ASP.NET MVC - Add XHTML into validation error messages

Question

Just starting with ASP.Net MVC and have hit a bit of a snag regarding validation messages. I've a custom validation attribute assigned to my class validate several properties on my model.

When this validation fails, we'd like the error message to contain XHTML mark-up, including a link to help page, (this was done in the original WebForms project as a ASP:Panel).

At the moment the XHTML tags such as "< a >", in the ErrorMessage are being rendered to the screen. Is there any way to get the ValidationSummary to render the XHTML markup correctly? Or is there a better way to handle this kind of validation?

Thanks

Jonathan · Accepted Answer · 2010-11-22 09:26:43Z

7

Here's a short-term fix that uses HtmlDecode() to reverse the encoding. Works for me.

(Couldn't be bothered rebuilding the whole Validation object model.)

public static class ValidationExtensions
{
  public static MvcHtmlString ValidationMessageHtmlFor<TModel, TProperty>(
    this HtmlHelper<TModel> htmlHelper,
    Expression<Func<TModel, TProperty>> expression)
  {
    return new MvcHtmlString(
      HttpUtility.HtmlDecode(
        htmlHelper.ValidationMessageFor<TModel, TProperty>(
        expression, 
        null, 
      ((IDictionary<string, object>)new RouteValueDictionary()))
        .ToHtmlString()));
  }
}

answered Nov 22, 2010 at 9:26

Jonathan

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1 Comment

Arnoud Over a year ago

Thank you, works great. For anyone else using this answer: don't forget to include using System.Web.Mvc.Html; at the top of your file or it won't find the htmlHelper.

tvanfosson · Accepted Answer · 2010-03-21 13:06:38Z

2

I'm pretty sure that the default validation message helpers HTML encode any message that you might have in your attribute. My suggestion would be to use the source code available on CodePlex as a starting point to write your own HtmlHelper extension that doesn't do HTML encoding on the error string. You want to look in the System.Web.Mvc.Html namespace for the ValidationExtensions.cs file.

answered Mar 21, 2010 at 13:06

tvanfosson

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1 Comment

Neil Over a year ago

Ultimately it uses the following method I think: public void SetInnerText(string innerText) { this.InnerHtml = HttpUtility.HtmlEncode(innerText); } But as I'm using ValidationSummary to show messsages, I guess this means I can't use it for messages that contain XHTML. I guess I could roll my own ValidationSummary, using the source in the System.Web.Mvc.Html namespace but remove encoding call?

Mark · Accepted Answer · 2011-02-10 11:18:04Z

2

I ended up just taking the ValidationSummary output, and just HtmlDecode it.

Works great with ModelState errors in html, and I don't have to make my own ValidationSummary.

public static MvcHtmlString ValidationSummaryNoEncode(this HtmlHelper htmlHelper)
{
    string validationSummaryOutput = htmlHelper.ValidationSummary().ToHtmlString();

    string decodedValidationSummaryOutput = HttpUtility.HtmlDecode(validationSummaryOutput);

    return MvcHtmlString.Create(decodedValidationSummaryOutput);
}

answered Feb 10, 2011 at 11:18

Mark

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Comments

Robert P · Accepted Answer · 2013-09-07 18:22:59Z

0

You can also use the Html.Raw and HttpUtility.HtmlDecode helper methods in a view to render validation messages that contain HTML markup. Here's a simple example:

Model:

[Required(ErrorMessage = "This message contains <b>HTML markup</b> code.")]
public string MyProperty{ get; set; }

View:

@Html.Raw(HttpUtility.HtmlDecode(Html.ValidationMessageFor(x => x.MyProperty).ToHtmlString()))

edited Sep 7, 2013 at 18:22

answered Sep 7, 2013 at 18:09

Robert P

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Neil · Accepted Answer · 2010-04-10 12:08:07Z

-1

OK, thanks to tvanfosson for the suggestion about looking at the source code.

I essentially rolled my own "Html.ValidationSummaryXHTML" helper that didn't HtmlEncode any error message in ModelState, just deferred to "InnerHtml".

Works a treat!

edited Apr 10, 2010 at 12:08

answered Mar 21, 2010 at 13:53

Neil

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1 Comment

tvanfosson Over a year ago

Usu. you'd want to comment on your question or edit it instead of adding an answer. Also, the way the system works is you upvote answers that are helpful (once you get 15 rep) and accept (use the checkmark) the answer that best solves your problem. All of this is in the FAQ (see link at top of page). You can accept your own answer if it is the best, but you have to wait a couple of days. Welcome to the site.

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