Plugins.md

🧩 Plugins

⚡ TL;DR (quick version)
FusionCache supports extensibility via plugins: it is possible for example to listen to events and react in any way you want.

How to create a plugin

Simply write a class that implements the IFusionCachePlugin interface, which basically boils down to implement just the Start and Stop methods: from there you can setup your custom logic and do your thing.

Of course it can also accept its own set of options, typically modelled via IOptions<MyPluginType> and friends.

If you like there's a 🧩 complete sample available.

In time, the most useful plugins will be listed directly in the homepage.

How to use a plugin via DI

As explained in the Builder docs, we have 2 ways:

• register our plugin in the DI container (better before registering FusionCache itself) to respond to the IFusionCachePlugin service (either as singleton or transient, depending on the specific plugin) and tell FusionCache to use all registered plugins
• directly specify to use a plugin via an instance or a factory

The first approach looks like this:

services.AddTransient<IFusionCachePlugin, MyPlugin>();

services.AddFusionCache()
  .WithAllRegisteredPlugins()
;

The second approach looks like this:

services.AddFusionCache()
  .WithPlugin(new MyPlugin(...))
;

In both cases, when a FusionCache instance will be created by the DI container, the plugins will be added (and started) automatically.

Of course to be a better .NET citizen you can also define your own custom ext method (like AddMyFusionCachePlugin) and custom options:

services.AddMyFusionCachePlugin(options => {
  options.Whatever = 42;
});

services.AddFusionCache()
  .WithAllRegisteredPlugins()
;

It goes without saying, but you can register multiple plugins, all responding to the same IFusionCachePlugin service, and they will all be picked up by FusionCache when needed:

services.AddTransient<IFusionCachePlugin, MyFirstPlugin>();
services.AddTransient<IFusionCachePlugin, MySecondPlugin>();

services.AddFusionCache()
  .WithAllRegisteredPlugins()
;

How to use a plugin without DI

Just create an instance of your plugin and pass it to the cache.AddPlugin method.

var firstPlugin = new MyFirstPlugin();
var secondPlugin = new MySecondPlugin();

var cache = new FusionCache(new FusionCacheOptions());

cache.AddPlugin(firstPlugin);
cache.AddPlugin(secondPlugin);

Remember that, in case the Start method of your plugin throws and exception, an InvalidOperationException would also be thrown by the AddPlugin method itself (with the original exception as the inner one).

Instead, in the DI way, this is already taken care of and no unhandled exception will be thrown.

In both cases the original exception will be logged.

How to remove a plugin

Normally there's no need to remove a plugin manually: if you just want to clean things up "at the end" (and you should do it) you don't have to do anything because when a FusionCache instance is disposed, all added plugins will be automatically stopped and removed.

But if, for whatever reason, you need to keep using a FusionCache instance after removing a particular plugin you've previously added, you can call the cache.RemovePlugin method: it will automatically call the Stop method of the plugin and then remove it.

👩‍💻 A practical example

Want to follow a complete, end-to-end example to create your first plugin? There's one available 🧩 right here.