Platform Invoke in .NET MAUI

Two approaches exist for invoking platform-specific APIs from shared code.

1. Conditional Compilation

Use preprocessor directives for small, inline platform code:

public string GetDeviceName() { #if ANDROID return Android.OS.Build.Model; #elif IOS || MACCATALYST return UIKit.UIDevice.CurrentDevice.Name; #elif WINDOWS return Windows.Security.ExchangeActiveSyncProvisioning .EasClientDeviceInformation().FriendlyName; #else return "Unknown"; #endif }

Best for: one-off calls, quick checks, small blocks. Avoid for complex logic—use partial classes instead.

2. Partial Classes (Preferred)

Split a service into a cross-platform definition and per-platform implementations.

Cross-platform definition

Services/DeviceOrientationService.cs :

namespace MyApp.Services;

public partial class DeviceOrientationService { public partial DeviceOrientation GetOrientation(); }

public enum DeviceOrientation { Undefined, Portrait, Landscape }

Platform implementations

Platforms/Android/Services/DeviceOrientationService.cs :

namespace MyApp.Services;

public partial class DeviceOrientationService { public partial DeviceOrientation GetOrientation() { var activity = Platform.CurrentActivity ?? throw new InvalidOperationException("No current activity."); var rotation = activity.WindowManager?.DefaultDisplay?.Rotation; return rotation is SurfaceOrientation.Rotation90 or SurfaceOrientation.Rotation270 ? DeviceOrientation.Landscape : DeviceOrientation.Portrait; } }

Platforms/iOS/Services/DeviceOrientationService.cs :

namespace MyApp.Services;

public partial class DeviceOrientationService { public partial DeviceOrientation GetOrientation() { var orientation = UIKit.UIDevice.CurrentDevice.Orientation; return orientation is UIKit.UIDeviceOrientation.LandscapeLeft or UIKit.UIDeviceOrientation.LandscapeRight ? DeviceOrientation.Landscape : DeviceOrientation.Portrait; } }

Key rules

• Same namespace across all partial files.

• The build system auto-includes only the file matching the target platform from Platforms/{Platform}/ .

• No #if needed—MSBuild handles it.

Multi-Targeting Configuration

The default .csproj already multi-targets. To add custom file-based patterns:

<!-- Include files matching *.android.cs only for Android --> <ItemGroup Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'"> <Compile Include="***.android.cs" /> </ItemGroup>

You can also use folder-based conventions beyond Platforms/ :

<ItemGroup Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'"> <Compile Include="iOS***.cs" /> </ItemGroup>

Dependency Injection Registration

Register platform-specific implementations in MauiProgram.cs :

public static MauiApp CreateMauiApp() { var builder = MauiApp.CreateBuilder(); builder.UseMauiApp<App>();

// Interface-based (recommended for testability)
builder.Services.AddSingleton<IDeviceOrientationService, DeviceOrientationService>();

// Platform-specific registrations when implementations differ by type

#if ANDROID builder.Services.AddSingleton<IPlatformNotifier, AndroidNotifier>(); #elif IOS || MACCATALYST builder.Services.AddSingleton<IPlatformNotifier, AppleNotifier>(); #elif WINDOWS builder.Services.AddSingleton<IPlatformNotifier, WindowsNotifier>(); #endif

return builder.Build();

}

Prefer interfaces (IDeviceOrientationService ) so shared code depends on abstractions, enabling unit testing with mocks.

Android Java Interop Basics

Access Android APIs directly via C# bindings in the Android.* namespaces:

// Get a system service var connectivityManager = (Android.Net.ConnectivityManager) Platform.CurrentActivity! .GetSystemService(Android.Content.Context.ConnectivityService)!;

// Check network var network = connectivityManager.ActiveNetwork; var capabilities = connectivityManager.GetNetworkCapabilities(network); bool hasWifi = capabilities?.HasTransport( Android.Net.TransportType.Wifi) ?? false;

For APIs without existing bindings, use Java Native Interface via Java.Interop or create an Android Binding Library.

Quick Reference

Approach When to use

#if ANDROID

Small inline checks, 1–5 lines

Partial classes Services, complex logic, testable code

Interface + DI Swappable implementations, unit testing

Custom file patterns Teams preferring *.android.cs naming