You might often want to validate parameters in your methods to ensure they have valid data. Most importantly, you might often want to protect your publicly exposed API methods by ensuring that the parameters in those methods have valid values. This would ensure that your APIs work consistently. The solution to this problem is by implementing aspect-oriented programming, or AOP.
Aspect-oriented programming separates the concerns of your application, reduces code duplication and clutter, and improves the maintainability and readability of your code. There are several tools out there that you can use to implement AOP in your applications. PostSharp is one of the most widely used AOP frameworks.