Replace line break characters with <br /> in ASP.NET MVC Razor view

Question

I have a textarea control that accepts input. I am trying to later render that text to a view by simply using:

@Model.CommentText

This is properly encoding any values. However, I want to replace the line break characters with <br /> and I can't find a way to make sure that the new br tags don't get encoded. I have tried using HtmlString but haven't had any luck yet.

Mellow

I presume linebreaks are stored as \n in the database and you want to convert to a <br />? – Guanabana

Yes - just trying to replace \n with <br /> in the view. – Mellow

Answer 1

Use the CSS white-space property instead of opening yourself up to XSS vulnerabilities!

<span style="white-space: pre-line">@Model.CommentText</span>

Jeopardize

quirksmode.org/css/whitespace.html has a good explanation of pre-line (I was only aware of nowrap and pre). – Ufo

actually white-space: pre-wrap; is better since pre-line will mess with your text by grouping white spaces into one space. – Stichometry

@ChtiwiMalek: I certainly agree that you usually want to preserve all white space, but the original question asked about converting linebreaks into <br />s – Jeopardize

Unfortunately this won't work in almost any email client (including Office 2013). – Chromogen

One caveat with this approach is that due to browser bugs the new lines will be lost on copy-paste. See bugzilla.mozilla.org/show_bug.cgi?id=1174452 and code.google.com/p/chromium/issues/detail?id=317365 – Curium

Answer 2

Try the following:

@MvcHtmlString.Create(Model.CommentText.Replace(Environment.NewLine, "<br />"))

Update:

According to marcind's comment on this related question, the ASP.NET MVC team is looking to implement something similar to the <%: and <%= for the Razor view engine.

Update 2:

We can turn any question about HTML encoding into a discussion on harmful user inputs, but enough of that already exists.

Anyway, take care of potential harmful user input.

@MvcHtmlString.Create(Html.Encode(Model.CommentText).Replace(Environment.NewLine, "<br />"))

Update 3 (Asp.Net MVC 3):

@Html.Raw(Html.Encode(Model.CommentText).Replace("\n", "<br />"))

Journal

Oh my GOD, no. What if I decide to comment about some <script>. – Suzette

Thanks - that worked. Was very close but must have been doing the replace too soon or too late. I ended up using this: @MvcHtmlString.Create(Html.Encode(Model.CommentText).Replace("\n", "<br />")) because Environment.NewLine wasn't working right. – Mellow

@thekaido - I recommend that you do all the replacing and encoding in the controller and passing a IHtmlString to the view or creating a custom HtmlHelper that does all this for you. Seeing this line of code in a view can be painful. – Journal

Environment.NewLine doesn't really apply to form posts since browsers usually return just \n instead of \r\n – Receive

For the released version of MVC 3, the suggestion appears to be @Html.Raw(Html.Encode(Model.CommentText).Replace(Environment.NewLine, "<br />")), instead of using MvcHtmlString. At least for display. – Ufo

Environment.NewLine represent "\r\n". If my user entered data using linux or mac, linebreaks are just "\n" or "\r". Isn't there a method somewhere that takes this into account? – Emery

Even with MVC3 this solution looks quite ugly. It's rather long, you have to look twice to be sure everything gets encoded right and you have problems with different kinds of newlines. The CSS-based solution below is much better! – Stephniestepladder

@SandRock: "Some\r\n string\nand a newline ".Replace("\r", "").Replace("\n", "<br />") note that you can safely omit Replace("\r", "") – Methacrylate

@Quandary a bit too brute-force to me. Prefer checking the kind of linebreak before replacing: gist.github.com/3653055 – Emery

Answer 3

Split on newlines (environment agnostic) and print regularly -- no need to worry about encoding or xss:

@if (!string.IsNullOrWhiteSpace(text)) 
{
    var lines = text.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
    foreach (var line in lines)
    {
        <p>@line</p>
    }
}

(remove empty entries is optional)

Cuirassier

Answer 4

Omar's third solution as an HTML Helper would be:

public static IHtmlString FormatNewLines(this HtmlHelper helper, string input)
{
    return helper.Raw(helper.Encode(input).Replace("\n", "<br />"));
}

Curium

Answer 5

Applying the DRY principle to Omar's solution, here's an HTML Helper extension:

using System.Web.Mvc;
using System.Text.RegularExpressions;

namespace System.Web.Mvc.Html {
    public static class MyHtmlHelpers {
        public static MvcHtmlString EncodedReplace(this HtmlHelper helper, string input, string pattern, string replacement) {
            return new MvcHtmlString(Regex.Replace(helper.Encode(input), pattern, replacement));
        }
    }
}

Usage (with improved regex):

@Html.EncodedReplace(Model.CommentText, "[\n\r]+", "<br />")

This also has the added benefit of putting less onus on the Razor View developer to ensure security from XSS vulnerabilities.

---

My concern with Jacob's solution is that rendering the line breaks with CSS breaks the HTML semantics.

Robedechambre

Answer 6

I needed to break some text into paragraphs ("p" tags), so I created a simple helper using some of the recommendations in previous answers (thank you guys).

public static MvcHtmlString ToParagraphs(this HtmlHelper html, string value) 
    { 
        value = html.Encode(value).Replace("\r", String.Empty);
        var arr = value.Split('\n').Where(a => a.Trim() != string.Empty);
        var htmlStr = "<p>" + String.Join("</p><p>", arr) + "</p>";
        return MvcHtmlString.Create(htmlStr);
    }

Usage:

@Html.ToParagraphs(Model.Comments)

Stilla

Answer 7

I prefer this method as it doesn't require manually emitting markup. I use this because I'm rendering Razor Pages to strings and sending them out via email, which is an environment where the white-space styling won't always work.

public static IHtmlContent RenderNewlines<TModel>(this IHtmlHelper<TModel> html, string content)
{
    if (string.IsNullOrEmpty(content) || html is null)
    {
        return null;
    }

    TagBuilder brTag = new TagBuilder("br");
    IHtmlContent br = brTag.RenderSelfClosingTag();
    HtmlContentBuilder htmlContent = new HtmlContentBuilder();

    // JAS: On the off chance a browser is using LF instead of CRLF we strip out CR before splitting on LF.
    string lfContent = content.Replace("\r", string.Empty, StringComparison.InvariantCulture);
    string[] lines = lfContent.Split('\n', StringSplitOptions.None);
    foreach(string line in lines)
    {
        _ = htmlContent.Append(line);
        _ = htmlContent.AppendHtml(br);
    }

    return htmlContent;
}

Ricotta

Answer 8

simply put this inside your div where that text is and it will work.

<p>@Html.Raw(notam.Text.Replace("\r\n", "<br>").Replace("\n", "<br>"))</p>

Leifeste

Thank you for your interest in contributing to the Stack Overflow community. This question already has quite a few answers—including one that has been extensively validated by the community. Are you certain your approach hasn’t been given previously? If so, it would be useful to explain how your approach is different, under what circumstances your approach might be preferred, and/or why you think the previous answers aren’t sufficient. Can you kindly edit your answer to offer an explanation? – Storyteller