Microsoft.Build.MsixPackaging — reusable MSBuild SDK for multi-app MSIX packaging

[shmuelie]

Summary

New SDK project: Microsoft.Build.MsixPackaging — a reusable MSBuild SDK that packages multiple .NET projects into a single sideloadable MSIX using per-project AppxFragment.xml manifest entries. Replaces WAP/DesktopBridge with a transparent, SDK-style workflow.

SDK-tool discovery, MSIX packing, and signing use the compiled MSBuild tasks in the Microsoft.Windows.SDK.BuildTools.MSIX package, so the SDK relies on supported Windows SDK tooling.

Consumer Experience

<Project Sdk="Microsoft.Build.MsixPackaging/1.0.0">
  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <MsixFileName>MyAppBundle</MsixFileName>
    <MsixPackageVersion>1.0.0.0</MsixPackageVersion>
  </PropertyGroup>
  <ItemGroup>
    <ProjectReference Include="..\App1\App1.csproj" LayoutDir="App1" />
    <MsixContent Include="config.json" PackagePath="Assets\config.json" />
  </ItemGroup>
</Project>

Pipeline

BuildMsix orchestrator with a conditional pipeline:

Default (CLI/CI): Publish -> Merge -> Validate -> CopyAssets -> ResourceIndex -> Pack -> Sign

VS dev-loop (layout mode): Publish -> Merge -> Validate -> CopyAssets -> ResourceIndex -> DeployLayout (skips Pack/Sign)

#	Target	Description	Backed by
1	PublishToLayout	Publishes each ProjectReference with LayoutDir	dotnet publish
2	MergeAppxManifest	Multi-section fragment merge + version/arch stamping	MergeAppxFragments task
3	ValidateAppxManifest	XML well-formedness + required elements + duplicate IDs	ValidateAppxManifest task
4	CopyMsixAssets	Images + MsixContent items	MSBuild Copy
5	GenerateResourceIndex	MakePri.exe for .resw (auto/true/false)	WinAppSdkGetSdkFileFullPath + MakePri
6	PackMsix	Packs the layout into the .msix	WinAppSdkMakeAppxPack
7	SignMsix	Optional signing (+ timestamp / Azure)	WinAppSdkSignAppxPackage

Plus opt-in targets: CleanMsixLayout, InstallMsix, RegisterMsixLayout, UninstallMsix

Build tooling (Microsoft.Windows.SDK.BuildTools.MSIX)

The SDK uses the package's compiled tasks (namespace Microsoft.Build.Msix):

• WinAppSdkGetSdkFileFullPath — locates MakeAppx / SignTool / MakePri in the installed Windows SDK
• WinAppSdkMakeAppxPack — packs the layout into the .msix from a generated [Files] mapping file
• WinAppSdkSignAppxPackage — signs the .msix, with timestamp and Azure Code Signing / Key Vault support

Integration (not bundled): the package is injected as a PackageReference from Sdk.props with GeneratePathProperty and ExcludeAssets="build;buildTransitive", so only the task assembly is used and the package's heavyweight WinAppSDK pipeline is not imported. It is restored automatically (consumers do not add it manually). VersionOverride is used under Central Package Management so no central PackageVersion entry is required, and the task assembly is resolved per runtime (net6.0 for Core, net472 for desktop MSBuild). A small RoslynCodeTaskFactory inline task resolves the latest installed Windows SDK version for TargetPlatformVersion (honoring MsixWindowsSdkVersion when set).

Key Features

• Compiled tasks (netstandard2.0) — MergeAppxFragments, ValidateAppxManifest; SDK-tool discovery, packing, and signing come from the Microsoft.Windows.SDK.BuildTools.MSIX package
• Multi-section fragment merge — 4 manifest markers (Applications, Capabilities, Extensions, Dependencies)
• Manifest validation at build time — catches errors before install
• Version stamping via MsixPackageVersion (4-part numeric)
• MsixContent items for arbitrary content files
• Deploy-on-build — auto-registers layout when building in VS (layout mode skips Pack/Sign)
• VS Property Page — XAML Rule file with 10 properties across 4 categories (no VSIX needed)
• Clean integration — unregisters package + removes layout on clean
• 21 configurable properties (incl. MsixSdkBuildToolsVersion, MsixWindowsSdkVersion, MsixHashAlgorithmId)

What's Included

SDK Project (src/MsixPackaging/)

• Microsoft.Build.MsixPackaging.csproj — netstandard2.0, follows Artifacts pattern
• Tasks/ — 2 compiled MSBuild tasks (MergeAppxFragments, ValidateAppxManifest)
• Sdk/Sdk.props — NoTargets import, property defaults, build-tools package injection, VS property page
• Sdk/Sdk.targets — BuildMsix orchestrator + targets, using the build-tools package tasks
• Sdk/Microsoft.Build.MsixPackaging.PropertyPage.xaml — VS Project Properties page
• build/ — .props/.targets for traditional NuGet package consumption
• version.json (1.0), README.md

Unit Tests (src/MsixPackaging.UnitTests/)

• 14 tests across net472, net8.0, net9.0, net10.0
• MergeAppxFragmentsTests — version validation, fragment detection, attribute patching, indentation
• ValidateAppxManifestTests — valid manifest, missing elements, duplicate IDs, malformed XML, invalid version

Sample (samples/MsixPackaging/)

• SampleConsoleApp/ — trivial console app with AppxFragment.xml and MsixImages/
• SamplePackaging.msbuildproj — consumes the SDK from the source tree (builds a real .msix)
• Package.base.appxmanifest — minimal manifest template

Repo Conventions

• Naming — package Microsoft.Build.MsixPackaging, task namespace Microsoft.Build.MsixPackaging.Tasks
• SDK tool discovery / pack / sign — Microsoft.Windows.SDK.BuildTools.MSIX tasks
• Package versions — Central Package Management
• NoTargets version — from global.json msbuild-sdks
• Signing — FilesToSign (Authenticode + StrongName) for the task DLL
• Versioning — Nerdbank.GitVersioning (1.0)
• Task packaging — BuildOutputTargetFolder=build\ (Artifacts pattern)

Testing

• dotnet build --no-incremental — SDK compiles with 0 warnings, 0 errors (StyleCop clean)
• dotnet test — 14/14 tests pass across all 4 TFMs
• Sample builds end-to-end and produces a valid .msix (publish -> merge -> validate -> copy -> pack)