Web site with multiple languages can’t use VB.NET classes in C# code

I’m developing a new functionality for web site project with VB.NET default language in VS 2008. As my preferred language is C# I create subfolder for C# code in the App_Code folder and add appropriate codeSubDirectories element to web.config file. The problem is that I can’t refer VB.NET classes in my C# code. All VB.NET classes and structures are placed in global namespace in the App_Code. But even if I place some VB.NET class in the same namespace I’ve use for my classes in C#, I still can’t use them. Also, I’ve try to move my class to global namespace but this also doesn’t help me.

ASP.NET What causes: It is an error to use a section registered as allowDefinition=’MachineToApplication’ beyond application…?

I have an ASP.NET web site. I keep getting the error below in VS 2008. The site works fine from a browser. I have made every folder using IIS manager an ASP.NET app. Why does it keep complaining? The site’s folder is below a parent folder.
I am not familiar with web site apps instead of web application app. Where are the options to use IIS or the internal web server like WAP has?