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 sideloadable MSIX (single package or multi-architecture bundle) using per-project AppxFragment.xml manifest entries. Replaces WAP/DesktopBridge with a transparent, SDK-style workflow.

SDK-tool discovery, packing, signing, symbol packaging, and Store packaging 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 (opt-in stages no-op unless enabled):

Single package (default): Publish -> Merge -> Validate -> CopyAssets -> ResourceIndex -> Pack -> Symbol -> Sign -> AppInstaller

Bundle (MsixBundleEnabled): per-architecture Publish/Merge/Validate/CopyAssets/ResourceIndex/Pack -> makeappx bundle -> Symbol -> Sign -> AppInstaller -> StoreUpload

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

Target	Description	Backed by
PublishToLayout	Publishes each ProjectReference with LayoutDir (per-architecture RID in bundle mode)	dotnet publish
MergeAppxManifest	Multi-section fragment merge + version/arch stamping	MergeAppxFragments task
ValidateAppxManifest	XML well-formedness + required elements + duplicate IDs	ValidateAppxManifest task
CopyMsixAssets	Images + MsixContent items	MSBuild Copy
GenerateResourceIndex	MakePri.exe for .resw (auto/true/false)	WinAppSdkGetSdkFileFullPath + MakePri
PackMsix	Packs the layout into the .msix	WinAppSdkMakeAppxPack
BundleMsix	Builds each architecture and combines them into a .msixbundle	per-arch pack + makeappx bundle
GenerateMsixSymbolPackage	Produces a .msixsym from the layout PDBs	WinAppSdkGenerateAppxSymbolPackage
SignMsix	Signs the .msix/.msixbundle (cert file, test cert, timestamp, or Azure)	WinAppSdkSignAppxPackage (+ validation)
GenerateMsixAppInstaller	Writes an .appinstaller for sideload auto-update	direct XML generation
CreateMsixUpload	Wraps the bundle (and symbol) into a .msixupload	WinAppSdkCreateAppStoreContainer

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): SDK-tool discovery (WinAppSdkGetSdkFileFullPath), packing (WinAppSdkMakeAppxPack), signing (WinAppSdkSignAppxPackage), publisher/certificate validation (WinAppSdkValidatePublisherName, WinAppSdkValidateSigningCertificate), symbol packaging (WinAppSdkGenerateAppxSymbolPackage), and Store container creation (WinAppSdkCreateAppStoreContainer).

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 RoslynCodeTaskFactory inline task resolves the latest installed Windows SDK version for TargetPlatformVersion (honoring MsixWindowsSdkVersion when set).

Key Features

• 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
• Signing — certificate file, auto-generated test certificate (in-memory, matching the manifest Publisher), RFC 3161 timestamping, and Azure Code Signing / Azure Key Vault; the Publisher is validated against the certificate before signing
• Symbol package (.msixsym) for Partner Center crash analysis
• App Installer (.appinstaller) for sideload auto-update (references the bundle or the .msix)
• Multi-architecture bundle (.msixbundle) across MsixBundlePlatforms (e.g. x64|x86|arm64)
• Store upload (.msixupload) wrapping the bundle and symbol for Partner Center
• Deploy-on-build — auto-registers the layout when building in VS (layout mode skips Pack/Sign)
• VS Property Page — XAML Rule file across Package / Deployment / Signing / Bundle / Distribution / Resources categories (no VSIX needed)
• Clean integration — unregisters package + removes layout on clean

All signing, symbol, App Installer, bundle, and Store-upload features are opt-in and off by default; the default build produces a single unsigned .msix.

What's Included

SDK Project (src/MsixPackaging/)

• Microsoft.Build.MsixPackaging.csproj — netstandard2.0, follows the 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 and all targets, using the build-tools package tasks
• Sdk/Microsoft.Build.MsixPackaging.PropertyPage.xaml — VS Project Properties page
• Sdk/New-MsixTestCertificate.ps1 — generates an in-memory self-signed test certificate
• 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 (version/architecture), indentation
• ValidateAppxManifestTests — valid manifest, missing elements, duplicate IDs, malformed XML, invalid version

Sample (samples/MsixPackaging/)

• SampleConsoleApp/ — console app with AppxFragment.xml, MsixImages/, and <RuntimeIdentifiers> for bundling
• SamplePackaging.msbuildproj — consumes the SDK; the default build demonstrates test-certificate signing, the symbol package, and the App Installer, with the multi-architecture bundle and Store upload available via documented opt-in properties
• Package.base.appxmanifest — minimal manifest template

Repo Conventions

• Naming — package Microsoft.Build.MsixPackaging, task namespace Microsoft.Build.MsixPackaging.Tasks
• SDK tool discovery / pack / sign / symbol / upload — 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)

Notes

• Referenced apps must declare the bundle architectures in <RuntimeIdentifiers> so restore covers them; MsixStoreUploadEnabled requires a bundle.
• MsixToolArchitecture is a no-op (the build-tools package resolves tool architecture automatically); retained for backward compatibility.

Testing

• dotnet build --no-incremental — SDK compiles with 0 warnings, 0 errors (StyleCop clean) and packs (task DLL + Sdk/ content)
• dotnet test — 14/14 tests pass across all 4 TFMs
• Sample default build — signed .msix + .msixsym + .appinstaller
• Sample bundle build (x64|x86|arm64) — signed .msixbundle (all architectures) + .msixupload + .msixsym + .appinstaller