Fluent Validation When Clause

Question

I'm developing an ASP.Net MVC 5 web application and I'm using FluentValidation (https://github.com/JeremySkinner/FluentValidation) for validation. I am having trouble with the .When() clause in that I can't get it working. However, I can get the likes of the .NotEmpty() and .Length() clauses working.

This is my Viewmodel class

[Validator(typeof(ViewModelEmployerValidator))]
public class ViewModelEmployer
{
    public string CurrentLineManagerEmail { get; set; }
    public string NewLineManagerEmail { get; set; }
}

public class ViewModelEmployerValidator : AbstractValidator<ViewModelEmployer>
{
    public ViewModelEmployerValidator()
    {
        RuleFor(x => x.NewLineManagerEmail).NotEmpty().When(x => x.CurrentLineManagerEmail == "").WithMessage("Please enter your new Line Manager Email");
    }
}

My Razor View

<div>
    <div class="form-group">
        @Html.TextBoxFor(model => model.CurrentLineManagerEmail, new { @class = "form-control", placeholder = "Current Line Manager Email" })
        @Html.ValidationMessageFor(model => model.CurrentLineManagerEmail)
    </div>
</div>

<div>
    <div class="form-group">
        @Html.TextBoxFor(model => model.NewLineManagerEmail, new { @class = "form-control", placeholder = "New Line Manager Email" })
        @Html.ValidationMessageFor(model => model.NewLineManagerEmail)
    </div>
</div>

When the user submits the form, even when the text box CurrentLineManagerEmail is left empty, the .When() validation does that pick up the rule and ask the user to enter their new line manager email.

However, as stated above, the likes of .NotEmpty() and .Length() or their own work fine. It's only when I add the .When() clause that the validation seems to fail.

Can anyone please help?

Thanks.

Are you expecting client side validation (FluentValidation does not support .When() with jquery.validate.unobtrusive.js) — user3559349
When does not work at client side, but on server side, I didn't have any problem with it — Adil Mammadov
@StephenMuecke Hi Stephen. Yes I was expecting Client validation with the .When() . Is there anyway around this? — tcode
Short answer is no. From the docs Note that FluentValidation will also work with ASP.NET MVC's client-side validation, but not all rules are supported. For example, any rules defined using a condition (with When/Unless), custom validators, or calls to Must will not run on the client side. — user3559349
Have a look at this link. Only some of validations are supported at client side by default. You can write custom code to support other validation rules also, but I do not think that you can do it for When. — Adil Mammadov

Rik Rik · Accepted Answer · 2016-10-17T11:20:29

FluentValidation has limited support for client-side validation:

Note that FluentValidation will also work with ASP.NET MVC's client-side validation, but not all rules are supported. For example, any rules defined using a condition (with When/Unless), custom validators, or calls to Must will not run on the client side. The following validators are supported on the client:

NotNull/NotEmpty

Matches (regex)

InclusiveBetween (range)

CreditCard

Email

EqualTo (cross-property equality comparison)

Length

(From https://fluentvalidation.codeplex.com/wikipage?title=mvc)

Fluent Validation When Clause

1 Answers