c# Assembly.LoadFrom with dynamic AssemblyResolve

Question

I'm kind of stuck with dynamically loading plugins:

Theory: (Plugin) Dlls in a specific folder:

foreach(string path in Directory.GetFiles(...))
{
    Assembly myPlugin = Assembly.LoadFrom(path);
    foreach(Type type in myPlugin.GetTypes().Where(t => typeof(myPluginBaseClass).isAssignableFrom(t)))
    {
        Activator.CreateInstance(type);
    }
}

So far so good. Now there are issues with additional references in those assemblies, which can be solved by catch(ReflectionTypeLoadException) (to removed all null Types) and AppDomain.CurrentDomain.AssemblyResolve += ... (to manually look for those missing dlls)

Now here is the issue: The referenced missing assemblies are specific for each implemented Plugin, so I need a individual search behavior implemented in each Plugin. My ideas / solutions so far:

• Having a global list of all possible DLL directories in my main application -> stupid because this won't allow to add further plugins without changing the main application code
• Having a (non static) dictionary of specific dll paths in each plugin -> can be forced by the myPluginBaseClass using virtual/abstract; But can't be accessed before creation of the instance (where those AssemblyResolveEvents are fired), so not helpful
• Having a (static) dictionary of specific dll paths in each plugin -> can be read before instantiation by using Reflection, but I can't add this to my myPluginBaseClass as a defined template, so errors possible
• Creating a individual Domain for each plugin and let them handle their own AssemblyResolveEvent -> But how?

I hope you can help!

Thanks in advance! Robin

Answer 1

Create domain seems to be adequat solution for plugin pattern.

You don't really need to define AssemblyResolve, you can simply configure the directory where AppDomain can find dependencies.

https://msdn.microsoft.com/fr-fr/library/system.appdomainsetup.applicationbase(v=vs.110).aspx