jasonrowe/windows-xaml-developer

Windows XAML Developer

Overview

This skill provides best practices, architectural patterns, and library recommendations for building high-quality Windows desktop applications using XAML-based frameworks (WinUI 3 and WPF). It emphasizes the Model-View-ViewModel (MVVM) pattern, Dependency Injection (DI), and modern C# features.

When to Use

• When generating code for Windows desktop applications (WinUI 3, WPF, UWP).
• When structuring a new Windows XAML project.
• When implementing the MVVM pattern.
• When troubleshooting XAML binding or UI responsiveness issues.

Core Principles

1. MVVM First: Always separate UI logic (View) from business logic (ViewModel). Avoid code-behind (.xaml.cs) except for pure UI concerns (e.g., window manipulation).
2. Dependency Injection: Use DI to manage services and ViewModels. Avoid static singletons for testability.
3. Responsive UI: Never block the UI thread. Use async/await for I/O and heavy computations.
4. Modern Tooling: Leverage Roslyn source generators (e.g., CommunityToolkit.Mvvm) to reduce boilerplate.
5. Build Integrity: When refactoring code into Shared Projects or Class Libraries, ALWAYS:
   • Update the .csproj of the consumer projects to exclude the source files if they were previously included via wildcards (e.g., <Compile Remove="SharedLib\**" />).
   • Run dotnet clean followed by dotnet build on the entire solution to ensure no stale artifacts or duplicate attribute errors remain.

Recommended Tech Stack

Frameworks

• Primary: WinUI 3 (Windows App SDK) - The modern, native UI stack for Windows. Best for new applications.
• Secondary: WPF (.NET 8/9) - Mature, stable ecosystem. Best for complex enterprise apps or when specific third-party controls are needed.

Essential Libraries

| Category | Library | Usage | | :--- | :--- | :--- | | MVVM | CommunityToolkit.Mvvm | Standard implementation for ObservableObject, RelayCommand, and Messenger. | | Dependency Injection | Microsoft.Extensions.DependencyInjection | Industry-standard DI container. | | Hosting/Lifecycle | Microsoft.Extensions.Hosting | Application bootstrap, logging, and configuration. | | WPF UI Library | MaterialDesignInXamlToolkit or MahApps.Metro | (WPF Only) Modern styling and controls. | | WinUI Helpers | CommunityToolkit.WinUI | Additional controls, helpers, and extensions for WinUI 3. |

Project Structure

Organize the solution to enforce strict separation of concerns:

MyWindowsApp/
├── App.xaml                 # Application entry & DI composition root
├── Views/                   # XAML Windows, Pages, and UserControls
├── ViewModels/              # C# ViewModels (one per View)
├── Models/                  # Domain entities and data structures
├── Services/                # Business logic and data access interfaces/implementations
├── Converters/              # IValueConverter implementations
└── Assets/                  # Images, fonts, and resources