FluentValidation-Library 1-configue with .net core 3.1 2-use server side Validation 3-client side validation NotNull/NotEmpty Matches (regex) InclusiveBetween (range) CreditCard Email EqualTo (cross-property equality comparison) MaxLength MinLength Length 4- Specifying a RuleSet for client-side messages 5-Injecting Child Validators "Not Compelted"