.NET MAUI

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Advanced & Enterprise Advanced Data Binding & Collections App Lifecycle & Windows Best Practices & Architecture Concurrency & Threading Controls & Views Data Binding & MVVM Dependency Injection & Services Desktop - WinUI & Mac Catalyst Device Features & Essentials Fonts, Icons & Media Forms, Input & Validation Fundamentals & Architecture Gestures & Animations Graphics & Drawing Local Storage & Data Maps & Location Migration from Xamarin.Forms Native Interop & Libraries Networking & APIs

.NET MAUI

Platform Integration & Handlers

Q: How do you write platform-specific code in shared files?

Use conditional compilation with platform symbols (ANDROID, IOS, MACCATALYST, WINDOWS) inside shared code, or split logic into files under Platforms/ that compile only for their target. Conditional compilation is fine for small snippets; partial classes/interfaces are cleaner for larger differences.

Q: What is MAUI Essentials and what does it provide?

The former Xamarin.Essentials APIs are built into MAUI (Microsoft.Maui.Devices, .Storage, .Media, etc.). They give cross-platform access to device features—Geolocation, Connectivity, Preferences, SecureStorage, Battery, Sensors, Clipboard, Sharing—behind a unified API so you don't call native code directly for common tasks.

Q: How do you customize a control on a single platform using a handler?

Use PropertyMapper customization scoped by checking the view instance, or subclass the handler for that control and register it. AppendToMapping adds behavior after the default; ModifyMapping replaces a specific property's mapping. Guard native calls with platform #if.

Q: How do you access a native view from a MAUI control?

Through the control's Handler.PlatformView, cast to the native type for the current platform (guarded by #if). This lets you call native APIs the cross-platform surface doesn't expose. Access it after the handler is created (e.g., in HandlerChanged).

Q: How do you request runtime permissions in MAUI?

Use the Permissions API: check the status with CheckStatusAsync and request with RequestAsync for a permission type (e.g., LocationWhenInUse, Camera). Declare the permission in each platform manifest (AndroidManifest.xml, Info.plist). Handle Denied and Disabled states gracefully.

Q: How do you create a custom handler for a brand-new cross-platform control?

Define an interface (IMyControl : IView), a cross-platform control implementing it, and a partial handler with platform-specific CreatePlatformView plus a PropertyMapper mapping your properties to native calls. Register the handler in MauiProgram via ConfigureMauiHandlers.

Q: How do you invoke platform APIs that have no MAUI abstraction, cleanly?

Define a shared interface, implement it per platform (Platforms folder partial classes), and register in DI. This keeps native calls isolated and testable via the interface, unlike scattering #if throughout business logic. It's the recommended pattern for features like biometric auth or platform-specific storage.

7 question(s)

How do you write platform-specific code in shared files?

Beginner

Use conditional compilation with platform symbols (ANDROID, IOS, MACCATALYST, WINDOWS) inside shared code, or split logic into files under Platforms/ that compile only for their target. Conditional compilation is fine for small snippets; partial classes/interfaces are cleaner for larger differences.

string GetPlatformName()
{
#if ANDROID
    return "Android";
#elif IOS
    return "iOS";
#else
    return "Other";
#endif
}

Real-world example A quick analytics tag reports the OS name using a small #if block rather than a whole new abstraction.

Common follow-ups: When prefer partial classes over #if? | What symbols are available?

Multi-targeting Conditional Compilation Project Structure

What is MAUI Essentials and what does it provide?

Beginner

The former Xamarin.Essentials APIs are built into MAUI (Microsoft.Maui.Devices, .Storage, .Media, etc.). They give cross-platform access to device features—Geolocation, Connectivity, Preferences, SecureStorage, Battery, Sensors, Clipboard, Sharing—behind a unified API so you don't call native code directly for common tasks.

var location = await Geolocation.Default.GetLocationAsync();
bool online = Connectivity.Current.NetworkAccess == NetworkAccess.Internet;

Real-world example An app checks connectivity and reads GPS with two lines instead of separate Android and iOS location APIs.

