Is “Code Access Security” of any real world use?

Question

Warning:

Newer versions of .Net and .Net core has have removed and/or changed “Code Access Security” (CAS) since this question was asked.

Original Questio

Answer 1

Although I've never used it, my understanding of CAS was that it could also be used to expand object-oriented design mechanics. For example, say you are developing a massive data access package for a bank that must implement database access and caching. Even though they are part of the same deployment package, given the hypothetical size of the project, the logic should be implemented in separate assemblies since they are sufficiently different problem sets that hinge on different external forces (database infrastructure vs consumer usage).

However, the caching code might need to access some sensitive classes or methods in the data access assembly that consumers of the overall package shouldn't have access to. Therefore these data access classes and methods can't simply be public. Protected methods in the data access assembly with subclasses in the caching assembly could get around some cases, but often times it's an abuse of inheritance. It might simply be more elegant to leave them public with LinkDemands placed on callers for a custom Permission (e.g. DataPackagePermisson) that administrators would only grant to the caching assembly.