Plugin System in .NET MAUI Using MEF

In modern app development, extensibility is key. Whether you're building an enterprise solution, a white-labeled product, or an app that supports third-party integrations, a plugin-based architecture allows you to add features dynamically without modifying the core application.
In this guide, you'll learn how to implement a plugin system in .NET MAUI using the Managed Extensibility Framework (MEF). We'll cover:

• Why use a plugin system?

• Setting up MEF in .NET MAUI

• Defining plugin contracts

• Implementing and loading plugins dynamically

• Advanced techniques (metadata, hot-reloading, DI integration)

1. Why Use a Plugin System?

A plugin architecture provides several benefits:
✅ Modularity – Features are isolated, making the app easier to maintain.
✅ Extensibility – Third-party developers (or internal teams) can add functionality without modifying the core app.
✅ A/B Testing & Feature Flags – Enable/disable plugins at runtime.
✅ Dynamic Updates – Load new features without redeploying the entire app.
✅ White-Labeling – Customize app behavior per client by swapping plugins.

2. Project Setup

Solution Structure

For a clean architecture, we’ll structure our solution as follows:

1. MauiApp – The main .NET MAUI application.

2. PluginContracts (.NET Standard) – Defines interfaces for plugins.

3. SamplePlugin (.NET Standard) – A sample plugin implementation.

Install MEF

MEF (System.Composition) is the official Microsoft library for extensibility.

In all projects (MAUI, PluginContracts, SamplePlugin)

3. Defining the Plugin Contract

The PluginContracts project defines the interfaces that all plugins must implement.

IPlugin Interface

Optional: Metadata for Plugins

We can enrich plugins with metadata (e.g., version, author, dependencies).

4. Implementing a Plugin

Plugins must:

• Reference PluginContracts.

• Be decorated with [Export] for MEF discovery.

Example: HelloPlugin

Adding Metadata

5. Loading Plugins Dynamically

MEF scans assemblies for [Export] attributes and instantiates them.

PluginLoader Class

Handling MAUI-Specific Challenges

• iOS Restrictions: Dynamic loading is restricted; consider using Assembly.Load instead of LoadFrom.

• Android Assets: Plugins must be copied to a writable directory before loading.

6. Using Plugins in the MAUI App

Loading and Executing Plugins

7. Advanced Techniques

A. Metadata-Based Filtering

B. Hot-Reloading Plugins

• Watch a directory for new .dll files.

• Use AssemblyLoadContext for unloading (requires .NET 6+).

C. Dependency Injection (DI) Integration

D. Remote Plugins (Download & Load)

8. Security Considerations

🔒 Validate Plugins:

• Use strong-naming or code signing.

• Run plugins in a restricted AssemblyLoadContext.

🔒 Sandboxing:

• Consider running untrusted plugins in a separate process.

9. Deep Dive into Hot-Reloading Plugins

Hot-reloading plugins allows your .NET MAUI app to dynamically load, unload, and update plugins at runtime without restarting the application. This is especially useful for:

• Development efficiency (test plugins without full rebuilds)

• Live updates (deploy new plugin versions remotely)

• A/B testing (swap features dynamically)

9.1 How Hot-Reloading Works

To achieve hot-reloading, we need:
✅ File watcher – Monitor a directory for plugin changes.
✅ AssemblyLoadContext – Load/unload assemblies dynamically (.NET 6+).
✅ Dependency tracking – Ensure no memory leaks from unloaded plugins.

9.2 Implementing Hot-Reloading

Step 1: Set Up a File Watcher

Step 2: Use AssemblyLoadContext for Unloading

Step 3: Integrate with MEF

Step 4: Full Hot-Reload Flow

9.3 Handling Dependencies

Problem:

If a plugin depends on a shared library, unloading it may fail if other plugins use the same dependency.

Solution:

• Isolate dependencies per plugin using AssemblyLoadContext.

• Use AssemblyDependencyResolver (.NET Core 3.0+) to resolve private dependencies.

9.4 Testing Hot-Reloading

1. Run the MAUI app.

2. Modify a plugin DLL (e.g., update HelloPlugin.cs and rebuild).

3. Copy the new DLL to the watched plugins folder.

4. Observe logs – The app should detect changes and reload the plugin.

9.5 Limitations & Workarounds

Conclusion

By leveraging MEF, you can transform your .NET MAUI app into a modular, extensible platform that supports:

• Third-party plugins

• Dynamic feature loading

• A/B testing & white-labeling

This approach is ideal for enterprise apps, SaaS platforms, or apps requiring runtime customization.