I am trying to get my toplevel for file dialog

[pmankow]

I am running var topLevel = TopLevel.GetTopLevel(this); in my mainviewmodel in order to open a save file dialog. However, I get this error:

CS1503 Argument 1: cannot convert from 'xxxxxxxxxx.ViewModels.MainViewModel' to 'Avalonia.Visual?'

Does anyone know how to remedy this?

[IanRawley]

"this" has to be an Avalonia Visual, and so can't be the ViewModel. Call it in the code behind of the view, or pass a control (likely the view) to the ViewModel.

[thevortexcloud]

If you are using ReactiveUI there is a better way to do this. As I described here: #13484 (reply in thread)

In any case it's considered to be bad practice to try to directly open dialogues from a view model as it does not follow the MVVM pattern properly.

[CodeDevAM]

Alternatively you might set it once at the beginning in your App:

public partial class App : Application
{
    public static TopLevel TopLevel { get; private set; }

    public static MainViewModel MainViewModel { get; private set; }

    public override void OnFrameworkInitializationCompleted()
    {
        MainViewModel = new();

        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktopApp)
        {
            desktopApp.MainWindow = new MainWindow
            {
                DataContext = MainViewModel
            };
            TopLevel = TopLevel.GetTopLevel(desktopApp.MainWindow);
        }
        else if (ApplicationLifetime is ISingleViewApplicationLifetime singleViewPlatform)
        {
            singleViewPlatform.MainView = new MainView
            {
                DataContext = MainViewModel
            };
            TopLevel = TopLevel.GetTopLevel(singleViewPlatform.MainView);
        }

        base.OnFrameworkInitializationCompleted();
    }
}

Then you can access it anywhere it is needed with App.TopLevel.

[NickBarton]

Couldn't make this work Avalonia 11.0.10.
GetTopLevel returns null.

[thevortexcloud]

You should only ever try to access a top level from the code behind of your views. Under MVVM, a view model has nothing to do with a view or top level.

[CodeDevAM]

Couldn't make this work Avalonia 11.0.10.

I don't know for sure, but TopLevel.GetTopLevel() might only produce useful results in a desktop app. (I am using Avalonia 11.x on Windows)

You should only ever try to access a top level from the code behind of your views. Under MVVM, a view model has nothing to do with a view or top level.

I disagree. TopLevel?.StorageProvider?.OpenFilePickerAsync(openOptions) or TopLevel?.Clipboard() might be something that you want to use in your ViewModel.

[thevortexcloud]

You may disagree, but it's still an MVVM violation. The viewmodel is not allowed to know about/directly access anything on the view. There are ways (which I linked in my original comment) to access things like a file picker indirectly from a view model which will not violate MVVM rules.

[timunie]

I have a sample in preview. Unfortunately I don't find the time to finish it due to life throwing in. If you want to check it out, any comment on the samples would be welcome:

https://github.com/timunie/Avalonia.Samples/tree/feature/MVVM_Dialogs/src/Avalonia.Samples/ViewInteraction

Thanks