I tried this but it is either my misunderstanding or a problem with the design but it seems to result in a circular dependency. As show the DialogService depends on the MainWindow and the MainWindow has a binding to the MainWindowViewModel that uses the DialogService. So the DialogService needs to be constructed after the MainWindow and the MainWindow needs the DataContext set after it is constructed. So the question is how do I build a DialogService with no dependency on Window?
A dialog service is supposed to bring up a dialog which can for example be implemented using a Window or a MessageBox:
public interface IDialogService
{
bool? ShowDialog();
}
public class DialogService : IDialogService
{
public bool? ShowDialog() => new DialogWindow().ShowDialog();
}
DialogWindow.xaml:
<Button IsDefault="True" Click="acceptButton_Click">OK (IsDefault=True)</Button>
<Button IsCancel="True">Cancel (IsCancel=True)</Button>
DialogWindow.xaml.cs:
void acceptButton_Click(object sender, RoutedEventArgs e)
{
// Accept the dialog and return the dialog result
this.DialogResult = true;
}
Window.DialogResult Property
Related
I'm new to WPF and I'm trying to start a little project with a maximum of good practice. I'm using MVVM and dependency injection.
I have a concern which seems to be easy to understand but i can't find an answer (at this step, DataContext is not very clear for me).
The UserControlView of type UserControl contains just a button for testing.
This is the app class :
public App()
{
IServiceCollection services = new ServiceCollection();
services.AddSingleton<MainWindow>();
services.AddSingleton<UserControlViewModel>();
services.AddSingleton<UserControlView>();
_serviceProvider = services.BuildServiceProvider();
}
The user control is included in the Main windows like that :
<Grid>
<views:UserControlView/>
</Grid>
Now, in the OnStartup overrided method :
protected override void OnStartup(StartupEventArgs e)
{
MainWindow = _serviceProvider.GetRequiredService<MainWindow>();
MainWindow.DataContext = _serviceProvider.GetRequiredService<PaymentMeansViewModel>();
MainWindow.Show();
}
Like that it works, my button is correctly binded to the command.
But what is strange for me is that I have to set the 'UserControlViewModel' as the DataContext of the Main Window.
Isn'it possible to bind it to the 'UserControlView', something like :
protected override void OnStartup(StartupEventArgs e)
{
MainWindow = _serviceProvider.GetRequiredService<MainWindow>();
UserControlView testUC = _serviceProvider.GetRequiredService<UserControlView>();
testUC.DataContext = _serviceProvider.GetRequiredService<UserControlViewModel>();
MainWindow.Show();
}
Thanks for help.
Finally I did it.
I think (I hope I'm right) that I understood.
First of all, let's begin with the basic.
A view must have a viewmodel to bind the properties. A usercontrol is a kind of view "encapsulated" in a view. Therefore a usercontrol must have its own viewmodel and the view must have its own viewmodel.
The datacontext of the MainWindow is set in the app onstartup method :
MainWindow = new MainWindow()
{
DataContext = new MainWindowViewModel()
};
MainWindow must implement INotifyPropertyChanged. All view models must implement this interface. We can create a base class which will be derived in the view models :
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler? PropertyChanged;
protected void OnPropertyChanged(string? propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
The DataContext of the usercontrol must be explicit in the xaml of the MainWindow:
<Grid>
<views:UserControlView DataContext="{Binding CurrentViewModel}"/>
</Grid>
"CurrentViewModel" is a DataContext, then it's a ViewModel, and as it is binded, it must be a property of the MainViewModel.
public class MainWindowViewModel : ViewModelBase
{
public ViewModelBase CurrentViewModel { get; }
public MainWindowViewModel()
{
CurrentViewModel=new UserControlViewModel();
}
}
Hope it can help.
I have been trying to set up dependency injection in a wpf application using Unity, but can't seem to fully understand how the views and viewmodels should be set up.
Have looked into another SO post --> Wpf Unity but can't seem to understand it quite yet. I have used Unity before, but just in a MVC application, so I know how to inject it in the contructors.
Here is my views and viewModels in the application.
Views:
MainWindow.xaml
BookingView.xaml
ContactDetailsView.xaml
ReservationsView.xaml
ViewModels:
MenuViewModel (MainWindow uses this viewModel)
BookingViewModel
ContactViewModel
ReservationsViewModel
My ViewModels all have Interfaces implemented, like IMenuViewModel, should the view also have an interface?
I guess that since the MainWindow is the starting point, it should be here to register the container right?
Update:
Have found something, but not sure if I have done it right. Here is what I have done so far!
1: Using startup method in app.cs
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
IUnityContainer container = new UnityContainer();
container.RegisterType<IViewMainWindowViewModel, MainWindow>();
container.RegisterType<IViewMainWindowViewModel, MenuViewModel>();
var mainWindow = container.Resolve<MainWindow>(); // Creating Main window
mainWindow.Show();
}
}
2: Remove uri from start up.
