Loading Assemblies into another AppDomain and Type Inspection

If you load the assembly into another appdomain then you should of course create instances there and use them there. Other than that, not sure what problem you have run into.

Updates

1. added code to pick type from list
2. changed to only pass type names across the domains as strings

using System;
using System.IO;
using System.Reflection;
using System.Runtime.Remoting;

public class MainClass : MarshalByRefObject
{
    static void Main(string[] args)
    {
        if (args.Length == 0)
        {
            Console.WriteLine("usage: {0} assembly", Path.GetFileName(Assembly.GetExecutingAssembly().Location));
            return;
        }
        AppDomain other = AppDomain.CreateDomain("other");
        Type myType = typeof(MainClass);
        // create a loader instance in the new domain
        MainClass loader = (MainClass)other.CreateInstanceAndUnwrap(myType.Assembly.FullName, myType.FullName);
        string assemblyName;
        string[] types = loader.LoadAssembly(args[0], out assemblyName);
        Console.WriteLine("Loaded assembly {0}.", assemblyName);
        Console.WriteLine("Types:");
        for(int i = 0; i < types.Length; i += 1)
        {
            Console.WriteLine("[{0}] {1}", i, types[i]);
        }
        Console.Write("Enter index of type to create, -1 to exit: ");
        int create = Int32.Parse(Console.ReadLine());
        if (create < 0)
        {
            return;
        }
        Console.WriteLine("Creating instance of type {0}", types[create]);
        Console.WriteLine("Type of the created instance was: {0}", loader.CreateInstance(assemblyName, types[create]));
    }

    string[] LoadAssembly(string path, out string assemblyName)
    {
        Console.WriteLine("LoadAssembly executing in appdomain {0}", AppDomain.CurrentDomain.FriendlyName);
        Assembly assembly = Assembly.Load(File.ReadAllBytes(path));
        assemblyName = assembly.FullName;
        return Array.ConvertAll<Type, string>(assembly.GetExportedTypes(), x => x.FullName);
    }

    string CreateInstance(string assemblyName, string typeName)
    {
        Console.WriteLine("CreateInstance executing in appdomain {0}", AppDomain.CurrentDomain.FriendlyName);
        object instance = Activator.CreateInstance(assemblyName, typeName).Unwrap();
        // do something useful with the instance here
        return instance.GetType().FullName;
    }

    public override object InitializeLifetimeService()
    {
        return null;
    }
}

Sample output for log4net.dll:

$ mono main.exe log4net.dll
LoadAssembly executing in appdomain other
Loaded assembly log4net, Version=1.2.10.0, Culture=neutral, PublicKeyToken=a5715cc6d5c3540b.
Types:
[0] log4net.Core.SecurityContext
[1] log4net.Core.LoggerWrapperImpl
[2] log4net.Core.LogImpl
[3] log4net.Core.DefaultRepositorySelector
...
[160] log4net.Appender.AspNetTraceAppender
[161] log4net.Appender.FileAppender
...
[197] log4net.Repository.LoggerRepositoryConfigurationResetEventHandler
[198] log4net.Repository.LoggerRepositoryConfigurationChangedEventHandler
Enter index of type to create, -1 to exit: 161
Creating instance of type log4net.Appender.FileAppender
CreateInstance executing in appdomain other
Type of the created instance was: log4net.Appender.FileAppender