.NET MAUI Cross-Platform App Prompt for Shared UI and Native APIs

What this prompt does

This prompt builds a .NET MAUI cross-platform application for an [app_purpose] targeting [platforms]. It organizes the project with an [architecture_pattern] and Shell navigation, defines routes for [screens], creates [shared_pages] shared XAML pages that adapt across phone, tablet, and desktop using OnPlatform and OnIdiom, and implements [platform_features] through partial classes and conditional compilation. It also sets up an offline-first data layer with [local_storage] and native API access for [native_apis].

The structure works because one codebase across iOS, Android, and desktop only stays maintainable if the platform seams are deliberate. The prompt establishes where OnPlatform divergence and dependency-injection abstractions matter most, sets up Shell flyout, tab, and modal navigation for [menu_items], [tab_items], and [modal_pages], and includes a testing step with [test_approach]. Offline-first caching that syncs when online is treated as a first-class concern rather than bolted on later.

When to use it

• A client needs one codebase across [platforms] instead of separate native apps
• You are planning Shell navigation and routes for [screens] before building
• You need shared XAML that adapts across form factors via OnPlatform and OnIdiom
• You need platform-specific features like [platform_features] abstracted cleanly
• You want an offline-first data layer with [local_storage] that syncs when connectivity returns
• You need native APIs such as [native_apis] integrated through proper handlers

Example output

Expect a project plan and code: an MVVM-structured solution with Shell routes, shared XAML pages using OnPlatform and OnIdiom for responsive layout, partial-class abstractions for platform-specific features, an offline-first data layer with local caching and sync logic, Shell navigation configured for flyout, tab, and modal pages, DI registration with platform-specific implementations, native-API integration via handlers or the Community Toolkit, and unit and UI test setup.

Pro tips

• Name your [platforms] precisely, since Windows desktop and mobile differ enough that OnIdiom and OnPlatform branches need real thought, not copy-paste
• Keep [platform_features] behind an interface so ViewModels stay testable and platform code lives only in the partial-class implementations
• Design the offline-first layer around conflict resolution early; deciding how [local_storage] reconciles with the server after reconnect is harder to retrofit
• Register [di_services] with platform-specific implementations so the same ViewModel runs everywhere while the concrete service swaps per platform
• Use the Community Toolkit for common [native_apis] before writing custom handlers, since it covers camera, geolocation, and notifications already
• Treat UI tests with [test_approach] as a smoke layer; they are slower and flakier than ViewModel unit tests, so put most assertions in the latter
• Map your [screens] to Shell routes early so deep linking and back-navigation behave consistently rather than being patched in later
• Test responsive layouts on a real tablet and desktop, not just a phone emulator, since OnIdiom branches are easy to get subtly wrong across form factors