuard ?? ALWAYS_TRUE_GUARD;
}
_currentContext.Message.UpdateAvailability();
}
}