WebView2 blank page when publishing WinUI3 app through DevOps pipeline due to 32-bit DLL file being included

Question

I have created a WinUI3 application that uses the Microsoft.Web.WebView2 package (version 1.0.2045.28). When I build or publish the app locally from Visual Studio the app works as expected. When I publish it from an Azure DevOps pipeline however, I only get a blank white page whenever I launch the WebView from within the app.

I have determined that the problem is likely caused by the Microsoft.Web.WebView2.Core.dll file in my app directory being a 32 bit DLL instead of 64 bit when publishing the app via the DevOps pipeline, despite the fact that I have set X64 as the target platform. (Swapping it out afterwards solves the problem).

How can I make sure the DevOps pipeline builds the app with the 64 bit version of WebView2?

Here's the relevant parts from my pipeline:

pool:
  vmImage: 'windows-latest'

variables:
  solution: 'MySolution/MySolution.sln'
  project: 'MySolution/MyApp/MyApp.csproj'
  buildPlatform: 'X64'
  buildConfiguration: 'Release'

steps:
- task: DotNetCoreCLI@2
  inputs:
    command: 'publish'
    publishWebProjects: false
    projects: '$(project)'
    arguments: '--configuration $(buildConfiguration) --output $(Build.ArtifactStagingDirectory) -p:Platform=$(buildPlatform) -p:PublishSingleFile=false --self-contained true'
    zipAfterPublish: true
    modifyOutputPath: false

I also tried to add -r win-x64 to the arguments but it made no difference.

Answer 1

I've found a workaround. The root of the problem seems to be that becuase I'm referencing both Microsoft.Identity.Client (which has WebView2 as a dependency) and Microsoft.Web.WebView2, there is a conflict between the packages: https://github.com/microsoft/microsoft-ui-xaml/issues/5689

To workaround the issue above I have the following lines in my .csproj file, otherwise it won't compile:

    <ErrorOnDuplicatePublishOutputFiles>false</ErrorOnDuplicatePublishOutputFiles>
<PackageReference Include="Microsoft.Identity.Client" Version="4.57.0" />
<PackageReference Include="Microsoft.Web.WebView2" Version="1.0.2088.41" Aliases="webview2" />

...the DLL that ends up in my output folder seems to be a 32 bit version built for .Net core 3.1, probably from the webview2 dependency for Microsoft.Identity.Client.

I discovered that the correct version of the DLL can be found in the obj folder after a build, so I managed to add theese lines to my .csproj file to copy it to the output directory after a build or publish:

 <Target Name="PostBuild" AfterTargets="PostBuildEvent">
    <Exec Command="copy &quot;$(ProjectDir)obj\$(Platform)\$(ConfigurationName)\$(TargetFramework)\$(RuntimeIdentifier)\MsixContent\Microsoft.Web.WebView2.Core.dll&quot; &quot;$(TargetDir)&quot;" />
  </Target>
  <Target Name="PostPublish" AfterTargets="Publish">
    <Exec Command="copy &quot;$(ProjectDir)obj\$(Platform)\$(ConfigurationName)\$(TargetFramework)\$(RuntimeIdentifier)\MsixContent\Microsoft.Web.WebView2.Core.dll&quot; &quot;$(PublishDir)&quot;" />
  </Target>

Not a solution to the actual problem, but with this workaround my app now works as expected.