Click here to Skip to main content
Click here to Skip to main content

How to create an easy plugin-system in C#

, 15 Feb 2013
Rate this:
Please Sign up or sign in to vote.
How to build an easy plugin system with C# which only takes about 30 lines of code!

Introduction

This article will describe how to implement a simple Plugin-system into your C#-Application which can be very useful for several situations your tool has to implement different behavior. This code snippet will only make use of standard .NET classes which are built-in the Microsoft Framework! No 3rd party tools are needed!

Background

Since I started developing C#-Desktop-Applications about 4 years ago I really ran across several problems. One was, to implement a stable plug-in system with which you could easily spread code and functionality. One big problem was, that no one nowhere had a good tutorial on how to build this. So I decided to write my own, first tutorial in English. So please be gentle with my grammar.

Using the code

The .NET Framework offers two possibilities to load assemblies to the current AppDomain. The following code uses the same functionality Visual Studio has when you're adding a new reference to your project. The code to include an assembly uses the System.Reflection namespace and looks as following:

//This code loads a new dll to the current AppDomain.
Assembly.LoadFrom(@"YourPathToTheDLL");

Now, the assembly is loaded into your application but you can't really use anything in it because normally you don't really know what functionality the plug-in offers. Also, it's pretty easy to access a DLL in a normal executable but the way back can be very annoying.

Now, to access the DLL, we need its assembly name which should be equal to the main-namespace of it. Unfortunately, there is no way to get the default namespace of a dynamically added assembly in C#. One possibility is now to always expect the plug-in to have the same namespace as the application we're loading it in. But that doesn't matter at the moment. Once we've loaded our plug-in, we start using it via Reflection, which goes as follows.

//Loop through all opened assemblies in the current AppDomain
foreach (Assembly a in AppDomain.CurrentDomain.GetAssemblies())
{
    foreach (Type t in a.GetTypes())
    {
        if (t.GetInterface("MyFunctionInterface") != null)
        {
            try
            {
                MyFunctionInterface pluginclass = Activator.CreateInstance(t) as MyFunctionInterface;
                pluginclass.doSomething();
                return;
            }
            catch
            {
            }
        }
    }
}

Easy, right? Working with plug-ins is actually no problem if you understand how easy you can write dynamic code.

Points of Interest

There is also a possibility in the System.Reflection to load only the bytes of a DLL. By now, I haven't really had a chance of using it because I can't really imagine a scenario where this would be more useful than linking to the location of the file.

History

  • Version 1.0.0.0: Initial with all the information and a working .NET Solution to show how plug-ins can work!

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Dread_Sharp
Software Developer (Junior)
Switzerland Switzerland
I started my apprenticeship as a computer scientist in 2009 and now I'm currently working on my degree. I love music and the combination between IT and music. That's why I have a studio where i produce music.

Comments and Discussions

 
QuestionGreat Tip PinmemberJorge Gómez P.28-Mar-14 5:39 
QuestionOptimization Pinmemberklinkenbecker5-Jan-14 12:28 
QuestionNice Pinmemberklinkenbecker5-Jan-14 9:28 
QuestionDoesnt Work. PinmemberYukiiii15-Nov-13 18:06 
AnswerRe: Doesnt Work. PinmemberDread_Sharp21-Nov-13 5:13 
AnswerRe: Doesnt Work. Pinmemberklinkenbecker5-Jan-14 9:27 
Questionan improvement Pinmemberleizhiyuan16-Feb-13 18:32 
AnswerRe: an improvement PinmemberDread_Sharp21-Feb-13 20:09 
GeneralRe: an improvement Pinmemberleizhiyuan21-Feb-13 20:10 
GeneralMy vote of 5 Pinmemberrevive13915-Feb-13 4:20 
GeneralMEF! Pinmemberdb7uk15-Feb-13 3:23 
GeneralRe: MEF! PinmemberDread_Sharp15-Feb-13 3:29 
GeneralRe: MEF! Pinmemberdb7uk15-Feb-13 3:34 
QuestionIdea to extend and some optimizations PinmemberReinhard Ostermeier15-Feb-13 2:51 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Mobile
Web02 | 2.8.140709.1 | Last Updated 15 Feb 2013
Article Copyright 2013 by Dread_Sharp
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid