Summary

In this chapter, we've looked in some detail at certain aspects of security in .NET, focusing in particular on the operation of code access security (CAS). We have examined the default policy that ships with .NET, and used this to understand the relationship between permissions, permission sets, and code groups, and have gone on to examine how the permissions are implemented using classes that implement the IPermission interface. This discussion threw up the fact that relatively little of the .NET security architecture is actually implemented within the CLR - instead much of this infrastructure is implemented by classes in the System.Security and related namespaces. This has the advantage that it makes for a highly extensible architecture, in which you can for example define and plug in your own custom permissions. We presented a couple of samples that illustrated this technique.