How to Create a NuGet Package with Templated Controls and XAML Without Causing the Runtime Error 'XAML Parsing Fail' in Referencing Projects?

[haonanttt]

Description

When trying to package templated control into nuget package and then consume it in C# WinUI 3 packaged app, the consumer app would fail crash with Microsoft.UI.Xaml.Markup.XamlParseException: 'XAML parsing failed.'

Related issues

• Unable to consume custom and/or templated control using nuget packages in WinUi 3 C#/.Net #7830
• WinUI Packaged projects throws Markup.XamlParseException: 'XAML parsing failed.'  #6452

[haonanttt]

Issue Analysis

This issue happens when trying to pack a 'Debug' NuGet package. NuGet packages created with $(Configuration)==Debug aren't going to work without also explicitly setting DisableEmbeddedXbf to false. Therefore, currently we have workaround to generate 'Debug' NuGet package:

Workaround - Set DisableEmbeddedXbf to false and pack the 'Debug' NuGet package

If you don't want to pack a 'Release' NuGet package and still want a 'Debug' one, you could temporarily set DisableEmbeddedXbf to false and generate the 'Debug' NuGet package

Step1:

Open your templated control project's .csproj file

Step2:

In project's PropertyGroup, add a property <DisableEmbeddedXbf>false</DisableEmbeddedXbf>

Step3:

Save the .csproj file, build your templated control project and pack it. Then you create a 'Debug' NuGet package and you could consume it without 'XAML parsing failed.' error.

Addition

If you don't want to modify your .csproj file, you could also use msbuild command line to run a one-time build with the DisableEmbeddedXbf=false parameter. For example, run msbuild YourProject.csproj /p:DisableEmbeddedXbf=false in your Visual Studio Developer Command Prompt.

Another way to generate a useable NuGet package - Pack a 'Release' NuGet package

NOTE: As the issue only happens with $(Configuration)==Debug, so another way to generate a useable NuGet package is to pack a 'Release' NuGet package. This is not a workaround since 'Release' NuGet package didn't break. This is only another suggestion for dev to generate a useable NuGet package.

When packing your templated control into nuget package, you could modify your configuration manager to pack a 'Release' NuGet package. Then the package could be consumed without 'XAML parsing failed.' error.

Step1:

In Visual Studio, click Build at the top -> select Configuration Manager, open it

Step2:

In configuration manager, temporarily change 'Active solution configuration' from 'Debug' to 'Release'

Step3:

Close configuration manager, build your templated control project and pack it into a 'Release' NuGet package. Then you create a 'Release' NuGet package and you could consume it without 'XAML parsing failed.' error.

[SongOfYouth]

It happens when navigate via frame by reflection: #8601