Check if Validation Message Exists ASP.Net MVC 5

Question

Is there a way to check if Validation Message exists for a particualr field in ASP.Net MVC 5. I need to check this in Razaor form

Currently is IsNullOrEmpty but i think ValidationMessage does return some html tags even if there are no validation errors ?

I need to show a div only if a Validation Message Exists i.e. validation has failed for that for a particaulr field.

score 44 · Answer 1 · edited Sep 09 '15 at 11:36

44

You can access the ModelState through a property of ViewData in order to check for validation errors before outputting any HTML:

 @if(!ViewData.ModelState.IsValid) {
      @Html.ValidationMessageFor(...)
 }

Edit: or, if you're wanting to check a specific property:

 @if(ViewData.ModelState["PropertyName"] != null && ViewData.ModelState["PropertyName"].Errors.Any()) {
       @Html.ValidationMessageFor(...)
  }

edited Sep 09 '15 at 11:36

Joseph Woodward

9,191
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answered Jul 29 '14 at 16:30

Ben Griffiths

1,676
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1

If the property key doesn't exist then you'll receive a `NullReferenceException`, so don't forget to check for null before trying to access the `Errors` property. – Joseph Woodward Sep 09 '15 at 11:37

score 5 · Answer 2 · answered Jul 29 '14 at 16:19

5

This is the span created by @ValidationMessagefor() :

<span class="field-validation-error" data-valmsg-for="FieldName" data-valmsg-replace="true"><span for="FieldName" generated="true" class="">Field name is required.</span></span>

You can just check class "field-validation-error" whether it exists or not.

answered Jul 29 '14 at 16:19

Kartikeya Khosla

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and the best way to do that? – knowledgeseeker Jul 29 '14 at 16:26
@knowledgeseeker as per my knowledge the above answer is most suitable for your functionality because this is the html which ValidationMessageFor() will render in the DOM and this is the easiest way also.. – Kartikeya Khosla Jul 29 '14 at 16:28

score 3 · Answer 3 · answered Dec 15 '15 at 20:39

This is a pretty dumb test, but usually sufficient, and has the added benefit of utilizing Intellisense in Visual Studio:

Create Project/Helpers/HtmlHelper.cs as a new class

using System.Web.Mvc;
using System.Web.Mvc.Html;

namespace Project.Helpers
{
    public static class HtmlHelper
    {
        public static bool HasValidationMessageFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
        {
            var value = htmlHelper.ValidationMessageFor(expression).ToString();

            return value.Contains("field-validation-error");
        }
    }
}

Add that namespace to Views/Web.config:

<configuration>
  <system.web.webPages.razor>
    <pages pageBaseType="System.Web.Mvc.WebViewPage">
      <namespaces>
        <add namespace="Project.Helpers" />

Close and reopen the solution in Visual Studio, which I had to to for VS 2013 or Intellisense didn't pick up the new HTML helper in my Razor views

Use it:

@if (Html.HasValidationMessageFor(model => model.Property))
{
    @* Do stuff *@
}

Kartikeya's answer provided the markup generated by the Html.ValidatorMessageFor(...) method call:

<span class="field-validation-error" data-valmsg-for="FieldName" data-valmsg-replace="true">
    <span for="FieldName" generated="true" class="">
        Field name is required.
    </span>
</span>

(Code formatting, mine)

And as he said, testing for the field-validation-error class name should work fine.

score 2 · Answer 4 · answered Mar 05 '17 at 19:14

a) unknown or general custom added error display (non model property specific)

  if (ViewData.ModelState.Any(x => x.Key == string.Empty))
  {
      @Html.ValidationSummary(true, string.Empty, new { @class = "error")
  }

b) model property specific error display

@Html.ValidationMessageFor(m => m.Email, string.Empty, new { @class = "error" })

score 0 · Answer 5 · answered Jul 26 '17 at 14:11

I created a Html Helper to check if the ModelState is valid, and if has a error on the field, return a string (class name). I could have done this directly on the view, but I like a cleaner view. So, my class:

public static class ErrorHelper
{
    private static string GetPropertyName<TModel, TValue>(Expression<Func<TModel, TValue>> expression)
    {
        // Get field name
        // Code from: https://stackoverflow.com/a/2916344/4794469
        MemberExpression body = expression.Body as MemberExpression;
        if (body != null) return body.Member.Name;

        UnaryExpression ubody = expression.Body as UnaryExpression;
        if (ubody != null) body = ubody.Operand as MemberExpression;

        return body?.Member.Name;
    }

    public static MvcHtmlString ReturnOnError<TModel, TValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TValue>> expression, string @class)
    {
        var propertyName = GetPropertyName(expression);
        if (propertyName == null)
            return MvcHtmlString.Empty;

        if (htmlHelper.ViewData.ModelState.IsValid || !htmlHelper.ViewData.ModelState.ContainsKey(propertyName))
            return MvcHtmlString.Empty;

        return htmlHelper.ViewData.ModelState[propertyName].Errors.Any()
            ? MvcHtmlString.Create(@class)
            : MvcHtmlString.Empty;
    }
}

Imports:

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Web.Mvc;

How to use in the view:

<div class="form-group @Html.ReturnOnError(m => m.Name, "has-error")">
    ...
</div>

My original answer: https://stackoverflow.com/a/45329194/4794469

Check if Validation Message Exists ASP.Net MVC 5

5 Answers5