CODEWITHSUNDEEP
c#reflection
Devator
Devator

Reputation: 3904

C# get unreferenced assemblies

The problem

I'm working on a project with a plugin like system. The project structure is defined as follows:

- Solution
    - Project A (Cli)
    - Project B (Core logic)
    - Project C (Plugin)

Project A is the startup project, Project B contains the core logic and Project C is a plugin, which implements an interface in project B. Project A only has a reference to Project B and Project C only has a reference to Project B.

To visualize:
visualization

Since I do not reference Project C from Project B (and do not instantiate the class directly), code like AppDomain.CurrentDomain.GetAssemblies() (inside Project B) does not return Project C.

However, once I do (from Project B): var MyImplementation = new MyImplementation(), AppDomain.CurrentDomain.GetAssemblies() does return the assembly, since it's known and loaded at runtime as I instantiated the class MyImplementation explicitly from code.

The question

From Project B, I want to get all assemblies which implement a specific interface from Project B and instantiate them.

So, how do I get these (seemingly) unknown assemblies to get loaded at runtime?

Upvotes: 0

Views: 330

Answers (1)

Coding Seb
Coding Seb

Reputation: 93

I don't think it's possible to know if an assembly contains a class that implement your interface without loading it.

What you can do is provide a directory where you put all your plugins assemblies.

So you can load your plugins in your AppDomain like this : 

public static Assembly[] MyPlugins { get; private set; }

public static void LoadAssemblies()
{
   MyPlugins = Directory.GetFiles(lookingDirectory, "*.dll")
                .Select(assemblyPath =>
                {
                    AssemblyName an = AssemblyName.GetAssemblyName(assemblyPath);
                    return Assembly.Load(an);
                })
                .ToArray();
}

And then you can find all types that implements your interface like this :

MyPlugins.SelectMany(assembly => assembly.GetTypes())
    .Where(type => typeof(IYourInterface).IsAssignableFrom(type))
    .Select(type => (IYourInterface)Activator.CreateInstance(type))

And then you can iterate on each implementation of your interface to call a shared method for example.

Upvotes: 1

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