Catel is a powerfull MVVM toolkit that provides a flexible approach to use external validation frameworks.
Could you provide an implementation of a provider for a build-in FluentValidation integration with Catel?
I'm really have a partial implementation where I had to write custom attributes to full map the Catel validation concepts (field errors, field warnings, business rules errors, and business rules warnings) to the FluentValidation ones.
If you are interested in the integration I can provide you the the source code of my approach to solve this problem.