Comment faire pour annuler la fermeture de fenêtre en application WPF MVVM

Très bon exemple de cela dans le Modèle de Vue peut être trouvé dans l'article de Nition Nishant, où il utilise les propriétés attachées aux crochet jusqu'à la fenêtre des événements avec les commandes.

Exemple de code d'attachée de comportement (auteur du code: De Nition Nishant)

public class WindowClosingBehavior {
public static ICommand GetClosed(DependencyObject obj) {
return (ICommand)obj.GetValue(ClosedProperty);
}
public static void SetClosed(DependencyObject obj, ICommand value) {
obj.SetValue(ClosedProperty, value);
}
public static readonly DependencyProperty ClosedProperty 
= DependencyProperty.RegisterAttached(
"Closed", typeof(ICommand), typeof(WindowClosingBehavior),
new UIPropertyMetadata(new PropertyChangedCallback(ClosedChanged)));
private static void ClosedChanged(DependencyObject target, DependencyPropertyChangedEventArgs e) {
Window window = target as Window;
if (window != null) {
if (e.NewValue != null) {
window.Closed += Window_Closed;
}
else {
window.Closed -= Window_Closed;
}
}
}
public static ICommand GetClosing(DependencyObject obj) {
return (ICommand)obj.GetValue(ClosingProperty);
}
public static void SetClosing(DependencyObject obj, ICommand value) {
obj.SetValue(ClosingProperty, value);
}
public static readonly DependencyProperty ClosingProperty 
= DependencyProperty.RegisterAttached(
"Closing", typeof(ICommand), typeof(WindowClosingBehavior),
new UIPropertyMetadata(new PropertyChangedCallback(ClosingChanged)));
private static void ClosingChanged(DependencyObject target, DependencyPropertyChangedEventArgs e) {
Window window = target as Window;
if (window != null) {
if (e.NewValue != null) {
window.Closing += Window_Closing;
}
else {
window.Closing -= Window_Closing;
}
}
}
public static ICommand GetCancelClosing(DependencyObject obj) {
return (ICommand)obj.GetValue(CancelClosingProperty);
}
public static void SetCancelClosing(DependencyObject obj, ICommand value) {
obj.SetValue(CancelClosingProperty, value);
}
public static readonly DependencyProperty CancelClosingProperty 
= DependencyProperty.RegisterAttached(
"CancelClosing", typeof(ICommand), typeof(WindowClosingBehavior));
static void Window_Closed(object sender, EventArgs e) {
ICommand closed = GetClosed(sender as Window);
if (closed != null) {
closed.Execute(null);
}
}
static void Window_Closing(object sender, CancelEventArgs e) {
ICommand closing = GetClosing(sender as Window);
if (closing != null) {
if (closing.CanExecute(null)) {
closing.Execute(null);
}
else {
ICommand cancelClosing = GetCancelClosing(sender as Window);
if (cancelClosing != null) {
cancelClosing.Execute(null);
}
e.Cancel = true;
}
}
}
}   

Exemple comment lier les commandes:

<Window 
x:Class="WindowClosingDemo.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:nsmvvm="clr-namespace:NS.MVVM"
nsmvvm:WindowClosingBehavior.Closed="{Binding ClosedCommand}"
nsmvvm:WindowClosingBehavior.Closing="{Binding ClosingCommand}"
nsmvvm:WindowClosingBehavior.CancelClosing="{Binding CancelClosingCommand}">

Commandes "ClosedCommand", "ClosingCommand" et "CancelClosingCommand" devrait être défini dans la Vue Modèle.

internal class MainViewModel : ViewModelBase {
private ObservableCollection<string> log = new ObservableCollection<string>();
public ObservableCollection<string> Log {
get { return log; }
}
private DelegateCommand exitCommand;
public ICommand ExitCommand {
get {
if (exitCommand == null) {
exitCommand = new DelegateCommand(Exit);
}
return exitCommand;
}
}
private void Exit() {
Application.Current.Shutdown();
}
private DelegateCommand closedCommand;
public ICommand ClosedCommand {
get {
if (closedCommand == null) {
closedCommand = new DelegateCommand(Closed);
}
return closedCommand;
}
}
private void Closed() {
log.Add("You won't see this of course! Closed command executed");
MessageBox.Show("Closed");
}
private DelegateCommand closingCommand;
public ICommand ClosingCommand {
get {
if (closingCommand == null) {
closingCommand = new DelegateCommand(ExecuteClosing, CanExecuteClosing);
}
return closingCommand;
}
}
private void ExecuteClosing() {
log.Add("Closing command executed");
MessageBox.Show("Closing");
}
private bool CanExecuteClosing() {
log.Add("Closing command execution check");
return MessageBox.Show("OK to close?", "Confirm", MessageBoxButton.YesNo) == MessageBoxResult.Yes;
}
private DelegateCommand cancelClosingCommand;
public ICommand CancelClosingCommand {
get {
if (cancelClosingCommand == null) {
cancelClosingCommand = new DelegateCommand(CancelClosing);
}
return cancelClosingCommand;
}
}
private void CancelClosing() {
log.Add("CancelClosing command executed");
MessageBox.Show("CancelClosing");
}
}

OriginalL'auteur torpederos