lets assume we have got these classes:
public sealed class Singleton
{
private static readonly Singleton instance = new Singleton();
private Controller controller;
private uControl uc; //user control
public static Singleton Instance
{
get { return Singleton.instance; }
}
public Controller GetController
{
get
{
if (this.controller == null)
{
this.controller = new Controller();
}
return this.controller;
}
}
public uControl UC
{
get
{
if (this.uc == null)
{
this.uc = new uControl();
}
return this.uc;
}
}
}
public uControl : UserControl
{
Controller controller = Singleton.Instance.GetController;
// Do some work with controller class here ...
}
public Form1 : Form
{
public Form1()
{
this.Controls.Add(Singleton.Instance.UC);
}
}
public Form2 : Form
{
public Form2()
{
this.Controls.Add(Singleton.Instance.UC);
}
}
Is it possible to add user control uControl via Singleton into two different forms and expect them to work correctly while accessing the same controller class?
When I try this only the form instantiated first will be able to display the uControl correctly. The other Form will get the uControll OK, but only empty space appears in the form where the user control should be ...
you most definitely don't want to do that. the events of the control, it's position and a lot of other things of the user control are coming from it's parent control, and associate with it. what you can do is return a new user control with your own properties in it such as width and event handlers
Related
I have a problem with MVVM pattern and binding collection. My ViewModel provides a collection to the View but to get this collection I use this:
public BindingList<Car> BindingListCars { get; set; }
public CarsVm()
{
BindingListVoiture = carServices.ListCars;
}
When I bind my View on this List it's as if I bind directly my View on the Model because they use the same reference. So when I edit one property of a Car, the model is directly edited without using carServices validation method.
What is the best solution to correct this problem ?
Do I have to expose a copy of my Model to my View to not edit directly my Model from the View?
Do I have to use BindingList in my Model and subsribe to ListChanged in my carServices to validate each change?
You should either perform the validation directly in the Car class itself or expose wrapper objects instead of exposing the "real" Car objects to the view.
The following sample code should give you the idea about what I mean:
//the "pure" model class:
public class Car
{
public string Model { get; set; }
}
public class CarService
{
public List<CarWrapper> ListCar()
{
List<Car> cars = new List<Car>(); //get your Car objects...
return cars.Select(c => new CarWrapper(c, this)).ToList();
}
public bool Validate()
{
//
return true;
}
}
public class CarWrapper
{
private readonly Car _model;
CarService _service;
public CarWrapper(Car model, CarService service)
{
_model = model;
_service = service;
}
//create a wrapper property for each property of the Car model:
public string Model
{
get { return _model.Model; }
set
{
if(_service.Validate())
_model.Model = value;
}
}
}
Obviously if you expose an IEnumerable<Car> from your view model for the view to bind, you are effectively bypassing any validation that is dedined outside of the Car class if the view is able to set any properties of the Car class.
Thanks for your answer mm8,
With this solution I have to create one wrapper per class which need outside validation. It add work and during refactoring we have to edit the class and the Wrapper.
What do you think about this solution :
I put my list of vehicle in a binding list
My service subscribe to ListChanged event of this list
My service implement INotifyDataErrorInfo
For each modification in this list validation is executed
If there is an error ErrorsChanged event is raised
The view model subsribe to this event and retrieve error Data.
The view model subsribe to this event and retrieve error Data.
For example :
My services implementation :
public class VehicleServices : INotifyDataErrorInfo
{
private BindingList<Vehicle> _bindingListCar
public BindingList<Vehicle> BindingListCar
{
get return _bindingListCar;
}
private readonly Dictionary<string, ICollection<string>>
_validationErrors = new Dictionary<string, ICollection<string>>();
//INotifyDataErrorInfo implementation
public IEnumerable GetErrors(string propertyName)
public bool HasErrors
private void RaiseErrorsChanged(string propertyName)
public VehicleServices()
{
_bindingListCar = GetVehicles();
_bindingListCar.ListChanged += BindingListVehicleChanged;
}
private void BindingListVehicleChanged(object sender, ListChangedEventArgs e)
{
//Only modification is managed
if (e.ListChangedType != ListChangedType.ItemChanged) return;
switch(e.PropertyDescriptor.Name)
//Validate each property
//if there is ErrorsChanged is raised
}
}
And my ViewModel
public class CarVm : BindableBase
{
private ICollection<string> _errors;
public ICollection<string> Error
{
get
{
return _errors;
}
set
{
SetProperty(ref _errors, value);
}
}
private VehicleServices _carServices;
public BindingList<Vehicle> BindingListCar { get; set; }
public CarVm(VehicleServices carServices)
{
_carServices = carServices;
BindingListCar = new BindingList<Vehicle>(_carServices.BindingListCar);
_carServices.ErrorsChanged += _carServices_ErrorsChanged;
}
private void _carServices_ErrorsChanged(object sender, DataErrorsChangedEventArgs e)
{
Error = _carServices.ValidationErrors[e.PropertyName];
}
}
Do you think this is a good practice ?