3: Make IViewMainWindowViewModel interface in MainWindow class, the interface is empty.
public interface IViewMainWindowViewModel
{
}
4: Make a reference to this interface in the MainWindow
public partial class MainWindow : Window, IViewMainWindowViewModel
{
public MainWindow(IViewMainWindowViewModel viewModel)
{
InitializeComponent();
DataContext = viewModel;
}
5: Also for the MenuViewModel
public class MenuViewModel : IViewMainWindowViewModel
{
Code not shown!
}
This will not even start the application..
Update 2
My MainWindow class look like this:
public interface IViewMainWindowViewModel
{
}
public partial class MainWindow : Window, IViewMainWindowViewModel
{
public MainWindow(IViewMainWindowViewModel viewModel)
{
InitializeComponent();
DataContext = viewModel;
}
App class now look like this:
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
IUnityContainer container = new UnityContainer();
container.RegisterType<IViewMainWindowViewModel, MainWindow>();
container.RegisterType<IViewMainWindowViewModel, MenuViewModel>();
container.Resolve<MainWindow>().Show();
//Do the same actions for all views and their viewmodels
}
I get an exception on this line when running the application
container.Resolve<MainWindow>().Show();
Update 3
In my MenuViewModel it has two command which will open two views, do I then need to inject those views in the MenuViewModel's constructor or can you just make another empty interface between MenuViewModel and BookingView as an example?
Let me show an example with explanations just for your MainWindows, as for the rest views and viewmodels steps to do are the same.
At first, you should create a contract between View and ViewModel. It shoud be some interface and let it call IViewMainWindowViewModel (keep in mind that name has to be different for other view and viewModels, for example IViewBookingViewViewModel):
public interface IViewMainWindowViewModel
{
/*This interface should not have any methods or commands. It is just
contract between View and ViewModels and helps to decide to Unity
container what it should inject(appropriate viewModel to necessary
View)*/
}
then in your viewmodel we should implement this interface:
public MenuViewModel:IViewMainWindowViewModel
{}
The view should inject this interface MainWindows.xaml.cs:
public partial class MainWindows : UserControl, IContentAView
{
public MainWindows(IViewMainWindowViewModel viewModel)
{
InitializeComponent();
DataContext = viewModel;
}
}
Delete StartupUri and override a method OnStartup in App.xaml.cs:
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
IUnityContainer container = new UnityContainer();
container.RegisterType<IViewMainWindowViewModel, MainWindow>();
container.RegisterType<IViewMainWindowViewModel, MainWindowViewModel >();
container.Resolve<MainWindow>().Show();
//Do the same actions for all views and their viewmodels
}
I am new to MVVM and WPF, trying to use ICommand in WPF and MVVM. Below is the code.
Can someone please help to know why the below code is not working, means nothing happens on button click.
Appreciate your help.
View
<Grid>
<Button Height="40" Width="200" Name="button1" Command="{Binding Path=Click}">Click Me</Button>
</Grid>
App.xaml.cs
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
MainWindow mainWindow = new MainWindow();
MainWindowViewModel vm = new MainWindowViewModel();
mainWindow.DataContext = vm;
}
}
MainWindowViewModel.cs
namespace TestWPFApplication.ViewModel
{
public class MainWindowViewModel
{
private ICommand _click;
public ICommand Click
{
get
{
if (_click == null)
{
_click = new CommandTest();
}
return _click;
}
set
{
_click = value;
}
}
private class CommandTest : ICommand
{
public bool CanExecute(object parameter)
{
return true;
}
public event EventHandler CanExecuteChanged;
public void Execute(object parameter)
{
MessageBox.Show("Hi! Test");
}
}
}
}
It looks like your OnStartup method is instantiating a MainWindow and never showing it. You probably have the StartupUri set in XAML which is creating a different MainWindow with the data context not set.
You could remove the StartupUri and call mainWindow.Show(). Alternatively, you could get rid of the OnStartup method and set up the data context in the main window's constructor.
You don't need to initialize this Window in OnStartup.
In MainWindow constructor after Initialize create instance of ViewModel and it should work.
I would like to use a progressbar in a simple way. I have a query that is run to return data to a grid when a user clicks a button. I would like to start the progressbar when the button is clicked and stop the progressbar when the data is returned to the grid.
I just want the progressbar to continue on (IsIndeterminate="True") to show that there is actually something happening.
Is there any way to bind the start and stop of the progressbar to properties or commands in my view model?
Thanks for any thoughts.
