WinUI 3 Solution Sample

This sample is a multi-project Visual Studio solution used to exercise winapp run solution mode — where you point winapp run at a .sln/.slnx (or a directory containing one) and it figures out which project to run.

What This Sample Shows

• A classic .sln (WinUISolution.sln) with three projects:
  • App — a packaged WinUI 3 desktop app (the runnable app).
  • App.Core — a WinUI 3 class library referenced by App that deliberately declares no <Platforms> (see below).
  • App.Tests — a test-shaped project that reproduces the shape found in real solutions like the WinUI Gallery and the AI Dev Gallery.
• winapp run auto-selecting the runnable App from the solution and skipping App.Core (a library) and App.Tests, with no ambiguity error.
• Explicit project selection via --project when you want a specific project.
• A multi-project arch regression guard: App references App.Core, which declares no <Platforms>. A global -p:Platform=<arch> would desynchronize the library's XAML/PRI output path from the app's lookup (MSB3030/PRI252), so a green build here proves winapp keeps the two consistent.

The projects

Project	Kind	Key markers
App	Packaged WinUI 3 app	OutputType=WinExe, UseWinUI=true, EnableMsixTooling=true, Package.appxmanifest, ProjectReference → App.Core
App.Core	WinUI 3 class library (arch regression guard)	UseWinUI=true, no <Platforms> (effective Platform AnyCPU), a Themes/Generic.xaml ResourceDictionary so the XAML compiler emits a .pri/.xbf
App.Tests	Test-shaped (skipped by auto-select)	OutputType=WinExe, <ProjectCapability Include="TestContainer" />, MSTest.TestFramework ref, IsTestProject deliberately NOT set

App.Core intentionally declares no <Platforms> (effective Platform AnyCPU). Because winapp only injects an explicit -p:Platform=<arch> when the target and its whole ProjectReference closure declare that arch, this sample builds with the architecture conveyed by -r win-<arch> alone — so the library's Generic.xbf/.pri and the consuming app agree on one output path. The solution maps App.Core to Any CPU for every configuration (the VS-canonical mapping for a no-<Platforms> library) so a plain dotnet build WinUISolution.sln -p:Platform=<arch> stays consistent too.

App.Tests intentionally does not set IsTestProject, so a naive check on that property (or on a .Tests name suffix) would miss it. winapp run classifies it from evaluated signals — the TestContainer capability and the MSTest package reference — which is the realistic gallery shape.

How winapp run picks the project

When given a solution (or a directory containing one), winapp run:

1. Lists the projects in the solution.
2. Classifies each as a runnable app, a library, or a test project (using evaluated OutputType, IsTestProject, TestContainer capability, and known test-framework package references).
3. Selects:
   • the single runnable app if there is exactly one, or
   • the single test project if there are no apps and exactly one test project, or
   • errors and lists the candidates if the choice is ambiguous — pass --project to disambiguate.

Building and Running

# Auto-select the runnable app from the solution and build + launch it.
winapp run WinUISolution.sln

# Same, but only build + register the debug identity without launching (no GUI).
winapp run WinUISolution.sln --no-launch

# Point at the directory instead of the .sln explicitly (directory mode finds the .sln).
winapp run .

# Explicitly select a specific project.
winapp run WinUISolution.sln --project App

# Build the whole solution with dotnet directly.
dotnet build WinUISolution.sln -c Debug -p:Platform=x64

Automated test

test.Tests.ps1 (Pester 5.x) validates solution mode end-to-end:

• Phase 1 copies the sources to a clean temp directory and runs winapp run WinUISolution.sln --no-launch, asserting the App project is auto-selected and built (no ambiguity error), then that --project App.Tests reaches the explicitly selected test project.
• Phase 2 restores and builds the existing solution to verify the committed sample still compiles.

Run it with:

.\scripts\test-samples.ps1 -Samples winui-solution