This security measure deals with setting permissions on projects, files, code and resources from anything unauthenticated. The CodeAccessPermission class comes in to play in allowing administrators the power to delegate certain types of access to various resources, thus ensuring authorized access only. It works alongside the trust element key within the web.config file in setting code access security (Full is the default):

<trust level="Full | High | Medium | Low | Minimal" originUrl="url"/>

Read Secure Coding Guidelines for the .NET Framework and Secure Coding Guidelines for more info .

Furthermore, as this also applies to all aspects in this article, if you really, really need the utmost security for very critical data, you do have a couple of nice options:

1. Retrieve sensitive information and settings using serialization , that converts data to bytes for any type of transmission, that later gets deserialized on the other end.
   
2. Directly reference an object's (dll/assembly) metadata (binary info about your dll) and other information or invoke methods contained within it during run time via Reflection using the System.Reflection namespace

Look at ASP.NET Security for more info and if you got the time read Microsoft's 608 page - Building Secure ASP .NET Applications treatise. Furthermore, peruse ASP.NET Architecture as well.

Now that we've dealt with security as an good overview, we now can move on to the actual components involved in making our application's architecture robust and high-performance. We'll first begin looking at some best practices that will determine general application health, before we discuss the best methods with each Tier.