I have a WCF application, running on .NET 3.5 SP1, hosted in IIS7, on a Windows Server 2008 64-bit.
In our architecture, there is 1 instance of the application per client, DLLs are copied in a separate directory for each client. In IIS, we host 5 or so clients per application pool, each client having its own application/virtual directory/physical directory configured.
This config works fine for our current version, which uses .NET 2.0 ASMX Webservices with WSE.
When we put our new version using WCF in test, it worked fine when the application pool has only one application in it. When we put 2 applications in the same pool, the services starts returning null for no reason while it is not when isolated.
Our application pool managed pipe line is “Classic”, and I have also tried in “Integrated” mode, the problem is still there.
Anyone have some ideas of what is going on ?
The case with Microsoft has been resolved.
This is a bug in .Net frameowkr 2.0 and a hotfix will be available shortly.
The KB is 971030.
The problem was related on how the CLR loads assemblies into a app domain.