C# - Returning Value From a Method in Another AppDomain

Question

I have a scenario in which I am adding DLLs to the GAC from actions in my C# code. I then need to do an Assembly.Load on the newly added DLL. However, since the DLL wasn't in the GAC when the process started, it returns null.

So, I see that code can be run in a different AppDomain, which would result in the DLL being available from the GAC in the separate AppDomain.

How can I return the value from the other AppDomain to my main thread?

I simply want to run:

var type = Assembly.Load(assembly).GetType(className);

And have it return from the other AppDomain to my main thread.

Answer 1

You'll have to play a little with .NET Remoting. Your objects loaded on the other AppDomain will need to derive from the MarshalByRefObject class (http://msdn.microsoft.com/en-us/library/system.marshalbyrefobject.aspx).

Just to save time, here's the code from that link:

using System;
using System.Reflection;

public class Worker : MarshalByRefObject
{
    public void PrintDomain() 
    { 
        Console.WriteLine("Object is executing in AppDomain \"{0}\"",
            AppDomain.CurrentDomain.FriendlyName); 
    }
}

class Example
{
    public static void Main()
    {
        // Create an ordinary instance in the current AppDomain
        Worker localWorker = new Worker();
        localWorker.PrintDomain();

        // Create a new application domain, create an instance 
        // of Worker in the application domain, and execute code 
        // there.
        AppDomain ad = AppDomain.CreateDomain("New domain");
        Worker remoteWorker = (Worker) ad.CreateInstanceAndUnwrap(
            Assembly.GetExecutingAssembly().FullName,
            "Worker");
        remoteWorker.PrintDomain();
    }
}

/* This code produces output similar to the following:

Object is executing in AppDomain "source.exe"
Object is executing in AppDomain "New domain"
 */