WinUI 3 Line-of-Business Sample Hub

Five self-contained WinUI 3 (Windows App SDK) desktop samples demonstrating common line-of-business patterns. Each sample is an independent, buildable Visual Studio solution. They are linked from the documentation at learn.microsoft.com/windows/apps/get-started/line-of-business/.

Samples

#	Folder	Demonstrates
1	WinUI-LOB-Samples/01-TabularData	ItemsView + DataTemplate card layout and a Community Toolkit DataGrid with sortable columns
2	WinUI-LOB-Samples/02-ValidatedForm	Input validation with ObservableValidator ([Required], [EmailAddress]), per-keystroke validation, inline errors, Save gated on HasErrors
3	WinUI-LOB-Samples/03-DatabaseAccess	EF Core + SQLite task tracker, all data access async and off the UI thread
4	WinUI-LOB-Samples/04-DesignShowcase	NavigationView, Mica backdrop, compact/normal density toggle, light/dark theme toggle, summary card grid
5	WinUI-LOB-Samples/05-LocalAI	Local AI on a Copilot+ PC — on-device support-ticket triage (summarize + categorize) with the Phi Silica language model via Microsoft.Windows.AI.Text.LanguageModel; no data leaves the device

Screenshots

Sample	Screenshot
1 — TabularData (cards)
1 — TabularData (DataGrid, sorted)
2 — ValidatedForm (invalid email, Save disabled)
3 — DatabaseAccess (task tracker)
4 — DesignShowcase (dashboard + Mica)
5 — LocalAI (on-device triage, experimental channel)
5 — LocalAI (graceful degradation when the LAF gate blocks generation on the stable channel)

Shared conventions (all samples)

• WinUI 3 desktop, Windows App SDK 2.3.1 (stable channel), C# only, net10.0-windows.
• MVVM throughout — ViewModels derive from ObservableObject / ObservableValidator (CommunityToolkit.Mvvm).
• x:Bind for all data binding (never Binding — see the DataGrid exception below).
• ItemsView for all collection UI (never ListView).
• Microsoft.UI.Xaml.* only — no UWP Windows.UI.Xaml.*, ApplicationView, CoreWindow, or CoreApplication.
• System theme brushes only — no hardcoded colors.
• All data loading is async; EF Core queries and on-device model calls never run on the UI thread.
• No connection strings or credentials in source; the SQLite path is built at runtime from LocalApplicationData.

Building & running

Each sample requires .NET SDK 10.0.302+, Windows App SDK, Developer Mode enabled, and the winapp CLI. From a sample's project folder:

dotnet build
winapp run          # launch the packaged app (do not run the .exe directly)

Every sample builds with zero errors and zero warnings and has been launched and validated.

Key findings (SME-relevant discoveries)

These are the "known unknowns" that were resolved while building the samples — the docs should reflect these exact values:

1. Community Toolkit DataGrid NuGet package name (Sample 1). The intuitive/guessed name CommunityToolkit.WinUI.Controls.DataGrid does not exist on NuGet. The DataGrid has not migrated to the 8.x CommunityToolkit.WinUI.Controls.* segmented naming. The correct, current package is:

   CommunityToolkit.WinUI.UI.Controls.DataGrid   (v7.1.2)
   xmlns: using:CommunityToolkit.WinUI.UI.Controls
   

   It requires merging ms-appx:///CommunityToolkit.WinUI.UI.Controls.DataGrid/Themes/Generic.xaml into App.xaml.

2. DataGrid columns require {Binding}, not {x:Bind} (Sample 1). DataGridBoundColumn.Binding is typed as a classic Binding; the framework does not accept x:Bind there. This is the one sanctioned exception to the "always x:Bind" rule — every other binding in the samples uses x:Bind.

3. Compact-density resource dictionary URI (Sample 4). The resource dictionary that resolves at runtime on Windows App SDK 2.3.1 is:

   ms-appx:///Microsoft.UI.Xaml/DensityStyles/Compact.xaml
   

   Toggle density by adding/removing a ResourceDictionary { Source = <that URI> } on the root element's Resources.MergedDictionaries — it must be merged after XamlControlsResources.

