UWP Packaged WPF .NET 6 app starts a blank window when launched through uri activation and execution alias

Question

I am trying to package a wpf application into an WPF. I use the makeappx executable that is packaged with Windows 10. The WPF in question is just a dummy project. All it has is a button (prototype for something else). The WPF itself works as intended when packaged.

Appxmanifest.xml file content:

<?xml version="1.0" encoding="utf-8"?>
<Package
  xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10"
  xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10"
  xmlns:uap5="http://schemas.microsoft.com/appx/manifest/uap/windows10/5"
  xmlns:uap10="http://schemas.microsoft.com/appx/manifest/uap/windows10/10"
  xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"
  IgnorableNamespaces="uap rescap">

    <Identity Name="WpfApp1" Publisher="CN=Something, O=Another thing, L=City, C=DK" Version="1.0.0.0" ProcessorArchitecture="x86" />
    <Properties>
        <DisplayName>WpfApp1</DisplayName>
        <PublisherDisplayName>Something</PublisherDisplayName>
        <Logo>Images\StoreLogo.png</Logo>
    </Properties>
    <Resources>
        <Resource Language="EN-US" />
    </Resources>
    <Dependencies>
        <TargetDeviceFamily Name="MSIXCore.Desktop" MinVersion="6.1.7601.0" MaxVersionTested="10.0.20348.0" />
        <TargetDeviceFamily Name="Windows.Desktop" MinVersion="10.0.19041.0" MaxVersionTested="10.0.20348.0" />
    </Dependencies>
    <Applications>
        <Application Id="WpfApp1" Executable="WpfApp1.exe" EntryPoint="windows.fullTrustApplication">
            <Extensions>
                <uap5:Extension Category="windows.appExecutionAlias">
                    <uap5:AppExecutionAlias>
                        <uap5:ExecutionAlias Alias="WpfApp1.exe"/>
                    </uap5:AppExecutionAlias>
                </uap5:Extension>
            </Extensions>
            <uap:VisualElements
                BackgroundColor="#464646"
                DisplayName="WpfApp1"
                Square150x150Logo="Images\StoreLogo.png"
                Square44x44Logo="Images\Square44x44Logo.targetsize-24_altform-unplated.png"
                Description="A useful description" />
        </Application>
    </Applications>
</Package>

I have a build pipeline task that packages the application as such:

- task: PowerShell@2
  displayName: 'MSIX Packaging'
  inputs:
    targetType: 'inline'
    script: |
      & 'C:\Program Files (x86)\Windows Kits\10\App Certification Kit\makeappx.exe' pack /d 'path\to\output\' /p test.msix

It gets signed and published to artifacts. I can install it without problem. If I launch it like a normal app it works as intended, i.e. the WPF launches and everything's good. However, if I launch it through either URI activation (WpfApp1:) or, as shown in the example given, execution alias (WpfApp1.exe), it also opens a blank UI window as shown in the image below alongside the WPF application (i.e. two separate windows):

Anyone able to explain why this blank window appears when launching the app through execution alias and how to prevent the blank window from appearing?

Answer 1

Okay, so I finally found the answer to this. Apparently the problem is this line:

<Application Id="WpfApp1" Executable="WpfApp1.exe" EntryPoint="windows.fullTrustApplication">

Apparently Windows.FullTrustApplication is supposed to be written in pascal case instead of camel case, even though Microsoft's own documentation consistently uses camel case. I suspect this is a bug in the framework.

So, in short, the Application element containing the EntryPoint attribute is supposed to look like this:

<Application Id="WpfApp1" Executable="WpfApp1.exe" EntryPoint="Windows.FullTrustApplication">

Hope this helps someone down the line because this took me days to discover because this creates no errors or warnings when building.