Implementing Cross-Platform In-App Billing in .NET MAUI Applications

With the discontinuation of the popular InAppBillingPlugin, many .NET MAUI developers have been looking for guidance on implementing in-app purchases in their applications. Today, we’re sharing a comprehensive sample that demonstrates how to implement cross-platform billing for Android, iOS, Mac Catalyst, and Windows using platform-specific APIs with a unified interface.

The BillingService Sample

Our new BillingService sample shows you how to integrate platform-specific billing systems into your .NET MAUI applications while maintaining clean, maintainable code through dependency injection and the MVVM pattern. The sample includes complete implementations for:

Android: Google Play Billing Client v7
iOS & Mac Catalyst: StoreKit
Windows: Microsoft Store APIs

BillingService Demo showing product listings with purchase buttons on Android

Architecture Overview

The sample demonstrates several important architectural patterns for cross-platform development:

Unified Interface

At the core of the implementation is a clean IBillingService interface that abstracts platform-specific billing operations:

public interface IBillingService
{
    Task<bool> InitializeAsync();
    Task<IEnumerable<Product>> GetProductsAsync();
    Task<PurchaseResult> PurchaseAsync(string productId);
    Task<bool> RestorePurchasesAsync();
    bool IsProductOwned(string productId);
}

Platform-Specific Implementations

Each platform has its own implementation file using conditional compilation:

BillingService.Android.cs – Google Play Billing integration
BillingService.iOS.cs – StoreKit implementation (shared between iOS and Mac Catalyst)
BillingService.Windows.cs – Microsoft Store integration

The project file uses conditional compilation directives to include the appropriate implementation for each target platform, while iOS and Mac Catalyst share a single implementation since they both use identical StoreKit 1 APIs.

Dependency Injection

The billing service is registered in MauiProgram.cs and automatically resolves to the correct platform-specific implementation at runtime:

builder.Services.AddSingleton<IBillingService, Services.BillingService>();
builder.Services.AddTransient<ProductsViewModel>();

A Note on StoreKit Implementation

The current iOS and Mac Catalyst implementation uses StoreKit 1, which continues to work on all current iOS versions, including iOS 18, 26, and beyond. At WWDC 2024, Apple announced the deprecation of StoreKit 1 in favor of StoreKit 2, which offers enhanced features and modern Swift-first APIs with async/await support. While StoreKit 1 remains functional for existing implementations, Apple has indicated that future enhancements and new features will be exclusive to StoreKit 2.

This sample provides a production-ready implementation you can use in your apps today. We are still working on Swift interop for .NET and plan to update this sample once full StoreKit 2 support is available in .NET for iOS. The migration to StoreKit 2 will bring improvements like better transaction handling, enhanced subscription management, and modern async patterns, but your apps using StoreKit 1 will continue to function properly in the meantime.

Important

For production applications, you should implement server-side purchase validation and receipt verification to ensure security and prevent fraud. This sample focuses on the client-side implementation patterns.

Getting Started

To explore the sample and see how each platform implements billing:

Browse the complete source code in the .NET MAUI samples repository
Check out the online samples browser to see the sample in action
Clone the repository and run the sample on your development machine

The sample includes detailed README documentation with platform-specific setup instructions for Google Play Console, App Store Connect, and Microsoft Partner Center.