I see in the MVVM Light toolkit there is a NavigationService. This is very straightforward when you are just navigating to a view and passing no data i.e.
_navigationService.Navigate(typeof(DetailView));
There is an overload on the Navigate method which takes an object parameter i.e.
_navigationService.Navigate(typeof(DetailView), this.SelectedItem.Id);
Question is, how do I then retrieve the parameter in my target view model?
I ended up with the following
public interface IView
{
IViewModel ViewModel { get; }
}
public interface IViewModel
{
void Initialise(object parameter);
}
Then in my view's code behind;
public sealed partial class MyView : IView
{
public ViewModel.IViewModel ViewModel
{
get { return this.DataContext as IViewModel; }
}
public MyView()
{
this.InitializeComponent();
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
if (e.Parameter != null)
{
this.ViewModel.Initialise(e.Parameter);
}
}
}
From there I can now use the parameter in my ViewModel where I am implementing the IViewModel interface.
public void Initialise(object parameter)
{
if (parameter != null)
{
// do something
}
}
Related
I am struggling to register with Autofac a hierarchy of classes and interfaces.
I have an interface IMyService defined as below:
public interface IMyService
{
void DoMyService();
}
And I have two abstract classes with implement this interface and called MyServiceA, and MyServiceB:
public abstract class MyServiceA : IMyService
{
public abstract DoMyService();
}
public abstract class MyServiceB : IMyService
{
public abstract DoMyService();
}
Moreover I have a second-level hierarchy for each of the two aforementioned services: MyServiceA1, MyServiceA2, MyServiceB1 and MyServiceB2:
public class MyServiceA1 : MyServiceA
{
public MyServiceA1() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceA2 : MyServiceA
{
public MyServiceA2() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceB1 : MyServiceB
{
public MyServiceB1() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceB2 : MyServiceB
{
public MyServiceB2() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
I have in input two enums FirstEnum and SecondEnum used to select which of the four concrete types to instantiate:
public enum FirstEnum
{
SvcA,
SvcB
}
public enum SecondEnum
{
Svc1,
Svc2
}
I want to register IMyService and by providing two enums, It will automatically instantiate the good concrete type.
For instance, if I want to resolve an IMyService and I provide FirstEnum.SvcB and SecondEnum.Svc2, it should instantiate the concrete type MyServiceB2 class. Moreover this hierarchy might be updated by adding some other concrete types etc, so I need a generic way of doing it
Does anyone have a clue to help me?
Thanks
If you want to create a specific service dynamically depending on a set of parameters, this is a good use case for an abstract factory:
public interface IMyServiceFactory
{
IMyService Create(FirstEnum e1, SecondEnum e2);
}
public class MyServiceFactory : IMyServiceFactory
{
private readonly ILifetimeScope scope;
public MyServiceFactory(ILifetimeScope scope)
{
if (scope == null)
throw new ArgumentNullException("scope");
this.scope = scope;
}
public IMyService Create(FirstEnum e1, SecondEnum e2)
{
if (e1 == FirstEnum.SvcA)
{
if (e2 == SecondEnum.Svc1)
{
return scope.Resolve<MyServiceA1>();
}
else //svc2
{
return scope.Resolve<MyServiceA2>();
}
}
else //B
{
if (e2 == SecondEnum.Svc1)
{
return scope.Resolve<MyServiceB1>();
}
else //svc2
{
return scope.Resolve<MyServiceB2>();
}
}
}
}
And now your consumer need to get the factory injected instead of the service:
public class MyServiceConsumer
{
private readonly IMyServiceFactory factory;
public MyServiceConsumer(IMyServiceFactory factory)
{
this.factory = factory;
}
public void Do()
{
//var service = this.factory.Create
}
}
Registration :
Autofac.ContainerBuilder builder = new Autofac.ContainerBuilder();
builder.RegisterType<MyServiceA1>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceA2>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceB1>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceB2>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceFactory>().As<IMyServiceFactory>();
builder.RegisterType<MyServiceConsumer>();
//and quick test resolve
var container = builder.Build();
var test = container.Resolve<MyServiceConsumer>();
I am creating UWP app using Template 10. I have created user control like this.
