Wix Toolkit 3.11 util namespace fails to load when building - wix

Question

I am trying to build an installer with Wix 3.11.2 in Visual Studio 2019. I have the extension installed and the toolkit.
I want to use the XmlFile tag in the util namespace to modify the app.config of my installed application.
I have added a reference to C:\Program Files (x86)\WiX Toolset v3.11\bin\WixUtilExtension to the installer project.
I have added the util namespace to the Product.wxs
The xmlnamespace is recognized since I get intellisense etc.
However when building I get the error error CNDL0005: The Fragment element contains an unexpected child element 'util:XmlFile'
This is my Product.wxs:
<?xml version="1.0" encoding="UTF-8"?>
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi"
xmlns:util="http://schemas.microsoft.com/wix/UtilExtension">
<Product Id="DBDA892E-D414-44E9-9F5E-49DCD25E209B" Name="TestWixError" Language="1033" Version="1.0.0.0" Manufacturer="Test" UpgradeCode="41e16593-71c1-4516-8ec3-bc8f4911e3f1">
<Package InstallerVersion="200" Compressed="yes" InstallScope="perMachine" />
<MajorUpgrade DowngradeErrorMessage="A newer version of [ProductName] is already installed." />
<MediaTemplate />
<Feature Id="ProductFeature" Title="TestWixErrorSetup" Level="1">
<ComponentGroupRef Id="ProductComponents" />
</Feature>
</Product>
<Fragment>
<Directory Id="TARGETDIR" Name="SourceDir">
<Directory Id="ProgramFilesFolder">
<Directory Id="INSTALLFOLDER" Name="TestWixErrorSetup" />
</Directory>
</Directory>
</Fragment>
<Fragment>
<ComponentGroup Id="ProductComponents" Directory="INSTALLFOLDER">
<Component Id="MainExecutable" Guid="EA05AA88-F299-4EC2-A64A-4ADAB863C4AC">
<File Id="MainExecutable" Source="$(var.TestWixError.TargetPath)"/>
</Component>
<Component Id="MainPdb" Guid="8ACB76F7-BB83-4EA6-9F58-12CD015E88EC">
<File Source="$(var.TestWixError.TargetDir)$(var.TestWixError.TargetName).pdb" />
</Component>
<Component Id="MainConfig" Guid="39BAFF61-BA1A-42C3-9290-67019F6A6257">
<File Source="$(var.TestWixError.TargetPath).config" />
</Component>
</ComponentGroup>
</Fragment>
<Fragment>
<Property Id="HELLO" Value="Hello from install"/>
<util:XmlFile
Id="UpdateHello"
Action="setValue"
File="$(var.TestWixError.TargetPath).config"
SelectionLanguage="XPath"
Permanent="yes"
ElementPath="/configuration/appSettings/add[\[]#key='Hello'[\] ]/#value"
Value="[HELLO]" />
</Fragment>
</Wix>
The visual studio project is just a .net 4.7.1 console app that displays the value from Hello from the appsettings on the console.
The WixUtilExtension.dll is included in the call to candle.exe as you can see in this commandline (some parts redacted):
C:\Program Files (x86)\WiX Toolset v3.11\bin\candle.exe -dDebug -d"DevEnvDir=C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\Common7\IDE\\" -d"SolutionDir=C:\Users\---\Documents\Projecten\---\TestWixError\\" -dSolutionExt=.sln -dSolutionFileName=TestWixError.sln -dSolutionName=TestWixError -d"SolutionPath=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixError.sln" -dConfiguration=Debug -dOutDir=bin\Debug\ -dPlatform=x86 -d"ProjectDir=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixErrorSetup\\" -dProjectExt=.wixproj -dProjectFileName=TestWixErrorSetup.wixproj -dProjectName=TestWixErrorSetup -d"ProjectPath=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixErrorSetup\TestWixErrorSetup.wixproj" -d"TargetDir=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixErrorSetup\bin\Debug\\" -dTargetExt=.msi -dTargetFileName=TestWixErrorSetup.msi -dTargetName=TestWixErrorSetup -d"TargetPath=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixErrorSetup\bin\Debug\TestWixErrorSetup.msi" -dTestWixError.Configuration=Debug -d"TestWixError.FullConfiguration=Debug|AnyCPU" -dTestWixError.Platform=AnyCPU -d"TestWixError.ProjectDir=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixError\\" -dTestWixError.ProjectExt=.csproj -dTestWixError.ProjectFileName=TestWixError.csproj -dTestWixError.ProjectName=TestWixError -d"TestWixError.ProjectPath=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixError\TestWixError.csproj" -d"TestWixError.TargetDir=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixError\bin\Debug\\" -dTestWixError.TargetExt=.exe -dTestWixError.TargetFileName=TestWixError.exe -dTestWixError.TargetName=TestWixError -d"TestWixError.TargetPath=C:\Users\---\Documents\Projecten\---\TestWixError\TestWixError\bin\Debug\TestWixError.exe" -out obj\Debug\ -arch x86 -ext "C:\Program Files (x86)\WiX Toolset v3.11\bin\\WixUtilExtension.dll" Product.wxs
Things I have tried so far:
Removing the reference, restarting visual studio re-adding the reference
Moving the WixUtilExtension.dll to c:\temp\bin (with all other wix binaries included) and referencing from there.
Moving the WixUtilExtension.dll to the same location as the Product.wxs and referencing from there.
Looking at the WixUtilExtension.dll with ILSpy to verify that it contains a reference to the http://schemas.microsoft.com/wix/UtilExtension namespace (it does in resources it contains an xsd with this namespace)
Any suggestions to get this working are welcome.

Answer 1

Ok,
I am here to answer my own question, hopefully to help someone else in the future.
The util:XmlFile tag needs to be inside a Component tag.
So the fixed fragment looks like this:
<Fragment>
<Property Id="HELLO" Value="Hello from install"/>
<Component Id="TestConfigComponent" Directory="INSTALLFOLDER">
<util:XmlFile
Id="UpdateHello"
Action="setValue"
File="$(var.TestWixError.TargetPath).config"
SelectionLanguage="XPath"
Permanent="yes"
ElementPath="/configuration/appSettings/add[\[]#key='Hello'[\] ]/#value"
Value="[HELLO]" />
</Component>
</Fragment>