Question

I have a application that uses plugins. I load the plugins in another appdomain.
I use the RemoteHandle class from http://www.pocketsilicon.com/post/Things-That-Make-My-Life-Hell-Part-1-App-Domains.aspx to keep object from being garbage collected after 5 minutes.

This works great as long as my application is running, but when it is shutting down i get a InvalidOperationException when Unregistering

internal static void Unregister(MarshalByRefObject value)
    {
        if (value != null && RemotingServices.IsTransparentProxy(value))
        {
            lock (_syncLock)
            {
                ReferencedLease r;
                if (_leaseReferences.TryGetValue(value, out r) && --r.ReferenceCount <= 0)
                {
                    // Note: Dictionary clears key and value from bucket list upon remove.
                    _leaseReferences.Remove(value);
                    r.Lease.Unregister(_instance); // <----- Here i get the exception

                }
            }
        }
    }

Stacktrace:

System.InvalidOperationException: Handle is not initialized.
   at System.WeakReference.set_Target(Object value)
   at System.Runtime.Remoting.IdentityHolder.SetIdentity(Identity idObj, String URI, DuplicateIdentityOption duplicateOption)
   at System.Runtime.Remoting.IdentityHolder.FindOrCreateIdentity(String objURI, String URL, ObjRef objectRef)
   at System.Runtime.Remoting.RemotingServices.InternalUnmarshal(ObjRef objectRef, Object proxy, Boolean fRefine)
   at System.Runtime.Remoting.ObjRef.GetRealObjectHelper()
   at System.Runtime.Remoting.Lifetime.ILease.Unregister(ISponsor obj)
   at Quick3PlugInManager.Sponsor.Unregister(MarshalByRefObject value)
   at Quick3PlugInManager.RemoteHandle`1.Dispose(Boolean disposing)
   at Quick3PlugInManager.RemoteHandle`1.Finalize()

Why do i get that exception?

Answer 1

I would subscribe to the app domains Unload event and see if the application domain has been unloaded already. If so, then I suspect that you don’t need to unregister that handle any longer (just swallow the exception) because the CLR has done it for you. This is just a theory, but it might give you more information.