<my:DeviceInfoUserControl OnEndpointTypeChange="{Binding OnEndpointTypeChangeCommand}" Component="{Binding DeviceManagementViewModel,Mode=TwoWay}"></my:DeviceInfoUserControl>
I have Radio Buttons on User Control. I have added User Control on Multiple screens.
This user control has its own ViewModel as well as Some Dependency Properties as follows:
public class DeviceManagementViewModel : ViewModelBase
{
}
public sealed partial class DeviceInfoUserControl : UserControl
{
public bool IsToggled = true;
public DeviceInfoUserControl()
{
this.InitializeComponent();
}
public static readonly DependencyProperty OnEndpointTypeChangeProperty =
DependencyProperty.Register(
"OnEndpointTypeChange",
typeof(ICommand),
typeof(DeviceInfoUserControl), new PropertyMetadata(null));
public ICommand OnEndpointTypeChange
{
get { return (ICommand)GetValue(OnEndpointTypeChangeProperty); }
set { SetValue(OnEndpointTypeChangeProperty, value); }
}
public static readonly DependencyProperty ComponentProperty = DependencyProperty.Register("Component", typeof(DeviceManagementViewModel), typeof(DeviceInfoUserControl), new PropertyMetadata(null));
public DeviceManagementViewModel Component
{
get { return (DeviceManagementViewModel)GetValue(ComponentProperty); }
set { SetValue(ComponentProperty, value); }
}
}
I want to preserve Radio Button Selection across all screens. How should I achieve this?
You have to ensure that the same ViewModel instance is used for all control instance. The XAML way is always create new instance:
<Page.DataContext>
<vm:DetailPageViewModel x:Name="ViewModel" />
</Page.DataContext>
In the Template10's Bootstrapper class with the ResolveForPage method override, you can inject ViewModel's after the page navigation through a custom logic, or through dependency injection LINK
Don't know its better way or not but I have achieved this by making Singletone Viewmodel.
public class DeviceManagementViewModel : ViewModelBase
{
public static readonly DeviceManagementViewModel _instance = new DeviceManagementViewModel ();
private DeviceManagementViewModel ()
{
}
/*Properties and Methods */
}
In Parent Screen ViewModel I have created following property
private DeviceManagementViewModel _deviceManagementViewModel;
public DeviceManagementViewModel DeviceManagementViewModel1
{
get { return _deviceManagementViewModel; }
set { Set(ref _deviceManagementViewModel, value); }
}
I have Instantiated property in Constructor:
public ConfigurationViewModel()
{
DeviceManagementViewModel1 = DeviceManagementViewModel._instance;
}
And on User Control:
<my:DeviceInfoUserControl OnEndpointTypeChange="{Binding OnEndpointTypeChangeCommand}" Component="{Binding DeviceManagementViewModel1,Mode=TwoWay}"></my:DeviceInfoUserControl>
We are using Caliburn Micro for the first time.
We have a AppBootstrapper inherited from ShellViewModel.
Situvation is that VieModels should have the same instance unless it is reset.
we are able to achieve shared or not shared everytime, but releasing the export whenever needed is still a mystery.
public class AppBootstrapper : Bootstrapper<ShellViewModel>
{
private static CompositionContainer _container;
protected override void Configure()
{
try
{
_container = new CompositionContainer(
new AggregateCatalog(AssemblySource.Instance.Select(x => new AssemblyCatalog(x))));
var batch = new CompositionBatch();
batch.AddExportedValue<IWindowManager>(new WindowManager());
batch.AddExportedValue<IEventAggregator>(new EventAggregator());
batch.AddExportedValue(_container);
StyleManager.ApplicationTheme = ThemeManager.FromName("Summer");
_container.Compose(batch);
}
catch (Exception exception)
{
}
}
public static void ReleaseAll()
{
}
protected override object GetInstance(Type serviceType, string key)
{
try
{
var contract = string.IsNullOrEmpty(key) ? AttributedModelServices.GetContractName(serviceType) : key;
var exports = _container.GetExportedValues<object>(contract);
if (exports.Any())
return exports.First();
throw new Exception(string.Format("Could not locate any instances of contract {0}.", contract));
}
catch (ReflectionTypeLoadException ex)
{
foreach (Exception inner in ex.LoaderExceptions)
{
// write details of "inner", in particular inner.Message
}
return null;
}
}
protected override IEnumerable<object> GetAllInstances(Type serviceType)
{
try
{
return _container.GetExportedValues<object>(AttributedModelServices.GetContractName(serviceType));
}
catch (Exception exception)
{
return null;
}
}
protected override void BuildUp(object instance)
{
