Workflow Engine: Dynamic plugin loading

In this repository, there is a project integrated with the WorkflowEngine and featuring the implementation of dynamic plugin loading. This code serves as an example of following the tutorial outlined in the documentation.

In this tutorial, we'll implement dynamic plugin loading. This allows you to customize the Workflow Engine by placing compiled DLLs with plugins into the plugins folder. Plugins are classes that implement IWorkflowPlugin, enabling the engine to incorporate new Actions, Rules, etc. Learn more about plugins.

Motivation

You might be interested in this functionality for a variety of reasons:

• You distribute your software with a Workflow Engine to your clients and want to provide them with customization options without needing access to the source code.
• You want to separate dependencies used in the project with the Workflow Engine from those used for plugins.
• You manage a large number of plugins and want to simplify their modification or installation.

Environment Requirements

• Application with integrated Workflow Engine.
• IDE for working with C# code, such as Visual Studio.

Tutorial

In this tutorial, we'll step through implementing dynamic plugin loading, which requires:

1. Writing a PluginLoader class for dynamically loading assemblies.
2. Adding an extension method for loading plugins into the WorkflowRuntime.
3. Creating a new project with plugin implementation and exporting its DLL.
4. Testing and ensuring everything works well.

PluginLoader

This class will inherit from the System class AssemblyLoadContext, aiming to correctly load DLLs and resolve their dependencies at the specified path.

Go to the code >PluginLoader.cs

Extension Method

The extension method allows us to add dynamic loading of plugins into the Workflow Engine Runtime initialization pipeline alongside other settings.

Go to the code >Extensions.cs

Project with Plugin

To test the functionality, we need to create a test project from which we'll import plugins into the Workflow Engine. This requires several steps:

1. Create a new project MyPlugin.

   dotnet new classlib --name MyPlugin
   dotnet sln add MyPlugin
   rm MyPlugin\Class1.cs

2. Add a package reference to WorkflowEngine.NETCore-Core to implement IWorkflowPlugin.

   dotnet add MyPlugin package WorkflowEngine.NETCore-Core

3. Add a new class MyPlugin implementing the IWorkflowPlugin interface. Go to the code >MyPlugin.cs
4. Build the project and copy its DLL to the plugins/{plugin_name}/… folder.

   dotnet build
   mkdir -p DynamicPluginLoading/bin/Debug/net8.0/plugins/MyPlugin
   cp -r MyPlugin/bin/Debug/net8.0/* DynamicPluginLoading/bin/Debug/net8.0/plugins/MyPlugin/

Testing

Finally, we have the ability to connect dynamic plugin loading to the WorkflowRuntime creation pipeline with the plugin name specified.

var runtime = new WorkflowRuntime()
    .WithPlugin(new BasicPlugin())
    // &att>
    .WithDynamicPlugins("MyPlugin")
     // <&att
    .AsSingleServer();

If you've followed the steps exactly, MyPlugin will appear among the plugins in WorkflowRuntime, which you can verify by checking WorkflowRuntime.Plugins.

foreach (var plugin in runtime.Plugins)
{
    Console.WriteLine($"- {plugin.Name}");
}

// Output:
// - BasicPlugin
// - MyPlugin

Conclusion

Now you can easily enhance plugin management in your project.