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 haveViewModel1 and View1 associated with it. I start dialog window from ViewModel2 (some another viewmodel) using IWindowManager object. The code from ViewModel2 class:
windowManager.ShowDialog(new ViewModel());
So, I have Dialog Window with View1 user control.
My answer is next - I can close that dialog window using red close button, but how to close it using my specific button (contained in View1 user control), something like "Cancel" button with close command (Command={Binding CancelCommand}), CancelCommand of course is contained in ViewModel1 class.
It's even easier if your view model extends Caliburn.Micro.Screen:
TryClose();
You can get the current view (in your case the dialog window) with implementing the IViewAware interface on your ViewModel. Then you can call Close on the the view (the Window created as the dialog) when your command is executed.
The easiest why is to derive from ViewAware:
public class DialogViewModel : ViewAware
{
public void ExecuteCancelCommand()
{
(GetView() as Window).Close();
}
}
If you are not allowed to derive you can implement it yourself:
public class DialogViewModel : IViewAware
{
public void ExecuteCancelCommand()
{
dialogWindow.Close();
}
private Window dialogWindow;
public void AttachView(object view, object context = null)
{
dialogWindow = view as Window;
if (ViewAttached != null)
ViewAttached(this,
new ViewAttachedEventArgs(){Context = context, View = view});
}
public object GetView(object context = null)
{
return dialogWindow;
}
public event EventHandler<ViewAttachedEventArgs> ViewAttached;
}
Note: I've used Caliburn.Micro 1.3.1 for my sample.
A cleaner way (Subject of personal taste) that I use alot is to use the IResult pattern, this way you abstract the Window implemenation
Viewmodel
public IEnumerable<IResult> CloseMe()
{
yield return new CloseResult();
}
Result code
public class CloseResult : Result
{
public override void Execute(ActionExecutionContext context)
{
var window = Window.GetWindow(context.View);
window.Close();
base.Execute(context);
}
}
public abstract class Result : IResult
{
public virtual void Execute(ActionExecutionContext context)
{
OnCompleted(this, new ResultCompletionEventArgs());
}
protected virtual void OnCompleted(object sender, ResultCompletionEventArgs e)
{
if (Completed != null)
Completed(sender, e);
}
public event EventHandler<ResultCompletionEventArgs> Completed;
}
edit (Only needed for IoC): If you wanna take it a step further you do a base class for all screens
public abstract class ShellPresentationModel : Screen
{
public ShellPresentationModel(IResultFactory resultFactory)
{
Result = resultFactory;
}
public IResultFactory Result { get; private set; }
}
This way you can inject dependencies with a IoC much easier, then your VIewmodel close method will look like this
public IEnumerable<IResult> CloseMe()
{
yield return Result.Close();
}
An example on a IResult that uses dependency can be
public class ShowDialogResult<TModel> : Result
{
private readonly IWindowManager windowManager;
private readonly TModel model;
private Action<TModel> configure;
public ShowDialogResult(IWindowManager windowManager, TModel model)
{
this.windowManager = windowManager;
this.model = model;
}
public IResult Configure(Action<TModel> configure)
{
this.configure = configure;
return this;
}
public override void Execute(ActionExecutionContext context)
{
if(configure != null)
configure(model);
windowManager.ShowDialog(model);
base.Execute(context);
}
}
edit Just noticed that i forgot to add an example of the above IoC exmaple, here goes
With a child IoC container pattern it would look like this
public IEnumerable<IResult> ShowDialog()
{
yield return Result.ShowDialog<MyViewModel>();
}
Without a child container pattern you would need to inject parent dependeync into the child manually
yield return Result.ShowDialog<MyViewModel>().Configure(m => m.SomeData = this.SomeData);
I have like 2 or 3 different forms and for example for my mainForm, I would like to access the object in settingsForm. How do I do that.