_container.SatisfyImportsOnce(instance);
}
}
ShellViewModel
[Export(typeof(ShellViewModel))]
public sealed class ShellViewModel : Conductor<IScreen>.Collection.OneActive, IHandle<object>
{
[ImportingConstructor]
public ShellViewModel(CompositionContainer compositionContainer, IEventAggregator eventAggregator)
{
CompositionContainer = compositionContainer;
EventAggregator = eventAggregator;
eventAggregator.Subscribe(this);
Items.Add(compositionContainer.GetExportedValue<AViewModel>());
Items.Add(compositionContainer.GetExportedValue<BViewModel>());
ActivateItem(Items.Single(p => p.DisplayName == AppMessageType.A.ToString()));
}
public IEventAggregator EventAggregator { get; set; }
public CompositionContainer CompositionContainer { get; set; }
public void Handle(object message)
{
//throw new System.NotImplementedException();
}
public void B()
{
ActivateItem(Items.Single(p => p.DisplayName == AppMessageType.B.ToString()));
}
public void A()
{
ActivateItem(Items.Single(p => p.DisplayName == AppMessageType.A.ToString()));
}
public void RESET()
{
AppBootstrapper.ReleaseAll();
ActivateItem(Items.Single(p => p.DisplayName == AppMessageType.A.ToString()));
}
public enum AppMessageType
{
A,
B
}
}
AViewModel
[Export(typeof(AViewModel))]
public sealed class AViewModel : Conductor<IScreen>.Collection.OneActive, IHandle<object>
{
[ImportingConstructor]
public AViewModel(CompositionContainer compositionContainer, IEventAggregator eventAggregator)
{
DisplayName = ShellViewModel.AppMessageType.A.ToString();
CompositionContainer = compositionContainer;
EventAggregator = eventAggregator;
eventAggregator.Subscribe(this);
}
public IEventAggregator EventAggregator { get; set; }
public CompositionContainer CompositionContainer { get; set; }
public void Handle(object message)
{
//throw new System.NotImplementedException();
}
}
BViewModel
[Export(typeof(BViewModel))]
public sealed class BViewModel : Conductor<IScreen>.Collection.OneActive, IHandle<object>
{
[ImportingConstructor]
public BViewModel(CompositionContainer compositionContainer, IEventAggregator eventAggregator)
{
DisplayName = ShellViewModel.AppMessageType.B.ToString();
CompositionContainer = compositionContainer;
EventAggregator = eventAggregator;
eventAggregator.Subscribe(this);
}
public IEventAggregator EventAggregator { get; set; }
public CompositionContainer CompositionContainer { get; set; }
public void Handle(object message)
{
//throw new System.NotImplementedException();
}
}
Now AViewModel and BViewModel have single instance.
Whenever Release Button is clicked i want to have new instance of AViewModel and BViewModel.
Hoping to get a reply soon.
Regards,
Vivek
When working with an IoC container, the only part of your code that should take it as a dependency should be your composition root (i.e. your AppBootstrapper in this case). You shouldn't be injecting or referencing the container anywhere else in your code (except possibly factories).
If you want your ShellViewModel to control the lifetime of your child view models (A and B), then you should consider injecting view model factories into your ShellViewModel (via constructor injection if they are required dependencies).
Your AViewModelFactory would just have a single Create method that returns a new instance of AViewModel, likewise with the BViewModelFactory. You can simply new up your view models directly in the factories. If your view models have large dependency chains themselves, then you could consider adding a reference to your container in the factories, although preferably consider looking into the MEF ExportFactory<T> type.
Trying to learn ASP MVC coming from Linux/LAMP background (in other words I'm a newb) ...
For some reason I can't seem to use a function defined in a controller in another controller.
Here's the function in my MessagesController.cs file:
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
When I try to reference it:
using LemonadeTrader.Models;
using LemonadeTrader.Controllers; // added this to pull the Messages::getMesssagesById
...
ViewBag.messages = lemondb.Messages.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
I get something along the lines of lemondb.Messages does not contain a method called GetMesssagesById.
How do I reference it?
You shouldn't be linking controller methods like this, not to mention that controllers shouldn't be performing data access directly. I would recommend you externalizing this function into a separate class/repository which could be used by both controllers.
