Platform-Specific Code in .NET MAUI

 In .NET MAUI, you can write platform-specific code using several approaches:

1. Using #if compiler directives

2. Using Dependency Injection (DI) with platform implementations

3. Using partial classes and platform folders

Here's a complete example using all three approaches for a feature that displays the current device's platform name.

Approach 1: Using Compiler Directives (#if)

csharp

public string GetPlatformName()
{
    string platform;
    
#if ANDROID
    platform = "Android";
#elif IOS
    platform = "iOS";
#elif MACCATALYST
    platform = "Mac Catalyst";
#elif WINDOWS
    platform = "Windows";
#else
    platform = "Unknown";
#endif

    return platform;
}

Approach 2: Using Dependency Injection (Recommended)

1. Create an Interface

csharp

public interface IDeviceService
{
    string GetPlatformName();
}

2. Implement Platform-Specific Services

Android Implementation (Platforms/Android/DeviceService.android.cs):

csharp

using YourApp.Platforms.Android;

namespace YourApp.Services
{
    public class DeviceService : IDeviceService
    {
        public string GetPlatformName() => "Android";
    }
}

iOS Implementation (Platforms/iOS/DeviceService.ios.cs):

csharp

using YourApp.Platforms.iOS;

namespace YourApp.Services
{
    public class DeviceService : IDeviceService
    {
        public string GetPlatformName() => "iOS";
    }
}

3. Register the Service in MauiProgram.cs

csharp

public static class MauiProgram
{
    public static MauiApp CreateMauiApp()
    {
        var builder = MauiApp.CreateBuilder();
        builder
            .UseMauiApp<App>()
            .ConfigureFonts(fonts =>
            {
                fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
            });

#if ANDROID
        builder.Services.AddSingleton<IDeviceService, Platforms.Android.DeviceService>();
#elif IOS
        builder.Services.AddSingleton<IDeviceService, Platforms.iOS.DeviceService>();
#endif

        return builder.Build();
    }
}

4. Use the Service in Your Code

csharp

public partial class MainPage : ContentPage
{
    private readonly IDeviceService _deviceService;
    
    public MainPage(IDeviceService deviceService)
    {
        InitializeComponent();
        _deviceService = deviceService;
        
        var platformName = _deviceService.GetPlatformName();
        PlatformLabel.Text = $"Running on: {platformName}";
    }
}

Approach 3: Using Partial Classes and Platform Folders

1. Create a Partial Class in Shared Project

csharp

public partial class DeviceInfo
{
    public partial string GetPlatformName();
}

2. Implement Platform-Specific Parts

Android Implementation (Platforms/Android/DeviceInfo.android.cs):

csharp

public partial class DeviceInfo
{
    public partial string GetPlatformName() => "Android";
}

iOS Implementation (Platforms/iOS/DeviceInfo.ios.cs):

csharp

public partial class DeviceInfo
{
    public partial string GetPlatformName() => "iOS";
}

3. Use the Class

csharp

var deviceInfo = new DeviceInfo();
var platform = deviceInfo.GetPlatformName();

Complete Example with Dependency Injection (Recommended)

Here's a complete end-to-end example using the DI approach:

1. Create a new MAUI project

2. Add IPlatformInfoService.cs:

csharp

public interface IPlatformInfoService
{
    string GetPlatformName();
    string GetPlatformVersion();
}

3. Add Android implementation (Platforms/Android/PlatformInfoService.cs):

csharp

using Android.OS;

public class PlatformInfoService : IPlatformInfoService
{
    public string GetPlatformName() => "Android";
    
    public string GetPlatformVersion()
    {
        return Build.VERSION.Release;
    }
}

4. Add iOS implementation (Platforms/iOS/PlatformInfoService.cs):

csharp

using UIKit;

public class PlatformInfoService : IPlatformInfoService
{
    public string GetPlatformName() => "iOS";
    
    public string GetPlatformVersion()
    {
        return UIDevice.CurrentDevice.SystemVersion;
    }
}

5. Register services in MauiProgram.cs:

csharp

var builder = MauiApp.CreateBuilder();
builder
    .UseMauiApp<App>()
    .ConfigureFonts(fonts => { /* font config */ });

// Register platform-specific services
#if ANDROID
builder.Services.AddSingleton<IPlatformInfoService, Platforms.Android.PlatformInfoService>();
#elif IOS
builder.Services.AddSingleton<IPlatformInfoService, Platforms.iOS.PlatformInfoService>();
#endif

// Register MainPage with dependency
builder.Services.AddTransient<MainPage>();

return builder.Build();

6. Use in MainPage.xaml.cs:

csharp

public partial class MainPage : ContentPage
{
    public MainPage(IPlatformInfoService platformInfo)
    {
        InitializeComponent();
        
        PlatformLabel.Text = $"Running on: {platformInfo.GetPlatformName()}";
        VersionLabel.Text = $"Version: {platformInfo.GetPlatformVersion()}";
    }
}

7. Update MainPage.xaml:

xml

<VerticalStackLayout>
    <Label x:Name="PlatformLabel" FontSize="24" HorizontalOptions="Center"/>
    <Label x:Name="VersionLabel" FontSize="18" HorizontalOptions="Center"/>
</VerticalStackLayout>

This example shows the recommended way to handle platform-specific code in MAUI using dependency injection, which makes your code more testable and maintainable. The compiler will automatically include only the appropriate platform implementation when building for each target.