Question: Is there a mechanism in the .NET Framework to hide one custom Type from another without using separate projects/assemblies? I'm using C# with ASP.NET in a Website project. Note: I'm not talking about access modifiers to hide members of a Type from another type - I mean to hide the Type itself.

Background: I'm working in an ASP.NET Website project and the team has decided not to use separate project assemblies for different software layers. Therefore I'm looking for a way to have, for example, a DataAccess/ folder of which I disallow its classes to access other Types in the same ASP.NET Website project. In other words I want to fake the layers and have some kind of security mechanism around each layer to prevent it from accessing another.

Obviously there's not a way to enforce this restriction using language-specific OO keywords so I am looking for something else, for example: maybe a permission framework or code access mechanism, maybe something that uses meta data like Attributes. Even something that restricts one namespace from accessing another. I'm unsure the final form it might take.

If this were C++ I'd likely be using friend to make as solution, which doesn't translate to C# internal in this case although they're often compared.

I don't really care whether the solution actually hides Types from each other or just makes them inaccessible; however I don't want to lock down one Type from all others, another reason access modifiers are not a solution. A runtime or design time answer will suffice. Looking for something easy to implement otherwise it's not worth the effort ...