Add Reactor (Microsoft.UI.Reactor) dotnet new templates by azchohfi · Pull Request #6620 · microsoft/WindowsAppSDK

azchohfi · 2026-07-15T03:06:13Z

Summary

Adds four Reactor (Microsoft.UI.Reactor) project templates to the existing Microsoft.WindowsAppSDK.WinUI.CSharp.Templates dotnet new pack, mirroring the WinUI templates from #6407 but for Reactor's declarative, pure-C# (no XAML) model.

Template	Short names	What it scaffolds
Reactor Blank App	`reactor`, `reactor-blank`	Minimal Hello-World Reactor app
Reactor MVU App	`reactor-mvu`	Model-View-Update counter using `UseReducer`
Reactor NavigationView App	`reactor-navview`	`NavigationView` shell with multiple pages
Reactor TabView App	`reactor-tabview`	`TabView` shell with multiple tabs

What changed

dev/Templates/templates.props — four new rows in the DotnetNewOnlyProjectTemplate slot (dotnet-new only, no VSIX). Reactor apps run unpackaged, so there is no Package.appxmanifest (RenameManifestFrom left unset). This reuses the repo's existing single-source-of-truth pack pipeline.
dev/Templates/Source/ProjectTemplates/Desktop/CSharp/Reactor* — the app sources: a shared ProjectTemplate.csproj (references Microsoft.UI.Reactor + Microsoft.WindowsAppSDK, WindowsAppSDKSelfContained, Debug-only Reactor devtools), a single-file App.cs per pattern, and Properties/launchSettings.json (default + Devtools F5 profiles).
dev/Templates/Dotnet/templates/reactor-* — the .template.config for each (template.json, dotnetcli.host.json, ide.host.json, icon.png). Defaults: Reactor 0.1.0-preview.12, Windows App SDK 2.1.3, net10.0; overridable via --reactor-version / --wasdk-version.
dev/Templates/Dotnet/README.md — documents the new Reactor templates.
dev/Templates/Dotnet/Test-DotnetNewTemplates.ps1 — adds the four to the scaffold/build validation loop.

Validation

Validated end-to-end against the live Microsoft.UI.Reactor 0.1.0-preview.12: dotnet pack → dotnet new install → all four register → dotnet new → dotnet build (Debug + Release) → dotnet run. All four launch cleanly, including the title-bar app-mark icon (which relies on the IconResolver fix from microsoft/microsoft-ui-reactor#855, shipped in preview.12).

A Microsoft employee must use /azp run to validate using the PR pipelines.

Adds four Reactor project templates to the Microsoft.WindowsAppSDK.WinUI.CSharp.Templates dotnet-new pack, mirroring the WinUI templates but for Microsoft.UI.Reactor (pure C#, no XAML): - Reactor Blank App (reactor, reactor-blank) - Reactor MVU App (reactor-mvu) - Reactor NavigationView (reactor-navview) - Reactor TabView App (reactor-tabview) Wired into dev/Templates/templates.props via the DotnetNewOnlyProjectTemplate slot (dotnet-new only, no VSIX, no manifest; Reactor apps run unpackaged). Each shares a common csproj referencing Microsoft.UI.Reactor + Microsoft.WindowsAppSDK, bundles the WinAppSDK runtime self-contained, and enables the Debug-only Reactor devtools surface. README and Test-DotnetNewTemplates.ps1 updated to document and validate the new templates. Validated end-to-end: pack -> install -> dotnet new -> build (Debug + Release) for all four templates. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

TitleBar(...).Icon(FontIcon(...)) threw System.ArgumentException (E_INVALIDARG) at runtime when Reactor set TitleBar.IconSource on Windows App SDK 2.1.3, so the scaffolded Blank, MVU, and TabView apps crashed on launch. The glyph was only a placeholder, so drop the icon; the title bar still shows the title text and all four templates now launch cleanly (validated with dotnet run). Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

microsoft/microsoft-ui-reactor#855 fixes the IconResolver FontSize=NaN crash (FontIcon in an IconSource slot without an explicit size threw ArgumentException from TitleBar.set_IconSource). That fix ships in Microsoft.UI.Reactor 0.1.0-preview.12, so restore the placeholder title-bar app-mark icon in the Blank, MVU, and TabView templates and bump the default reactorVersion 0.1.0-preview.11 -> 0.1.0-preview.12 across all four templates. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

azure-pipelines · 2026-07-15T03:06:22Z

Azure Pipelines: There may be pipelines that require an authorized user to comment /azp run to run.

azure-pipelines · 2026-07-15T05:01:58Z

Azure Pipelines: There may be pipelines that require an authorized user to comment /azp run to run.

azchohfi · 2026-07-23T21:09:05Z

/azp run

azure-pipelines · 2026-07-23T21:09:32Z

Azure Pipelines: Successfully started running 2 pipeline(s). 1 pipeline(s) were filtered out due to trigger conditions.

