Injecting conditions into FluentValidation rule

Question

Is it possible to inject a condition (like a regex string, or integer) into a FluentValidation validator? That is, say I have multiple clients where each has different password requirements; can I inject that into the validator?

Something like:

public RegistrationValidator(int minLength, string regex)
{
    RuleFor(registration => registration.Login).MinimumLength(minLength);
    RuleFor(registration => registration.Password).Matches(regex);
}

If so, how exactly is it done? The closest I can figure is with root context data, but I feel like this should be simpler than that.

Answer 1

Yes, it's possible. you can inject any services you want from the constructor method in the validation class and create your custom validator. to define a rule like that you have 3 options.

1 - When / WhenAsync

2 - Must / MustAsync

3 - Custom / CustomAsync

For example, I want to inject my DbContext in the validator class, load the user and create a suitable validation for the current user.

User Class :

public class User
{
    public int Id { get; set; }
    public string PhoneNumber { get; set; }
    public string PhoneNumberRegax { get; set; }
}

DTO class :

public class UserDto
{
    public int Id { get; set; }
    public string PhoneNumber { get; set; }
}

Validator Class

public class UserDtoValidator : AbstractValidator<UserDto>
{
    private readonly UserDbContext _context;
    public UserDtoValidator(UserDbContext context)
    {
        _context = context;
        RuleFor(x => x).Must(CheckPhoneNumberRegax);
    }

    private bool CheckPhoneNumberRegax(UserDto inputUser)
    {
        var user = _context.Users.Single(o => o.Id = inputUser.Id);
    
        var r = new Regex(user.PhoneNumberRegax, RegexOptions.IgnoreCase);
        return r.IsMatch(inputUser.PhoneNumber);
    }
}

Note: if use FluentValiation as ASP.NET Core Default validator must not use Async methods in the validator because ASP.NET Core validation pipeline is synchronous.