Can't use x:Bind with Converter in Window

[alexdi220]

Describe the bug
Hi, I've tried to use the x:Bind with IValueConverter. But the project doesn't compile - CS1503 Argument 1: cannot convert from 'TestApp.MainWindow' to 'Microsoft.UI.Xaml.FrameworkElement'. Please take a look at the following code. What I do wrong?

Steps to reproduce the bug

<Window
    x:Class="TestApp.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:TestApp"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">
    <Grid RowDefinitions="Auto, *" x:Name="root">
        <Grid.Resources>
            <local:MyConverter x:Key="MyConverter"/>
        </Grid.Resources>
        <StackPanel Spacing="12"
                    Grid.Row="1">
            <TextBlock Text="{x:Bind MyProperty, Converter={StaticResource MyConverter}}"/>
        </StackPanel>
    </Grid>
</Window>

    public class MyConverter : IValueConverter {
        public object Convert(object value, Type targetType, object parameter, string language) => value;
        public object ConvertBack(object value, Type targetType, object parameter, string language) => value;
    }

    public sealed partial class MainWindow : Window {
        public MainWindow() {
            this.InitializeComponent();            
        }
        public string MyProperty { get; } = "Test";

Expected behavior

Screenshots

Version Info

NuGet package version:

[WinUI 3 - Project Reunion 0.5: 0.5.6]

Windows app type:

UWP	Win32
	Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context

[ranjeshj]

@RealTommyKlein FYI

[RealTommyKlein]

Thanks for the report. The root of your .xaml needs to be a FrameworkElement since the Xaml compiler expects to be able to use the FrameworkElement.Resources property to get its resource dictionary. Since Window isn't a FrameworkElement, the generated code breaks down.

Instead, you should move the UI logic (<Grid RowDefinitions="Auto, *" x:Name="root"> etc.) into its own UserControl, and then set that UserControl as the content of the Window.

[michael-hawker]

Yeah, I too keep getting tripped up that Window isn't a DependencyObject... it's a bit weird.

If the expectation that Window is supposed to just be the host like the implicit Frame created in App.xaml.cs for UWP apps, maybe the File -> New template for WinUI 3 should separate out the MainWindow as also having a MainPage class hosted by it already setup?

This would help lead developers to the proper constructs when building their app and set them up for success vs. having everyone start dumping UI in MainWindow and then getting frustrated.

I mean I really like how the MainWindow is more exposed compared to all the extra logic on Startup that was done in the UWP space, but it's super confusing and bare-bones template when trying to start building an app from afterwards without creating a new Page first.

[Wufus]

This would help lead developers to the proper constructs when building their app and set them up for success vs. having everyone start dumping UI in MainWindow and then getting frustrated.

I mean I really like how the MainWindow is more exposed compared to all the extra logic on Startup that was done in the UWP space, but it's super confusing and bare-bones template when trying to start building an app from afterwards without creating a new Page first.

But we have another problem: CustomTitleBar we can set only with XAML code in MainWindow.xaml, yes?
Using other UI in other page.xaml file will say No for united title with UI.

Best issue about i want to say #2124 with a lot of scrennsots

[qJake]

Coming from a strictly WPF/.NET Framework background, and trying out WinUI 3.x for the first time... this is really non-intuitive, especially when trying to port multi-window applications.

I realize that there is a fundamental difference in how UWP apps behave versus how traditional multi-window applications behave, but there should be an elegant solution to this problem nonetheless.

[KWodarczyk]

Thanks for the report. The root of your .xaml needs to be a FrameworkElement since the Xaml compiler expects to be able to use the FrameworkElement.Resources property to get its resource dictionary. Since Window isn't a FrameworkElement, the generated code breaks down.

Instead, you should move the UI logic (<Grid RowDefinitions="Auto, *" x:Name="root"> etc.) into its own UserControl, and then set that UserControl as the content of the Window.

Thanks for the report. The root of your .xaml needs to be a FrameworkElement since the Xaml compiler expects to be able to use the FrameworkElement.Resources property to get its resource dictionary. Since Window isn't a FrameworkElement, the generated code breaks down.

Instead, you should move the UI logic (<Grid RowDefinitions="Auto, *" x:Name="root"> etc.) into its own UserControl, and then set that UserControl as the content of the Window.

Isn't the Grid the root element ? the converter is defined in grid resources

[lavinders]

Can a sample / example be provided in WinUI docs (if recommendation is to restructure the xaml to expose a usercontrol in order to use a converter / static resource?) so people don't spend cycles figuring out why this simple thing is not working. I am trying to use a boolean to visibility converter and it is so time consuming this simple thing.

[krschau]

Can a sample / example be provided in WinUI docs

@gabbybilka