The template smoke-test stage installed only .NET SDK 8.0.x, so scaffolding and building the Reactor templates failed with NETSDK1045 (Reactor targets net10.0 and declares a [10.0,) sdk-version constraint). The WinUI templates auto-detect their TFM from the active SDK, so they built net8.0 and passed, masking the gap. Add a second UseDotNet@2 step (param reactorDotnetSdkVersion, default 10.0.x) to the shared Test-Stage template so the agent has the .NET 10 SDK. Verified locally that the WinUI templates still build cleanly on the .NET 10 SDK, so existing coverage is unaffected. Both the official and PR pipelines consume this shared stage. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

azchohfi · 2026-07-23T22:55:54Z

/azp run

azure-pipelines · 2026-07-23T22:56:17Z

Azure Pipelines: Successfully started running 2 pipeline(s). 1 pipeline(s) were filtered out due to trigger conditions.

DinahK-2SO · 2026-07-24T06:05:37Z

@@ -0,0 +1,18 @@
+{
+  "//": "Default F5 / `dotnet run` profiles for the scaffolded Reactor app.",


Why are we having these comments in launchsettings.json files? Some of these contents overlap with those in the package's README.

Can we remove them?

DinahK-2SO · 2026-07-24T06:09:05Z

+    <Platforms>x64;ARM64;x86</Platforms>
+    <UseWinUI>true</UseWinUI>
+    <!-- Reactor apps run unpackaged. -->
+    <WindowsPackageType>None</WindowsPackageType>


Why not make them packaged apps? Dotnet run supports packaged apps now.

@azchohfi You can reference the existing winui templates, when you launch them, there will be an app id.

For instance,

DinahK-2SO · 2026-07-24T06:19:05Z

@@ -0,0 +1,51 @@
+<Project Sdk="Microsoft.NET.Sdk">


Missing taskbar icons in all new templates.

DinahK-2SO · 2026-07-24T06:21:55Z

Should use the special icon for navigation view here.

DinahK-2SO · 2026-07-24T06:22:19Z

Should use the special icon for tab view here~

DinahK-2SO · 2026-07-24T06:23:41Z

+{
+    public override Element Render()
+    {
+        var (selectedIndex, setSelectedIndex) = UseState(0);


Hi @azchohfi, can we integrate the tabs into the title bar? That would be cleaner and save some vertical space.

You can reference the winui-tabview template about the config.

in contrast, the current reactor-tabview is stacking tabs below title bar:

DinahK-2SO · 2026-07-24T06:27:20Z

+  "identity": "Microsoft.WindowsAppSDK.Reactor.CSharp.BlankApp",
+  "groupIdentity": "Microsoft.WindowsAppSDK.Reactor.CSharp.BlankApp",
+  "name": "Reactor Blank App",
+  "shortName": [ "reactor", "reactor-blank" ],


Right now these new templates will be found by "dotnet new list reactor".

Can we also have some short names starts with "winui-"? like,

"shortName": [ "reactor", "reactor-blank", "winui-reactor" ]

so that our users can see there're new templates when they run "dotnet new list winui" command with the new package?

@azchohfi, @niels9001 , @Scottj1s , @beth-panx How do you like this suggestion?

azchohfi and others added 3 commits July 13, 2026 11:53

microsoft-github-policy-service Bot added the needs-triage label Jul 15, 2026

Merge branch 'main' into azchohfi-reactor-dotnet-new-templates

e31aed3

azchohfi marked this pull request as ready for review July 15, 2026 05:01

Merge branch 'main' into azchohfi-reactor-dotnet-new-templates

cc5a9b1

beth-panx requested review from DinahK-2SO and Scottj1s July 23, 2026 20:46

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		@@ -0,0 +1,18 @@
		{
		"//": "Default F5 / `dotnet run` profiles for the scaffolded Reactor app.",

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