MVC3 - passing NEW-LINE to ModelState.AddModelError

Question

When an error occurs on the back-end, the MVC controller returns a message via the
ModelState.AddModelError("", "message");

I would like to have that 'message' display in 2 lines, so I would like to put a "\r\n"
or a "<br />" in between.

I'm using Razor to display the Message using @Html.ValidationSummary();
But the HTML Output from the View displays that as <br/>

What is the best way to pass New-Lines on a message and get it interpreted into a real
tag at the HTML output level?

================================
Controller code:

ModelState.AddModelError("", "Line one <br /> Line two.");
return Request.IsAjaxRequest() ? (ActionResult) PartialView("ViewName", model) 
            : View(model);

View code:

@using (Ajax.BeginForm("Index", "Home", new AjaxOptions { UpdateTargetId = "tv" })) 
{
    @if (Html.ValidationSummary() != null)
        @Html.Raw(Server.HtmlDecode(Html.ValidationSummary(true).ToString()))   

    ....
}

The ValidationSummary helper automatically HTML encodes the message. You will have to write a custom helper if you want to achieve that. — Darin Dimitrov, Nov 16 '11 at 18:23

score 16 · Accepted Answer · answered Nov 16 '11 at 21:23

The ValidationSummary helper HTML encodes error messages and this is by design. It means that you cannot use HTML tags as they will be encoded. So you could write a custom helper which doesn't encode:

public static class ValidationExtensions
{
    public static IHtmlString MyValidationSummary(this HtmlHelper htmlHelper)
    {
        var formContextForClientValidation = htmlHelper.ViewContext.ClientValidationEnabled ? htmlHelper.ViewContext.FormContext : null;
        if (htmlHelper.ViewData.ModelState.IsValid)
        {
            if (formContextForClientValidation == null)
            {
                return null;
            }
            if (htmlHelper.ViewContext.UnobtrusiveJavaScriptEnabled)
            {
                return null;
            }
        }

        var stringBuilder = new StringBuilder();
        var ulBuilder = new TagBuilder("ul");

        ModelState modelState;
        if (htmlHelper.ViewData.ModelState.TryGetValue(htmlHelper.ViewData.TemplateInfo.HtmlFieldPrefix, out modelState))
        {
            foreach (ModelError error in modelState.Errors)
            {
                string userErrorMessageOrDefault = error.ErrorMessage;
                if (!string.IsNullOrEmpty(userErrorMessageOrDefault))
                {
                    var liBuilder = new TagBuilder("li");
                    liBuilder.InnerHtml = userErrorMessageOrDefault;
                    stringBuilder.AppendLine(liBuilder.ToString(TagRenderMode.Normal));
                }
            }
        }

        if (stringBuilder.Length == 0)
        {
            stringBuilder.AppendLine("<li style=\"display:none\"></li>");
        }
        ulBuilder.InnerHtml = stringBuilder.ToString();

        TagBuilder divBuilder = new TagBuilder("div");
        divBuilder.AddCssClass(htmlHelper.ViewData.ModelState.IsValid ? HtmlHelper.ValidationSummaryValidCssClassName : HtmlHelper.ValidationSummaryCssClassName);
        divBuilder.InnerHtml = ulBuilder.ToString(TagRenderMode.Normal);
        if (formContextForClientValidation != null)
        {
            if (!htmlHelper.ViewContext.UnobtrusiveJavaScriptEnabled)
            {
                divBuilder.GenerateId("validationSummary");
                formContextForClientValidation.ValidationSummaryId = divBuilder.Attributes["id"];
                formContextForClientValidation.ReplaceValidationSummary = false;
            }
        }
        return new HtmlString(divBuilder.ToString(TagRenderMode.Normal));
    }
}

and then:

@Html.MyValidationSummary()

It is the following line in our custom helper which explicitly doesn't HTML encode:

liBuilder.InnerHtml = userErrorMessageOrDefault;

In the original helper it looks like this:

liBuilder.SetInnerText(userErrorMessageOrDefault);

If I got a $ for every time one of your answers helped me out Darin, I wouldn't be working right now. — Chris, Oct 26 '12 at 03:19

counsellorben · Answer 2 · 2011-11-16T18:46:00.713

12

Try wrapping the validation summary in an Html.Raw and a Server.HtmlDecode, like so:

@Html.Raw(Server.HtmlDecode(Html.ValidationSummary().ToString()))

edited Nov 16 '11 at 18:46

answered Nov 16 '11 at 18:36

counsellorben

10,924
3
40
38

When I put that line of code, it does not even show the partial view. It gives me a "500 internal server error". – SF Developer Nov 16 '11 at 18:40
I revised my answer. I tested the revised code, and it returned the error message with a line break when I had `
` in the error message. – counsellorben Nov 16 '11 at 18:47
The problem is with @Html.ValidationSummary; I tried replacing it with ViewBag.Temp ..and it did work. So we need to find out how to make the ValidationSummary work before we start thinking to replace it totally. – SF Developer Nov 16 '11 at 18:48
Maybe I have the Validation inside a Ajax.BeginForm. would that be the difference ? – SF Developer Nov 16 '11 at 18:49
Please edit your question, and add the view you are trying to return. – counsellorben Nov 16 '11 at 18:54
@Filu, there's not much you could do with ValidationSummary. As I said in my comment it HTML encodes messages by default and this is by design. So you need to write a custom helper for this. – Darin Dimitrov Nov 16 '11 at 21:02
2

Works for me! `@Html.Raw(Server.HtmlDecode(Html.ValidationSummary(true, "", new { @class = "text-danger" }).ToString()))` – Ray Linder Nov 23 '16 at 21:24
@DarinDimitrov your custom helper is great thanks - but Coundsellorben and Ray are correct: this solution works too. A good quick option for someone only using it once or twice in a project. Thanks. – MemeDeveloper Mar 19 '19 at 00:44

ADH · Answer 3 · 2015-03-25T21:00:12.197

4

Controller:

ModelState.AddModelError("MyError", "Line 1" + Environment.NewLine + "Line 2");

Razor:

<span style="white-space: pre-line">@Html.ValidationSummary()</span>

edited Mar 25 '15 at 21:00

answered Mar 25 '15 at 20:39

ADH

2,971
6
34
53

2

inserting Environment.NewLine as proposed here, did not work for me. – Mario Levesque Mar 08 '17 at 19:24
@levteck Any thoughts on why it would work for me and not you? – ADH Mar 09 '17 at 19:37
2

@MarioLevesque Worked for me. Make sure you stylize the `span` element like in the example. – Lukas Jun 01 '20 at 18:56

score 1 · Answer 4 · answered Dec 18 '14 at 19:41

This is a late answer, however this is the top result when I Google, so my solution may help someone.

I went around the problem and added a separate line for each error message line. Displays beautifully.

Controller code:

    public ActionResult Edit(EditModel model)
    {
            try
            {
                //... do update
            }
            catch (Exception ex)
            {
                if (ex.Message.Contains(Environment.NewLine))
                {
                    var messages = ex.Message.Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
                    foreach (var message in messages)
                    {
                        this.ModelState.AddModelError(string.Empty, message);
                    }
                }
                else
                {
                    this.ModelState.AddModelError(string.Empty, ex.Message);
                }
            }
        //...

        return this.View(model);
    }

This doesn't work if you use the first param key in AddModelError to refer to an input — marianotigre, Oct 23 '18 at 16:13

MVC3 - passing NEW-LINE to ModelState.AddModelError

4 Answers4

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