VerificationException in the property grid, triggered from OnPropertyChanged

We have recently upgraded to version 7.0.454.23404 of the elements package - largely because we wanted to migrate to .NET 4

However, now we have an incredible amount of instability. Basically, when we are showing an object in a property grid that supports multiple selection we get VerificationExceptions when the OnPropertyChanged event is triggered.

The source of the exception is coming from Mindscape.Elements.

In our case, the OnPropertyChanged raises a weak event - see below. In the debugger, I can see the ee.TargetReference is "Mindscape.WpfElements.PropertyEditing.Many

        /// <summary>
        /// Raise event
        /// </summary>
        /// <param name="sender">The sender</param>
        /// <param name="e">The EventArgs to use for event</param>
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1030:UseEventsWhereAppropriate"), System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2109:ReviewVisibleEventHandlers")]
        public void Raise(object sender, EventArgs e)
        {
            bool needsCleanup = false;
            foreach (EventEntry ee in eventEntries.ToArray())
            {
                // It launches the exception here...
                needsCleanup |= ee.Forwarder(ee.TargetReference, sender, e);
            }
            if (needsCleanup)
                RemoveDeadEntries();
        }

Some research has come up with a few things, but I'm not sure if any of them apply. See this for example.

Any ideas?

Just an additional comment.... Some people suggest installing the following patch: patch

I am about to test that now...

But what do we do on Windows 8?

Edit: I am completely unable to install this patch, so I am out of options for this...

Hi Eliz,

I have not been able to reproduce this issue. Could you please send a simple repro project demonstrating a weak property changed event and causing the exception, then I'll look into this further for you and see if we can make a fix.

-Jason Fauchelle

Perhaps this will help. I will still try to put together a test project if I can.

In the following link they are describing the issue fairly well. The main explanation appears to be this:

We recently discovered a compatibility issue in the .NET Framework 4.5. We see that some developers have also seen this same issue. The issue is relatively narrow, however it is possible to hit. We are currently working to resolve this issue, in an update. Let’s look at the issue. There are two pre-requisites that must be true in order to hit this issue with a given type: the type needs to be generic and the CLR verifier needs to have been enabled. Declaring an assembly as SecurityTransparent, as you will see in the example below, will cause the CLR verifier to be enabled. After those two pre-requisites are satisfied, an app that also satisfies just one of a set of conditions will hit the compatibility issue. These conditions are demonstrated in the example below. Apps that do not satisfy either of the two pre-requisites or any of the conditions are not susceptible to this compatibility issue. For example, if we remove the SecurityTransparent attribute in the example below, then the code is no longer affected.

And this is definitely WeakEvent related, most probably because it deals with generics. Because if I change to a regular delegate than I don't have the issue.

I am looking at changing my ViewModelBase class to a more .NET 4.5 way of doing things. If I switch back to a delegate, I can use WeakEventManager to subscribe to the event as a WeakEvent. I'll see if that helps. I'm not sure exactly which 'clients' especially need this to be a WeakEvent, so I am experimenting a bit here.

Hi Eliz,

Just catching up on this, were you able to get this sorted in your application? If not, I'd be happy to still look into it with a repro project.

Regards

-Jason Fauchelle