How to create a Plug-in architecture

Problem

You want to create an application which could dynamically load ‘plug-ins’ at runtime.  You want to do this because:

1. you want other people to create plug-ins for your application without exposing your source code
2. you have a module which keeps changing but don't want to recompile your application every time it changes

Solution overview

1. Create an interface which all plug-ins must implement, and have it shared as an assembly referenced by both your application and the plug-ins.
2. Create a plug-in by implementing the interface, and build it as an assembly
3. Let the application know about the plug-in assembly, by using either the app.config file or any similar mechanism.
4. At run time, use Reflection (Activator.CreateInstance method) to create an object of the plug-in and store in a variable of the interface type.

Suggested references

• http://www.msdn.microsoft.com/vstudio/default.aspx?pull=/library/en-us/dnaspp/html/pluginframework.asp
• http://www.codeproject.com/csharp/Plugins.asp