Data validation is extemely important. The problem is that it can create a lot of excess code. Plus you end up in the position of having similar validation code throughout your application, violating the DRY principle. In this video, I am going to introduce you to Fluent Validation, a free tool to help make your validation clean, easy to create, and easy to maintain. As a bonus, it even works on models that you don't own and cannot change.