Extension Service

Overview

IExtensionService is the mechanism that allows any ExtendableViewModel to be augmented with additional behavior without modifying its source code.

At startup, each extension is registered in the DI container via the Extensions builder:

builder.Extensions.Register<IHomePage, MyHomePageExtension>();

When an ExtendableViewModel is initialized, it asks IExtensionService to resolve every IExtensionFor<TSelfInterface> registered for its type and calls Extend on each one. This keeps the view model itself clean while plugins and modules can freely add commands, tools, or other logic to it.

For a detailed walkthrough see Extendable View Model.

API

IExtensionService

Resolves and applies all registered IExtensionFor<TInterface> extensions to a given owner. Used internally by ExtendableViewModel to load extensions from the DI container.

Method	Return Type	Description
`Extend<TInterface>(TInterface owner, string ownerKey, CompositeDisposable ownerDisposable)`	`void`	Resolves all extensions for `TInterface` and applies them to the owner.

`IExtensionService.Extend`

Parameter	Type	Description
`owner`	`TInterface`	The target object to extend.
`ownerKey`	`string`	Key used to resolve keyed extensions from the DI container in addition to non-keyed ones.
`ownerDisposable`	`CompositeDisposable`	Disposable collection tied to the owner's lifetime. Extensions and their disposables are registered here.

The default implementation (ExtensionService) resolves both non-keyed (GetServices<IExtensionFor<TInterface>>()) and keyed (GetKeyedServices<IExtensionFor<TInterface>>(ownerKey)) extensions from the IServiceProvider. If an extension implements IDisposable, it is automatically added to ownerDisposable.

IExtensionFor<T>

Defines a contract for an extension that can be applied to a specific type T. This interface allows modular enhancements to be dynamically applied to existing objects.

Method	Return Type	Description
`Extend(T context, CompositeDisposable contextDispose)`	`void`	Applies the extension logic to the given context.

`IExtensionFor<T>.Extend`

Parameter	Type	Description
`context`	`T`	The target object to extend.
`contextDispose`	`CompositeDisposable`	Disposable collection, that disposed with context.

Last modified: 20 April 2026