You need to expose that object, via a public property on settingsForm.
e.g.
In your settings form:
public Object MyObject
{
get { return myobject; }
}
then, on your main form, your can say;
settingsForm sf = new settingsForm();
sf.Show();
...
Console.Write(sf.MyObject.Text);
So. let's say settingsForm has a textbox that stores a value you want.
If you need access to the entire text box, you'd add a property on settings forms....
public TextBox textbox1
{
get { return textbox1; }
}
then, any form that instantiates and uses settingsForm, can use textbox1.
If you only want to access the value in textbox1, you'd only expose its Text property.
public string TextBoxValue
{
get { return textbox1.Text; }
}
public partial class mainForm : Form
{
settingForm settingObject;
public mainForm(settingForm settingObject)
{
InitializeComponent();
this.settingObject= settingObject;
}
}
the above code shows a simple way of how you access the object.
Hi I have a beginner problem. I have shell (it is wpf window) and in this shell is screen (it is an user control / view model).
I would like open new window from view model, not show user control in shell.
So I create new window - ChatView
<Window x:Class="Spirit.Views.ChatView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:extToolkit="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit.Extended" Title="ChatView" Height="545" Width="763">
<Grid Margin="4,4,4,4">
</Grid>
</Window>
Export ChatViewModel with MEF.
public interface IChatViewModel
{
}
[Export("ChatScreen",typeof(IChatViewModel))]
public class ChatViewModel
{
}
In view model I have this method:
With ShowScreen class help me Mr.Marco Amendola. It look likes this:
public class ShowScreen : IResult
{
readonly Type _screenType;
readonly string _name;
[Import]
public IShellViewModel Shell { get; set; }
Action<object> _initializationAction = screen => { };
public ShowScreen InitializeWith<T>(T argument)
{
_initializationAction = screen =>
{
var initializable = screen as IInitializable<T>;
if (initializable != null)
initializable.Initialize(argument);
};
return this;
}
public ShowScreen(string name)
{
_name = name;
}
public ShowScreen(Type screenType)
{
_screenType = screenType;
}
public void Execute(ActionExecutionContext context)
{
var screen = !string.IsNullOrEmpty(_name)
? IoC.Get<object>(_name)
: IoC.GetInstance(_screenType, null);
_initializationAction(screen);
Shell.ActivateItem(screen);
Completed(this, new ResultCompletionEventArgs());
}
public event EventHandler<ResultCompletionEventArgs> Completed = delegate { };
public static ShowScreen Of<T>()
{
return new ShowScreen(typeof(T));
}
}
My problem is if I try show new window it doesn’t works, it works only if I show new user control in shell(window).
I would like achieve behavior something like in skype. You have a main window with listbox, you double clicked on item and it show new chat window.
Main window can publish with EventAggregator on chat window and also chat window can publish on main window. This is my goal.
I know that I can not use class ShowScreen on showing new Window. I would like to know what is correct way to create new window from view model and inject event aggregator
to this vie model.
Any advice? Thank for your help and time.
Have you looked at WindowManager.Show or WindowManager.ShowDialog? Rob has a sample at http://caliburnmicro.codeplex.com/wikipage?title=The%20Window%20Manager. You can inject this dependency into your view model as IWindowManager.
I'm using this. Maybe could save a question about "where's the code ?".
DialogHelper:
public class DialogHelper
{
public void ShowDialog<T>(params Object[] param) where T : class
{
var windowManager = new WindowManager();
T viewModel = Activator.CreateInstance(typeof(T), param) as T;
windowManager.ShowWindow(viewModel);
}
}
How to use:
Without constructor parameter:
Dialog.ShowDialog<TestTableViewModel>();
With constructor paramater:
Dialog.ShowDialog<TestTableViewModel>(dt);
Note that I'm not using MEF