How to use the same singleton instance from main appdomain in childs appdomain

Question

I have a reference to a singleton (CacheLayer ) from a class (InnerModuleInfoLoader) loaded inside a child domain. The problem is that this reference is not the same instance as for the rest of the code living in main domain. I wonder if exists any way to circumvent the execution isolation of appDomain to use the instance of the singleton?

Here is the code:

AppDomain subdomain = this.CreatedChildDomain(AppDomain.CurrentDomain);

Instantiating class from subdomain

var loader = (InnerModuleInfoLoader) subdomain.
    CreateInstanceFrom(loaderType.Assembly.Location, loaderType.FullName).Unwrap();

Inside InnerModuleInfoLoader: Bellow I would like that CacheLayer.Instance will be the same for parent and subdomains.

var server = CacheLayer.Instance.Get<string>("Server");

Singleton

public sealed class CacheLayer
{
    private static readonly CacheLayer instance = new CacheLayer();
    private static readonly ObjectCache cache;
    static CacheLayer()
    {
        cache = MemoryCache.Default;
    }
    private CacheLayer(){}
    //More code omitted
}

Subdomain creation

protected virtual AppDomain CreatedChildDomain(AppDomain parentDomain)
{
    Evidence evidence = new Evidence(parentDomain.Evidence);
    AppDomainSetup setup = parentDomain.SetupInformation;
    return AppDomain.CreateDomain("ModuleFinder", evidence, setup);
}   

Answer 1

I wonder if exists any way to circumvent the execution isolation of appDomain to use the instance of the singleton?

You can use MarshalByRefObject, that is, make your CacheLayer class inherit from it.

Keep in mind, marshaling calls between AppDomains comes at a performance penalty. I would consider just having two difference caches for each AppDomain.