Example:
public class MessagesRepository
{
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
}
and then:
public class FooController: Controller
{
public ActionResult Index()
{
var db = new MessagesRepository()
ViewBag.messages = db.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
public class BarController: Controller
{
public ActionResult Index()
{
var db = new MessagesRepository()
ViewBag.messages = db.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
OK, that's the first step. This code could be improved by decoupling the controllers from the repository by introducing an abstraction for this repository:
public interface IMessagesRepository
{
List<Message> GetMessagesById(string username);
}
public class MessagesRepository: IMessagesRepository
{
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
}
then you could use constructor injection for those controllers:
public class FooController: Controller
{
private readonly IMessagesRepository _repository;
public class FooController(IMessagesRepository repository)
{
_repository = repository;
}
public ActionResult Index()
{
ViewBag.messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
public class BarController: Controller
{
private readonly IMessagesRepository _repository;
public class BarController(IMessagesRepository repository)
{
_repository = repository;
}
public ActionResult Index()
{
ViewBag.messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
finally you would configure your DI framework to pass the corresponding implementation into those controllers.
I would also recommend you replacing this ViewBag with a strongly typed view model:
public class MyViewModel
{
public List<Message> Messages { get; set; }
}
and then:
public ActionResult Index()
{
var model = new MyViewModel
{
Messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString())
};
return View(model);
}
Place GetMessageById (and all other methods needed for accessing messages) to separate class and use the class everywhere you need to get Message data.
MessageService service = new MessageService();
ViewBag.messages = service.GetMessagesById(...);
I'm just learning Silverlight and looking at MVVM and Commanding.
Ok, so I have seen the basic RelayCommand implementation:
public class RelayCommand : ICommand
{
private readonly Action _handler;
private bool _isEnabled;
public RelayCommand(Action handler)
{
_handler = handler;
}
public bool IsEnabled
{
get { return _isEnabled; }
set
{
if (value != _isEnabled)
{
_isEnabled = value;
if (CanExecuteChanged != null)
{
CanExecuteChanged(this, EventArgs.Empty);
}
}
}
}
public bool CanExecute(object parameter)
{
return IsEnabled;
}
public event EventHandler CanExecuteChanged;
public void Execute(object parameter)
{
_handler();
}
}
How can I pass a parameter down with a Command using this?
I've seen that you can pass a CommandParameter like this:
<Button Command="{Binding SomeCommand}" CommandParameter="{Binding SomeCommandParameter}" ... />
In my ViewModel, I need to create the Command, but RelayCommand is expecting an Action delegate. Can I implement RelayCommand<T> using Action<T> - if so, how do I do it and how to I use it?
Can anyone give me any practical examples on CommandParameters with MVVM that don't involve using 3rd-party libraries (e.g. MVVM Light) as I want to understand it fully before using existing libraries.
Thanks.
public class Command : ICommand
{
public event EventHandler CanExecuteChanged;
Predicate<Object> _canExecute = null;
Action<Object> _executeAction = null;
public Command(Predicate<Object> canExecute, Action<object> executeAction)
{
_canExecute = canExecute;
_executeAction = executeAction;
}
public bool CanExecute(object parameter)
{
if (_canExecute != null)
return _canExecute(parameter);
return true;
}
public void UpdateCanExecuteState()
{
if (CanExecuteChanged != null)
CanExecuteChanged(this, new EventArgs());
}
public void Execute(object parameter)
{
if (_executeAction != null)
_executeAction(parameter);
UpdateCanExecuteState();
}
}
Is the Base Class for Commands
And this is your Command Property in ViewModel:
private ICommand yourCommand; ....
public ICommand YourCommand
{
get
{
if (yourCommand == null)
{
yourCommand = new Command( //class above
p => true, // predicate to check "CanExecute" e.g. my_var != null
p => yourCommandFunction(param1, param2));
}
return yourCommand;
}
}
in XAML set Binding to Command Property like:
<Button Command="{Binding Path=YourCommand}" .../>
Maybe this article explains what you're looking for. I also had the same problem just minutes ago.
http://www.eggheadcafe.com/sample-code/SilverlightWPFandXAML/76e6b583-edb1-4e23-95f6-7ad8510c0f88/pass-command-parameter-to-relaycommand.aspx