Install the package(s)

Shale is provided as two packages to minimise the dependencies needed for your app’s plugin authors: Shale and Shale.Abstractions. Like the Microsoft.Extensions.* packages, the .Abstractions package contains only the required interfaces (IPlugin in this case) and references to the dependent interfaces (like IServiceCollection and IConfiguration).

In general, your host application will need to reference Shale (to actually load the plugins) and whatever assembly your plugins will reference will need to reference Shale.Abstractions.

Load Shale during startup

Assuming your .NET app uses the Microsoft.Extensions.DependencyInjection APIs, you likely already have an IServicesCollection object in your startup, but if you don’t already, you’ll need to create one.

Wherever you’re setting up your DI container, just add a call to Shale’s LoadPlugins extension method:

  var services = new Microsoft.Extensions.DependencyInjection.ServiceCollection();
services.AddPlugins(); // <-- This is where Shale comes in
// trimmed for brevity

Configure Shale

Shale’s fluent API should make it pretty easy to configure things during registration:

  var modulesPath = Path.Join(Environment.CurrentDirectory, "Modules");
services.AddPlugins<IAppPlugin>(c => {
	return c.AlwaysLoad<IGreeter>()
		.AddSearchPath(modulesPath)
		.ShareTypes(typeof(ISharedType))
		.OnlyLoadIf(p => p.Enabled == true)
		.UseConsoleLogging()
		.UseDefaultRegistration(RegistrationType.Transient);
});

Load your plugins

Once you have your plugins, put the build output in any of your configured search paths, one directory per plugin, with the directory named the same as the plugin assembly file.

For example, by default Shale will search the “./Plugins” directory relative to both the current directory and the executable directory, so you could place plugins as below:

  │   HostApp.exe
└───Plugins
	└───Plugin1
	│	│   // trimmed for brevity
	│	│   HostApp.Common.dll
	│	│   Plugin1.dll
	│	└───Plugin1.deps.json
    └───Plugin2
		│   // trimmed for brevity
		│   HostApp.Common.dll
		│   Plugin2.dll
		└───Plugin2.deps.json