DotNetCorePlugins/samples/aspnetcore

ASP.NET Core Sample

This sample contains 4 projects which demonstrate a simple plugin scenario.

1. 'Abstractions' defines common interfaces shared by the web application (host) and plugins
2. 'MainWebApp' is an ASP.NET Core application which scans for a 'plugins' folder in its base directory and attempts to load any plugins it finds
3. 'WebAppPlugin1' references 'Abstractions' and implements IWebPlugin. This plugin has a dependency on AutoMapper version 6.
4. 'WebAppPlugin2' is the same as plugin1, but it uses AutoMapper version 7.

Normally, in .NET Core applications you cannot reference two different versions of the same assembly. However, as this sample demonstrates, using .NET Core plugins you can load and use two different versions.

• http://localhost:5000/plugin/v1 responds with

This plugin uses AutoMapper, Version=6.2.2.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005

• http://localhost:5000/plugin/v2 responds with

This plugin uses AutoMapper, Version=7.0.1.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005

There are some important types, however, which must share the same identity between the plugins and the host. To ensure type exchange works between the host and the plugins, the MainWebApp project uses the sharedTypes parameter on PluginLoader.CreateFromAssemblyFile.

    var loader = PluginLoader.CreateFromAssemblyFile(
        pluginAssembly,
        sharedTypes: new[]
        {
            typeof(IApplicationBuilder),
            typeof(IWebPlugin),
            typeof(IServiceCollection),
        });

This is important because the plugins in this sample are compiled for ASP.NET Core 2.0 interfaces, but the MainWebApp uses ASP.NET Core 2.1. If not for this parameter, the plugins would also attempt to use a private copy of the ASP.NET Core implementations and type exchange between the plugin and the web app would fail to resolve IApplicationBuilder and IServiceCollection as the same type.