How to open a sub-window (not a dialog) in the Prism (MVVM pattern)

I was making a two-screen application with WPF.I'm trying to rewrite this to an MVVM pattern using Prism.
Simplified Example:

The WPF window now has the MainWindow, SubWindow class.
MainWindow, Button_Click is called and SubWindow is displayed.
MainWindow.xaml.cs looks like this:

public partial class MainWindow:Window
{
    SubWindow sub;

    private void Button_Click (object sender, RoutedEventArgse)
    {
        if(sub==null)
        {
            sub=new SubWindow();
            sub.Closed+=(s,_e)=>sub=null;
            sub.Show();
         }
         sub.Activate();
    }
}

How do I write equivalent processing in Prism?I don't think it's MVVM-like to generate an instance of SubWindow in View or ViewModel, or Show, Activate, so I don't know how it works anymore.

All you need is

as shown in the code provided.

button to display the SubWindow.If it's already there, just activate it instead of creating a new instance
Not ShowDialog (MainWindow can also be operated)

and so on.

As a matter of concern, I looked at the IDialogService sample (https://prismlibrary.com/docs/wpf/dialog-service.html), but I couldn't find a way to activate the SubWindow on top of multiple screens.

Thank you for your cooperation.

c# wpf mvvm

2022-09-29 22:09

1 Answers

For example,
You can use a delegate to insert features from the "outside" class that invokes the MainWindow.
It also describes how to close the screen;

MainWindowViewModel:

public Action RequestClose;
public Action RequestToSubWindow;
public Action <string > RequestToSubWindow2;

App.xaml.cs:

protected override void OnStartup (StartupEventArgse)
{
    base.OnStartup(e);
    varwnd = new MainWindow();
    varmainVM = new MainWindowViewModel();

    // When the ViewModel asks to be closed, close the window.
    mainVM.RequestClose+=delegate{
        wnd.Close();
    };
    mainVM.RequestToSubWindow+=displaySubWindow;
    mainVM.RequestToSubWindow2+=displaySubWindow2;

    wnd.DataContext=mainVM;
    wnd.Show();
}
// If you do not want to have arguments in ViewModel in SubWindow
private static Action displaySubWindow=()=>{
    var subWnd = new SubWindow();
    var subVM = new SubViewModel();

    // When the ViewModel asks to be closed, close the window.
    subVM.RequestClose+=delegate
    {
        subWnd.Close();
    };
    subWnd.DataContext=subVM;

    subWnd.ShowDialog();
};
// To have ViewModel arguments in SubWindow
private static Action <string > displaySubWindow2=(name_)=>{
    var subWnd2 = new SubWindow2();
    var subVM2 = new Sub2ViewModel(name_);

    // When the ViewModel asks to be closed, close the window.
    subVM2.RequestClose+=delegate
        {
            subWnd2.Close();
        };
    subWnd2.DataContext=subVM2;

    subWnd2.Show();
};

Reference Site:
https://docs.microsoft.com/ja-jp/archive/msdn-magazine/2009/february/patterns-wpf-apps-with-the-model-view-viewmodel-design-pattern

I agree with the question "Not MVVM-like" but it is in the Microsoft documentation.
I can't say that this answer is pretty because it's a blatant code, so if there's any other way, I'd like to use it.

2022-09-29 22:09

If you have any answers or tips

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