"With PostSharp, you can develop custom attributes that change your code. And you can do more!

PostSharp is a post-compiler: an open platform for analysis and transformations of .NET assemblies after compilation.

Aspect-Oriented Programming (AOP) or Policy Injection are two of the major applications, but only two of them.

PostSharp Laos is a high-level aspect weaver that makes aspect-oriented programming (AOP) extremely easy. But Laos is only an illustration of the complete Platform. PostSharp is used to perform low-level MSIL injection. It serves as a base for persistence layers, optimizers or custom AOP weavers."

PostSharp link