WinUI 3 in desktop: XAML parsing failed

[yv73]

Windows 10 Pro 10.0.19043
Microsoft Visual Studio Community 2019 Version 16.11.1

Steps to reproduce:

File, New, App (WinUI 3 in desktop)
WTS.ProjectConfig.xml:

<xml
    xmlns:genTemplate="http://schemas.microsoft.com/appx/developer/windowsTemplateStudio">

    <genTemplate:Metadata>
        <genTemplate:Item Name="generator" Value="Windows Template Studio"/>
        <genTemplate:Item Name="wizardVersion" Version="v4.1.21179.1" />
        <genTemplate:Item Name="templatesVersion" Version="v4.1.21179.1" />
        <genTemplate:Item Name="projectType" Value="BlankAdvanced" />
        <genTemplate:Item Name="framework" Value="MVVMToolkit" />
        <genTemplate:Item Name="platform" Value="WinUI" />
        <genTemplate:Item Name="appmodel" Value="Desktop" />
    </genTemplate:Metadata>
</xml>

Add, New Item ... Resource Dictionary (WinUI 3) TextBox.xaml
Make the modifications to TextBox.xaml:

   <Style x:Key="TextBoxBaseStyle" TargetType="TextBox">
        <Setter Property="FontSize" Value="{StaticResource LargeFontSize}"/>
    </Style>

LargeFontSize is from /Styles/_FontSizes.xaml:

<x:Double x:Key="LargeFontSize">24</x:Double>

Make the modifications to App.xaml:

    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
                <ResourceDictionary Source="/Styles/_FontSizes.xaml" />
                <ResourceDictionary Source="/Styles/_Thickness.xaml" />
                <ResourceDictionary Source="/Styles/Page.xaml" />
                <ResourceDictionary Source="/Styles/TextBlock.xaml" />
                **<ResourceDictionary Source="/Styles/TextBox.xaml" />**
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>

Build / execute
Observe exception at runtime: 'XAML parsing failed.'
"Cannot find a Resource with the Name/Key LargeFontSize [Line: 13 Position: 37]"

Is there something wrong?

[StephenLPeters]

@yv73 does the _FontSizes.xaml file contain only one resource, LargeFontSize? If so can you try adding a second resource to that dictionary and see if the issue still occurs? there is an optimization for resource dictionaries with only one entry which has bitten us in the past, I wonder if that is causing this.

[yv73]

_FontSizes.xaml is generated with Windows Template Studio (App (WinUI 3 in Desktop)):

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

    <x:Double x:Key="LargeFontSize">24</x:Double>

    <x:Double x:Key="MediumFontSize">16</x:Double>

</ResourceDictionary>

To set TextBox.xaml:

    <Style x:Key="TextBoxBaseStyle" TargetType="TextBox">
        <Setter Property="FontSize" Value="{StaticResource MediumFontSize}"/>
    </Style>

Observe exception at runtime: 'XAML parsing failed.'
"Cannot find a Resource with the Name/Key MediumFontSize [Line: 13 Position: 37]"

No problem if I use

    <Style x:Key="TextBoxBaseStyle" TargetType="TextBox">
        <Setter Property="FontSize" Value="{StaticResource TextStyleLargeFontSize}"/>
    </Style>

TextStyleLargeFontSize is from .nuget\packages\microsoft.projectreunion.winui\0.8.2\lib\net5.0-windows10.0.18362.0\Microsoft.WinUI\Themes\generic.xaml

<x:Double x:Key="TextStyleLargeFontSize">18.14</x:Double>

And LargeFontSize is used in TextBlock.xaml (generated with WTS) without problem:

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

    <!--Common texts-->
    <Style x:Key="PageTitleStyle" TargetType="TextBlock">
        <Setter Property="VerticalAlignment" Value="Center" />
        <Setter Property="FontWeight" Value="SemiLight" />
        <Setter Property="FontSize" Value="{StaticResource LargeFontSize}" />
        <Setter Property="TextTrimming" Value="CharacterEllipsis" />
        <Setter Property="TextWrapping" Value="NoWrap" />
    </Style>

    <Style x:Key="BodyTextStyle" TargetType="TextBlock">
        <Setter Property="FontWeight" Value="Normal" />
        <Setter Property="FontSize" Value="{StaticResource MediumFontSize}" />
        <Setter Property="TextTrimming" Value="CharacterEllipsis" />
        <Setter Property="TextWrapping" Value="Wrap" />
    </Style>

</ResourceDictionary>

Using LargeFontSize directly in MainPage.xaml:

<TextBox Text="TextBox" FontSize="{StaticResource LargeFontSize}"/>

is no problem too.

[mrlacey]

@yv73 I can't reproduce the issue based on the step you've provided. Following them everything works fine for me.

Based on other information above, I suspect there may be more going on than is documented. Because:

• The error message reports the error at line 13, but unless you've got a lot of empty lines, there's no need for TextBlox.xaml to have that many lines so I wonder if there's something else there that may be contributing to the problem.
• WTS generates an app that references Project Reunion package version 0.8.0 but your error message references 0.8.2

If you have a minimal project that shows this, can you zip it up and share it?

[yv73]

I updated Project Reunion package to version 0.8.2. With 0.8.0 same behavior.

App1.zip

[yv73]

Have you reproduced the issue?

[StephenLPeters]

@RealTommyKlein and @fabiant3 FYI

[RealTommyKlein]

I believe the TextBox.xaml and TextBlock.xaml dictionaries need to explicitly include _FontSize.xaml in their MergedDictionaries in order to resolve LargeFontSize and MediumFontSize. TextBox.xaml and TextBlock.xaml are being inserted into Application.Resources at the same time as _FontSize.xaml, so they wouldn't be able to resolve from _FontSize.xaml even though the Application.Resources.MergedDictionaries would suggest so. Making these changes worked for me:

TextBlock.xaml:

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="/Styles/_FontSizes.xaml" />
    </ResourceDictionary.MergedDictionaries>

    <!--Common texts-->
    <Style x:Key="PageTitleStyle" TargetType="TextBlock">
        <Setter Property="VerticalAlignment" Value="Center" />
        <Setter Property="FontWeight" Value="SemiLight" />
        <Setter Property="FontSize" Value="{StaticResource LargeFontSize}" />
        <Setter Property="TextTrimming" Value="CharacterEllipsis" />
        <Setter Property="TextWrapping" Value="NoWrap" />
    </Style>

    <Style x:Key="BodyTextStyle" TargetType="TextBlock">
        <Setter Property="FontWeight" Value="Normal" />
        <Setter Property="FontSize" Value="{StaticResource MediumFontSize}" />
        <Setter Property="TextTrimming" Value="CharacterEllipsis" />
        <Setter Property="TextWrapping" Value="Wrap" />
    </Style>

</ResourceDictionary>

TextBox.xaml:

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App1.Styles">
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="/Styles/_FontSizes.xaml" />
    </ResourceDictionary.MergedDictionaries>

    <Style x:Key="TextBoxBaseStyle" TargetType="TextBox">
        <Setter Property="FontSize" Value="{StaticResource LargeFontSize}"/>
    </Style>

</ResourceDictionary>

[yv73]

Yes, it works for me too. However, TextBlock.xaml works without explicitly including _FontSize.xaml.

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