AppDomain Sandboxing issues using PermissionSet

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C#

C#4.0

AppDomain

I'm trying to create a sandboxed appdomain. It isn't to difficult so far. I just came across one problem I couldn't seem to fix:

This is a shortened version of my classes, but you should get the idea:

public class LocalLoader : CrossAppDomainObject
{
    public LocalLoader()
    {
        RemoteLoader remoteloader;
        
        AppDomainSetup setup = new AppDomainSetup();
        setup.ApplicationName = "MyAppDomain";
        setup.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory;
        //..some path settings, not relevant
        
        PermissionSet permissions = new PermissionSet(PermissionState.None);
        permissions.AddPermission(new SecurityPermission(SecurityPermissionFlag.Execution));
        
        appdomain = AppDomain.CreateDomain("MyAppDomain", AppDomain.CurrentDomain.Evidence, setup, permissions, null);
        
        //Create an instance of RemoteLoader in a new appdomain!
        remoteloader = (RemoteLoader)appdomain.CreateInstanceAndUnwrap(Assembly.GetExecutingAssembly().FullName, typeof(RemoteLoader).FullName);
    }
}

public class RemoteLoader: CrossAppDomainObject
{
}

The CrossAppDomainObject is simply put a class which inherits MarshalByRefObject and overrides the InitializeLifetimeService() method. Like this (also shortened):

public abstract class CrossAppDomainObject : MarshalByRefObject
{
    public sealed override object InitializeLifetimeService()
    {
        return null;
    }
}

It will cause the lifetime of the connection to be infinite, a must have in my project.


When I do the appdomain.CreateInstanceAndUnwrap I receive this error:

Inheritance security rules violated while overriding member: 'MyApplication.CrossAppDomainObject.InitializeLifetimeService()'. Security accessibility of the overriding method must match the security accessibility of the method being overriden.

I've looked around for settings I should allow in my PermissionSet but I couldn't find anything that worked. Or should I add additional things to my CrossAppDomainObject?

Anyone an idea how I should fix this?
Answers are much appreciated.