Common follow-ups: Do Essentials need permissions? | Which namespace holds device APIs?

Device Features Permissions Platform Integration

How do you customize a control on a single platform using a handler?

Intermediate

Use PropertyMapper customization scoped by checking the view instance, or subclass the handler for that control and register it. AppendToMapping adds behavior after the default; ModifyMapping replaces a specific property's mapping. Guard native calls with platform #if.

#if IOS
Microsoft.Maui.Handlers.SwitchHandler.Mapper.AppendToMapping(
    "Tint", (h, v) => h.PlatformView.OnTintColor =
        UIKit.UIColor.SystemGreenColor);
#endif

Real-world example Product design wants iOS switches tinted brand-green; a single iOS-guarded mapper achieves it without touching Android.

Common follow-ups: AppendToMapping vs ModifyMapping? | How do you scope to one control instance?

Handlers Property Mapper Custom Controls

How do you access a native view from a MAUI control?

Intermediate

Through the control's Handler.PlatformView, cast to the native type for the current platform (guarded by #if). This lets you call native APIs the cross-platform surface doesn't expose. Access it after the handler is created (e.g., in HandlerChanged).

myEntry.HandlerChanged += (s, e) =>
{
#if ANDROID
    var native = (Android.Widget.EditText)myEntry.Handler.PlatformView;
    native.SetSelectAllOnFocus(true);
#endif
};

Real-world example A form selects all text when an Entry gains focus on Android by reaching the native EditText via the handler.

Common follow-ups: When is PlatformView available? | Why guard with #if?

Handlers Platform Integration Controls & Views

How do you request runtime permissions in MAUI?

Intermediate

Use the Permissions API: check the status with CheckStatusAsync and request with RequestAsync for a permission type (e.g., LocationWhenInUse, Camera). Declare the permission in each platform manifest (AndroidManifest.xml, Info.plist). Handle Denied and Disabled states gracefully.

var status = await Permissions.CheckStatusAsync<Permissions.Camera>();
if (status != PermissionStatus.Granted)
    status = await Permissions.RequestAsync<Permissions.Camera>();

Real-world example Before opening the camera, the app checks and requests camera permission, showing a rationale if the user previously denied it.

Common follow-ups: Where do you declare permissions per platform? | How do you handle a denied result?

Permissions Device Features Platform Integration

How do you create a custom handler for a brand-new cross-platform control?

Advanced

Define an interface (IMyControl : IView), a cross-platform control implementing it, and a partial handler with platform-specific CreatePlatformView plus a PropertyMapper mapping your properties to native calls. Register the handler in MauiProgram via ConfigureMauiHandlers.

public partial class VideoHandler : ViewHandler<IVideo, PlatformVideoView>
{
    public static IPropertyMapper<IVideo, VideoHandler> Mapper =
        new PropertyMapper<IVideo, VideoHandler>(ViewMapper)
        { [nameof(IVideo.Source)] = MapSource };

    protected override PlatformVideoView CreatePlatformView() => new(Context);
}

Real-world example A team wraps each platform's native video player in one cross-platform Video control with a custom handler.

Common follow-ups: How do you register a custom handler? | What is CreatePlatformView?

Handlers Custom Controls Platform Integration

How do you invoke platform APIs that have no MAUI abstraction, cleanly?

Advanced

Define a shared interface, implement it per platform (Platforms folder partial classes), and register in DI. This keeps native calls isolated and testable via the interface, unlike scattering #if throughout business logic. It's the recommended pattern for features like biometric auth or platform-specific storage.

public interface IBiometricAuth { Task<bool> AuthenticateAsync(string reason); }
// Platforms/iOS/BiometricAuth.cs -> LAContext
// Platforms/Android/BiometricAuth.cs -> BiometricPrompt
builder.Services.AddSingleton<IBiometricAuth, BiometricAuth>();

Real-world example Face ID and Android BiometricPrompt sit behind one IBiometricAuth so the login view model calls a single method.

Common follow-ups: Why an interface over #if? | How does this help testing?

Platform Integration Dependency Injection Custom Controls