4. Phi Silica API namespace (Sample 5). The current, verified local-AI API is Microsoft.Windows.AI.Text.LanguageModel (with the readiness enum Microsoft.Windows.AI.AIFeatureReadyState). The older Microsoft.Windows.AI.Generative.* namespace seen in some articles — and in this repo's own docs/ai-for-lob-apps.md — is outdated; that doc needs updating (see TODOs). Canonical call sequence:

   var state = LanguageModel.GetReadyState();          // AIFeatureReadyState
   if (state == AIFeatureReadyState.NotReady) await LanguageModel.EnsureReadyAsync();
   var model = await LanguageModel.CreateAsync();
   var result = await model.GenerateResponseAsync(prompt);   // check result.Status == Complete

   Requires the restricted capability systemAIModels (with the rescap/systemai manifest namespace) — the dotnet new winui template already declares it.

5. Phi Silica is a Limited Access Feature (LAF) on the stable channel (Sample 5). ⚠️ On stable Windows App SDK 2.3.1, GenerateResponseAsync throws "Access is denied. Limited Access Feature is not available: com.microsoft.windows.ai.languagemodel. Status: 3" for a locally dev-registered, unsigned package — even though GetReadyState() returns Ready, the systemAIModels capability is granted, and the privacy consent is allowed. TryUnlockFeature with the machine LAF token returns Unavailable because the token is bound to a Microsoft-issued per-package identity, which a sample can't obtain. The official Windows AI troubleshooting guide confirms this and recommends the experimental channel, which does not require a LAF token. Verified on this machine: switching to Microsoft.WindowsAppSDK 2.2.2-experimental9 makes on-device generation succeed end-to-end (see the 05-LocalAI-experimental screenshot). The sample ships on stable per the shared convention and degrades gracefully — it detects the gate, shows an explanatory InfoBar, and disables the triage button rather than surfacing a raw error.

Open TODOs / SME follow-ups

• Build toolchain: net10.0 requires MSBuild 18+. Visual Studio 2022's bundled MSBuild (17.14) cannot build these projects, so each sample pins the SDK via global.json (10.0.302) and builds through the dotnet CLI. Ensure the team's standard build host / CI uses a Visual Studio version with MSBuild 18, or standardize on dotnet build. The global.json files can be relaxed once that is confirmed.
• Sample 3 – schema evolution: uses EnsureCreatedAsync() (does not support schema changes). Switch to EF Core migrations for a production app.
• Sample 3 – persistence layer: no edit/delete-task UI yet (spec covered add + complete only).
• Sample 2 – Save() is a stub (shows an InfoBar and resets the form); wire it to a real service layer for an actual LOB app.
• Sample 3 – supply chain: the transitive SQLitePCLRaw.lib.e_sqlite3 2.1.11 carried CVE-2025-6965; pinned SQLitePCLRaw.bundle_e_sqlite3 2.1.12 to stay clean. Bump when EF Core ships a newer transitive default.
• Sample 5 – local AI runtime gate (needs SME/environment decision). On-device Phi Silica generation is blocked on the stable channel by the Limited Access Feature gate (see Key Finding 5). Options for the docs: (a) ship on stable with graceful degradation as done here and document that end-to-end generation requires either a Microsoft-issued LAF token or the experimental channel; or (b) target the experimental channel for the live-AI walkthrough (note: ItemsView/ItemContainer are marked evaluation-only there and emit CS8305, so it can't hit zero warnings without <NoWarn>). SME to confirm the intended guidance for readers.
• Sample 5 – SDK pin divergence. This machine only has .NET SDK 10.0.300-preview.0.26177.108 installed (not 10.0.302), so 05-LocalAI/.../global.json pins that preview to build and run locally. Normalize to 10.0.302 (matching Samples 1–4) on a host that has it installed.
• Sample 5 – docs/ai-for-lob-apps.md updated. The Phi Silica section now uses the correct Microsoft.Windows.AI.Text.LanguageModel API (was the outdated Microsoft.Windows.AI.Generative) and documents the LAF gate / channel guidance. SME to review the wording.