The thread tried to read from or write to a virtual address for which it does not have the appropriate access

Question

I have developed a .NET 2.0 extension that acts as a plug in to a 3rd party application. Everything runs fine when run on anything but Citrix. When run over Citrix as a published application the extension crashes randomly which also crashes the 3rd party application.

I have opened up a dump file and have found an exception message that gets reported:

The thread tried to read from or write to a virtual address for which it does not have the appropriate access.

The application does use threading which I suspect where the above occurs, but where exactly is a mystery. If I run the extension locally on the Citrix server (i.e. not as a published app) then it works fine.

Answer 1

The nature of the error message makes it unlikely to be a problem with the .NET 2.0 code. That is because .NET does not allow you to even attempt to read/write memory that it is not suppose to.

• Check to see if you have any unsafe code in your extension. Code of this nature may be able to skirt the verification checks the CLR would normally perform.
• Check to see if the code your extension uses any unmanaged code (COM or P/Invoke). The error may be generated there.
• It is possible that there is a bug in the .NET CLR that causes problems when run in Citrix environment.

The first thing I would do is analyze that dump file to see which module the fault occurred in. You can download the Windows Debugging Tools to assist with this effort.

Answer 2

I got the identical message when opening a project using Schneider Unity Pro. After a tedious and lengthy process of elimination, the problem was isolated to the “Do not keep history of recently opened documents” policy being enabled.