Validating data

FluentValidation allows you to define strongly typed validation rules in a human-readable way.

You create a validator for a type by inheriting from AbstractValidator<T>, where T is the type that you want to validate. In the constructor, you call the RuleFor method to define one or more rules. If a rule should run only in specified scenarios, then you call the When method.

Understanding the built-in validators

FluentValidation ships with lots of useful built-in validator extension methods for defining rules, as shown in the following partial list, some of which you will explore in the coding task in this section:

• Null, NotNull, Empty, NotEmpty
• Equal, NotEqual
• Length, MaxLength, MinLength
• LessThan, LessThanOrEqualTo, GreaterThan, GreaterThanOrEqualTo
• InclusiveBetween, ExclusiveBetween
• ScalePrecision
• Must (aka predicate)
• Matches (aka regular expression), EmailAddress, CreditCard
• IsInEnum, IsEnumName...