BindValidation throws System.NotSupportedException about reactiveui.validation HOT 4 CLOSED

Thank you so much guys!

It's working when I just create a property that call the FindControl method.
And yes I've seen that there is Avalonia.NameGenerator package, and I was wanting to use it afterwards (but because it was not working with the FindControl I didn't check with the NameGenerator package).
Wasn't knowing that calling a method right here could break everything.

Thank you again! I close this.

from reactiveui.validation.

this.BindValidation(ViewModel, viewModel => viewModel.Username, view => view.FindControl<TextBlock>("UsernameError").Text).DisposeWith(disposables);

You can't do complex methods in the expression. You have FindControl. Just point towards a property only.

from reactiveui.validation.

E.g. if you modify your ConnectView as such:

public partial class ConnectView : ReactiveUserControl<ConnectViewModel> {
    public ConnectView() {
        InitializeComponent();
        this.WhenActivated(disposables => {
            // Note the change in the third argument passed to BindValidation ⬇️
            this.BindValidation(ViewModel, vm => vm.Username, v => v.UsernameError.Text)
                .DisposeWith(disposables);
        });
    }

    private TextBlock UsernameError => this.FindControl<TextBlock>("UsernameError");

    private void InitializeComponent() {
            AvaloniaXamlLoader.Load(this);
    }
}

Your example will work, as this change makes the view expression understandable to ReactiveUI.Validation. See https://docs.microsoft.com/en-us/dotnet/api/system.linq.expressions.expression?view=net-5.0 and https://www.reactiveui.net/docs/handbook/data-binding/#types-of-bindings for more info regarding expressions and their role in ReactiveUI code-behind bindings.

A general recommendation is to always declare references to Avalonia controls as such:

private TextBlock UsernameError => this.FindControl<TextBlock>("UsernameError");

And the good news is that there's a library called Avalonia.NameGenerator that will generate such references automatically. See documentation and generated code examples for more info. Don't forget to remove the InitializeComponent method and to use the method generated by Avalonia.NameGenerator btw.

from reactiveui.validation.

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from reactiveui.validation.