问题
So my first attempt did everything out of the code behind, and now I'm trying to refactor my code to use the MVVM pattern, following the guidance of the MVVM in the box information.
I've created a viewmodel class to match my view class, and I'm moving the code out of the code behind into the viewmodel starting with the commands.
My first snag is trying to implement a 'Close' button that closes the window if the data has not been modified. I've rigged up a CloseCommand to replace the 'onClick' method and all is good except for where the code tries to run this.Close(). Obviously, since the code has been moved from a window to a normal class, 'this' isn't a window and therefore isn't closeable. However, according to MVVM, the viewmodel doesn't know about the view, so i can't call view.Close().
Can someone suggest how I can close the window from the viewmodel command?
回答1:
You don't need to pass the View instance to your ViewModel layer. You can access the main window like this -
Application.Current.MainWindow.Close()
I see no issue in accessing your main window in ViewModel class as stated above. As per MVVM principle there should not be tight coupling between your View and ViewModel i.e. they should work be oblivious of others operation. Here, we are not passing anything to ViewModel from View. If you want to look for other options this might help you - Close window using MVVM
回答2:
I personally use a very simple approach: for every ViewModel that is related to a closeable View, I created a base ViewModel like this following example:
public abstract class CloseableViewModel
{
public event EventHandler ClosingRequest;
protected void OnClosingRequest()
{
if (this.ClosingRequest != null)
{
this.ClosingRequest(this, EventArgs.Empty);
}
}
}
Then in your ViewModel that inherits from CloseableViewModel, simply call this.OnClosingRequest(); for the Close command.
In the view:
public class YourView
{
...
var vm = new ClosableViewModel();
this.Datacontext = vm;
vm.ClosingRequest += (sender, e) => this.Close();
}
回答3:
My solution to close a window from view model while clicking a button is as follows:
In view model
public RelayCommand CloseWindow;
Constructor()
{
CloseWindow = new RelayCommand(CloseWin);
}
public void CloseWin(object obj)
{
Window win = obj as Window;
win.Close();
}
In View, set as follows
<Button Command="{Binding CloseWindowCommand}" CommandParameter="{Binding ElementName=WindowNameTobeClose}" Content="Cancel" />
回答4:
I do it by creating a attached property called DialogResult:
public static class DialogCloser
{
public static readonly DependencyProperty DialogResultProperty =
DependencyProperty.RegisterAttached(
"DialogResult",
typeof(bool?),
typeof(DialogCloser),
new PropertyMetadata(DialogResultChanged));
private static void DialogResultChanged(
DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
var window = d as Window;
if (window != null && (bool?)e.NewValue == true)
window.Close();
}
public static void SetDialogResult(Window target, bool? value)
{
target.SetValue(DialogResultProperty, value);
}
}
then write this to you XAML, in the window tag
WindowActions:DialogCloser.DialogResult="{Binding Close}"
finally in the ViewModel
private bool _close;
public bool Close
{
get { return _close; }
set
{
if (_close == value)
return;
_close = value;
NotifyPropertyChanged("Close");
}
}
if you change the Close to true, the window will be closed
Close = True;
回答5:
Here is the simplest and pure MVVM solution
ViewModel Code
public class ViewModel
{
public Action CloseAction { get; set; }
private void CloseCommandFunction()
{
CloseAction();
}
}
Here is XAML View Code
public partial class DialogWindow : Window
{
public DialogWindow()
{
ViewModel vm = new ViewModel();
this.DataContext = vm;
vm.CloseAction = new Action(() => this.Close());
}
}
回答6:
This solution is quick and easy. Downside is that there is some coupling between the layers.
In your viewmodel:
public class MyWindowViewModel: ViewModelBase
{
public Command.StandardCommand CloseCommand
{
get
{
return new Command.StandardCommand(Close);
}
}
public void Close()
{
foreach (System.Windows.Window window in System.Windows.Application.Current.Windows)
{
if (window.DataContext == this)
{
window.Close();
}
}
}
}
回答7:
MVVM-light with a custom message notification to avoid the window to process every notificationmessage
In the viewmodel:
public class CloseDialogMessage : NotificationMessage
{
public CloseDialogMessage(object sender) : base(sender, "") { }
}
private void OnClose()
{
Messenger.Default.Send(new CloseDialogMessage(this));
}
Register the message in the window constructor:
Messenger.Default.Register<CloseDialogMessage>(this, nm =>
{
Close();
});
回答8:
This is very similar to eoldre's answer. It's functionally the same in that it looks through the same Windows collection for a window that has the view model as its datacontext; but I've used a RelayCommand and some LINQ to achieve the same result.
public RelayCommand CloseCommand
{
get
{
return new RelayCommand(() => Application.Current.Windows
.Cast<Window>()
.Single(w => w.DataContext == this)
.Close());
}
}
回答9:
using MVVM-light toolkit:
In the ViewModel:
public void notifyWindowToClose()
{
Messenger.Default.Send<NotificationMessage>(
new NotificationMessage(this, "CloseWindowsBoundToMe")
);
}
And in the View:
Messenger.Default.Register<NotificationMessage>(this, (nm) =>
{
if (nm.Notification == "CloseWindowsBoundToMe")
{
if (nm.Sender == this.DataContext)
this.Close();
}
});
回答10:
This is taken from ken2k answer (thanks!), just adding the CloseCommand also to the base CloseableViewModel.
public class CloseableViewModel
{
public CloseableViewModel()
{
CloseCommand = new RelayCommand(this.OnClosingRequest);
}
public event EventHandler ClosingRequest;
protected void OnClosingRequest()
{
if (this.ClosingRequest != null)
{
this.ClosingRequest(this, EventArgs.Empty);
}
}
public RelayCommand CloseCommand
{
get;
private set;
}
}
Your view model, inherits it
public class MyViewModel : CloseableViewModel
Then on you view
public MyView()
{
var viewModel = new StudyDataStructureViewModel(studyId);
this.DataContext = viewModel;
//InitializeComponent(); ...
viewModel.ClosingRequest += (sender, e) => this.Close();
}
回答11:
Given a way, Please check
https://stackoverflow.com/a/30546407/3659387
Short Description
- Derive your ViewModel from INotifyPropertyChanged
- Create a observable property CloseDialog in ViewModel, Change CloseDialog property whenever you want to close the dialog.
- Attach a Handler in View for this property change
- Now you are almost done. In the event handler make DialogResult = true
回答12:
first of all give your window a name like
x:Name="AboutViewWindow"
on my close button I've defined Command and Command Parameter like
CommandParameter="{Binding ElementName=AboutViewWindow}"
Command="{Binding CancelCommand}"
then in my view model
private ICommand _cancelCommand;
public ICommand CancelCommand
{
get
{
if (_cancelCommand == null)
{
_cancelCommand = new DelegateCommand<Window>(
x =>
{
x?.Close();
});
}
return _cancelCommand;
}
}
来源：https://stackoverflow.com/questions/11945821/implementing-close-window-command-with-mvvm