What are some examples of Fluent Validation in C#?

What are some examples of Fluent Validation in C#?

Fluent Validation is a popular library for building strongly-typed validation rules in C#. Here are a few examples:

1. Basic Validation:

   public class UserValidator : AbstractValidator<User>
   {
       public UserValidator()
       {
           RuleFor(user => user.Name).NotEmpty().WithMessage("Name is required.");
           RuleFor(user => user.Age).InclusiveBetween(18, 60).WithMessage("Age must be between 18 and 60.");
       }
   }
   

2. Custom Validation:

   RuleFor(user => user.Email)
       .Must(BeAValidEmail).WithMessage("Invalid email format.");
   

3. Complex Validation:

   RuleFor(user => user.Password)
       .MinimumLength(8)
       .Matches("[A-Z]").WithMessage("Password must contain at least one uppercase letter.");
   

Would you like to see more examples or details on a specific validation rule?

Can you explain the custom validation example?

Sure! In the custom validation example, we use the Must method to define a custom rule. The BeAValidEmail method is a custom function that checks if the email format is valid. Here's how you might implement it:

private bool BeAValidEmail(string email)
{
    return Regex.IsMatch(email, "^[^\s@]+@[^\s@]+\.[^\s@]+$");
}

This method uses a regular expression to validate the email format. If the email doesn't match the pattern, the validation fails, and the specified error message is shown.

What if I want to validate a list of items?

You can validate a list of items by using the ForEach method. Here's an example:

RuleForEach(user => user.Roles).NotEmpty().WithMessage("Each role must be specified.");

This will ensure that every item in the Roles list is not empty. You can also apply other rules similarly.

Thanks! This is really helpful.

You're welcome! I'm glad you found it helpful. If you have any more questions about Fluent Validation or anything else, feel free to ask!