Minor bug in WF 3.0 RC1 designer

As stated in my previous post, the WF designer in version beta 2.2 was poor. It was very slow and came up with some non-sense error every 10 minutes or so. The changes in version 3.0 RC are obvious: the designer is still a bit slow but very stable. You can hardly fault it. However, I've noticed a small bug: if you define an event arguments class derived from ExternalDataEventArgs and use it to wire up an event to a handleExternalEventActivity even though it does compile and work just fine the designer shows it as an error (as shown in the image).

Let's take an example. We define an event arguments class inherited from ExternalDataEventArgs such as:

[Serializable]
public class MyExternalDataEventArgs : ExternalDataEventArgs
{
public MyExternalDataEventArgs(Guid instanceID) : base(instanceID)
{
}
}

Then we define the data exchange interface:

[ExternalDataExchange]
public interface IExternalEvents
{
event EventHandler MyEvent;
}

and then we create a workflow, drag a handle external event activity on the flow and wire it to our IExternalEvents interface and MyEvent event - which translates to:

this.handleExternalEventActivity1.EventName = "MyEvent";
this.handleExternalEventActivity1.InterfaceType = typeof(DerivedWorkflowClass.IExternalEvents);
this.handleExternalEventActivity1.Name = "handleExternalEventActivity1";

Now we can see the error icon, but still we can build the project with no problem, not even a warning.

That being said, sometimes as you come in and out of the designer the error icon disappears and the re-appears, but I couldn't see any patter in this behavior and most of the times the error icon is on.

This issue comes up on RC1 of .NET Framework 3.0 Runtime Components using:
Extensions for Windows WF
Windows Workflow Foundation Tools for Visual Studio

Orcas Technology Preview - .NET Framework 3.0 Development Tools 1.0
Microsoft Visual Studio Code Name Orcas Community Technology Preview - Development Tools for WinFX

I will report the bug on http://connect.microsoft.com/wf tomorrow. However, my point here is that after a month of pretty intense development on WF 3 RC1 this is the only bug I've found and as you can see it is a minor inconvenient so I guess it backs up the previous post proving that it is a stable release.