PostSharp is a great open-source tool that allows you to encapsulate the non-business logic in custom attributes. That’s the Aspect Oriented Programming paradigm main goal: the separation of concerns.
This tool heps you to free the business logic from the infrastructure code such as:

Transactions
Logging
Permissions / Security
Exceptions handling
Caching
Settings

Your code will be cleaner than never.
…and why do I [...]

In this post I will describe the basics of MAF to quickly introduce this framework.
The Managed Add-In Framework is an Add-In architecture built on top of the .Net Framework aimed to address the following problems:

Loading/Unloading
Sandboxing (Add-ins can be sandboxed to a particular security permission set)
Isolation (isolation boundary between the Host and the Add-ins)
Lifetime Management
Discovery
Activation
Backwards compatibility
Forwards [...]