Validate DateTime with FluentValidator

Question

This is my ViewModel class:

public class CreatePersonModel
{
    public string Name { get; set; }
    public DateTime DateBirth { get; set; }
    public string Email { get; set; }
}

CreatePerson.cshtml

@model ViewModels.CreatePersonModel
@{
    ViewBag.Title = "Create Person";
}

<h2>@ViewBag.Title</h2>

@using (Html.BeginForm())
{
    <fieldset>
        <legend>RegisterModel</legend>

        @Html.EditorForModel()

        <p>
            <input type="submit" value="Create" />
        </p>
    </fieldset>
}

CreatePersonValidator.cs

public class CreatePersonValidator : AbstractValidator<CreatePersonModel>
{
    public CreatePersonValidator()
    {
        RuleFor(p => p.Name)
            .NotEmpty().WithMessage("campo obrigatório")
            .Length(5, 30).WithMessage("mínimo de {0} e máximo de {1} caractéres", 5, 30)
            .Must((p, n) => n.Any(c => c == ' ')).WithMessage("deve conter nome e sobrenome");

        RuleFor(p => p.DateBirth)
            .NotEmpty().WithMessage("campo obrigatório")
            .LessThan(p => DateTime.Now).WithMessage("a data deve estar no passado");

        RuleFor(p => p.Email)
            .NotEmpty().WithMessage("campo obrigatório")
            .EmailAddress().WithMessage("email inválido")
            .OnAnyFailure(p => p.Email = "");
    }
}

When trying to create a person with an invalid date format:

Observations

As in my CreatePersonModel class the DateBirth property is a DateTime type, the asp.net MVC validation has done for me.

But I want to customize the error message using the FluentValidation.

I do not want to change the type of property for various reasons such as:

In a CreatePersonValidator.cs class, validation is to check if the date is in the past:

.LessThan (p => DateTime.Now)

Question

How to customize the error message without using DataAnnotations (using FluentValidator).

Answer 1

public CreatePersonValidator()
{
    RuleFor(courseOffering => courseOffering.StartDate)
       .Must(BeAValidDate).WithMessage("Start date is required");

    //....
}

private bool BeAValidDate(DateTime date)
{
    return !date.Equals(default(DateTime));
}