[BuildTools.MSIX] Adding package to project yields WinAppSdkValidateAppxManifestItems error

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#5,348 opened on Apr 18, 2025 0 comments 0 reactions 0 assignees View on GitHub

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area-MSIXBuildTools needs-triage

Dominant language: C++
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Description

### Describe the bug

When attempting to add the latest BuildTools.MSIX package to a blank WinAppSDK/WinUI application, a build error occurs:

> The "Microsoft.Build.Msix.AppxManifest.WinAppSdkValidateAppxManifestItems" task could not be loaded from the assembly C:\Users\Rafael\.nuget\packages\microsoft.windowsappsdk\1.6.250108002\buildTransitive\..\tools\net472\Microsoft.Windows.SDK.BuildTools.MSIX.dll. Could not load file or assembly 'file:///C:\Users\Rafael\.nuget\packages\microsoft.windowsappsdk\1.6.250108002\tools\net472\Microsoft.Windows.SDK.BuildTools.MSIX.dll' or one of its dependencies. The system cannot find the file specified. Confirm that the declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask.

### Steps to reproduce the bug

1. `git clone https://github.com/riverar/repro-211f09d9fccb`
2. `cd repro-211f09d9fccb`
3. `dotnet add package Microsoft.Windows.SDK.BuildTools.MSIX`
4. `dotnet msbuild /p:Configuration=Release /p:AppxPackageDir="MSIXOutputX64\" /p:GenerateAppxPackageOnBuild=true /p:Platform=x64 -bl`
5. Observe warning/failure
6. (Optional) Review `msbuild.binlog`

### Expected behavior

Build to succeed

### Screenshots

_No response_

### NuGet package version

Windows App SDK 1.6.3: 1.6.250108002

### Packaging type

Packaged (MSIX)

### Windows version

Insider Build (xxxxx)

### IDE

Visual Studio 2022-preview, Other, Visual Studio 2022

### Additional context

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First steps

Read the whole issue, then the project's contributing guide.
Comment on the issue to say you are picking it up — it saves two people doing the same work.
Fork the repository and make your change on a branch.
Open a pull request that references the issue number.

Research direction

Start with the linked repro repository and run the documented dotnet msbuild command, then inspect msbuild.binlog and the Microsoft.Windows.SDK.BuildTools.MSIX package path for the missing assembly or dependency. Done means the blank WinAppSDK/WinUI application builds successfully with Microsoft.Windows.SDK.BuildTools.MSIX and generates the MSIX package.

Written by the indexing model from the issue text.

Assessment

Tech stack: cpp
Domain: build-system, desktop
Issue type: Bug
Difficulty: 4/5
Estimated time: 3-5 days
Activity status: Stale
Clarity: Needs clarification
Newbie friendliness: 35/100