Use the IsIndeterminate property as your property to bind against a property on your ViewModel; mine is titled IsBusy in this example.
public partial class Window1 : Window
{
public MyViewModel _viewModel = new MyViewModel();
public Window1()
{
InitializeComponent();
this.DataContext = _viewModel;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
//this would be a command in your ViewModel, making life easy
_viewModel.IsBusy = !_viewModel.IsBusy;
}
}
public class MyViewModel : INotifyPropertyChanged
{
private bool _isBusy = false;
public bool IsBusy
{
get
{
return _isBusy;
}
set
{
_isBusy = value;
PropertyChangedEventHandler handler = PropertyChanged;
if(handler != null)
handler(this, new PropertyChangedEventArgs("IsBusy"));
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
The XAML is in this instance uses a click event handler for the Button; however in your instance you would simply bind your action which will start your processing to the command on your ViewModel.
<Grid>
<ProgressBar Width="100" Height="25" IsIndeterminate="{Binding IsBusy}"></ProgressBar>
<Button VerticalAlignment="Bottom" Click="Button_Click" Width="100" Height="25" Content="On/Off"/>
</Grid>
As you begin work and end work modifying the IsBusy property on your ViewModel will then start and stop the indeterminate behavior, providing the active/not-active visual appearance you are after.
You could expose a property that you then use to trigger the visibility of the ProgressBar, but you're better off using a control that encompasses a progress bar and exposes a property that turns it on/off. For example, the BusyIndicator in the Extended WPF Toolkit.
I'm new to MVVM and trying to figure out how to close a ChildWindow with the traditional Cancel button using MVVM Light Toolkit.
In my ChildWindow (StoreDetail.xaml), I have :
<Button x:Name="CancelButton" Content="Cancel" Command="{Binding CancelCommand}" />
In my ViewModel (ViewModelStoreDetail.cs), I have :
public ICommand CancelCommand { get; private set; }
public ViewModelStoreDetail()
{
CancelCommand = new RelayCommand(CancelEval);
}
private void CancelEval()
{
//Not sure if Messenger is the way to go here...
//Messenger.Default.Send<string>("ClosePostEventChildWindow", "ClosePostEventChildWindow");
}
private DelegateCommand _cancelCommand;
public ICommand CancelCommand
{
get
{
if (_cancelCommand == null)
_cancelCommand = new DelegateCommand(CloseWindow);
return _cancelCommand;
}
}
private void CloseWindow()
{
Application.Current.Windows[Application.Current.Windows.Count - 1].Close();
}
If you displayed your child window by calling ShowDialog(), then you can simply set the IsCancel property of your button control to "True".
<Button Content="Cancel" IsCancel="True" />
It becomes the same as clicking the X button on the window, or pressing ESC on the keyboard.
Have a look at this articleon MSDN. About half way down there is an approach on how to do this. Basically it uses either uses a WorkspaceViewModel or you implements an interface that exposes and event RequestClose
You then inside the Window's DataContext (if you are setting the ViewModel to it) you can attach to the event.
This is an excerpt from the article (Figure 7). You can adjust it to suit your needs.
// In App.xaml.cs
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
MainWindow window = new MainWindow();
// Create the ViewModel to which
// the main window binds.
string path = "Data/customers.xml";
var viewModel = new MainWindowViewModel(path);
// When the ViewModel asks to be closed,
// close the window.
viewModel.RequestClose += delegate
{
window.Close();
};
// Allow all controls in the window to
// bind to the ViewModel by setting the
// DataContext, which propagates down
// the element tree.
window.DataContext = viewModel;
window.Show();
}
It's been a while since I've used WPF and MVVMLight but yes I think I'd use the messanger to send the cancel event.
In MVVM Light Toolkit the best what you can do is to use Messenger to interact with the View.
Simply register close method in the View (typically in the code behind file) and then send request to close a window when you need it.
We have implemented a NO-CODE BEHIND functionality. See if it helps.
EDIT: Here is there Stackoverflow discussion
Here are some ways to accomplish it.
Send message to your childwindow and set DialogueResult to false on childwindow code-behind.
Make property of DialogueResult and Bind it with childwindow Dialoue CLR property, set it on CancelEval method of CancelCommand.
Create object of Childwindow and set DialogueResult false on CancelEval.
Kind of late to the party but I thought I'd add my input. Borrowing from user841960's answer:
public RelayCommand CancelCommand
{
get;
private set;
}
Then:
SaveSettings = new RelayCommand(() => CloseWindow());
Then:
private void CloseWindow()
{
Application.Current.Windows[Application.Current.Windows.Count - 1].Close();
}
It's a bit cleaner than using an ICommand and works just as well.
So, to sum it all up, the example class would look like so:
public class ChildViewModel
{
public RelayCommand CancelCommand
{
get;
private set;
}
public ChildViewModel()
{
SaveSettings = new RelayCommand(() => CloseWindow());
}
private void CloseWindow()
{
Application.Current.Windows[Application.Current.Windows.Count - 1].Close();
}
}