it's a code thing: HtmlHelper extension method output unencoded strings in ASP.NET MVC 3.0 Razor views

Friday, February 11, 2011

HtmlHelper extension method output unencoded strings in ASP.NET MVC 3.0 Razor views

In ASP.NET MVC 1.0 when using the <%= tag you had to handle any string html encoding you wanted specifically.

This was changed in ASP.NET 2.0 when generated views introduced the <%: tag which by default would html encode your string. In ASP.NET MVC 2.0 you could use the MvcHtmlString class which allowed you to avoid html encoding a string.

With .NET 4.0 you now have another option for not html encoding strings (for instance from an HtmlHelper extension method used in a ASP.NET MVC 3.0 Razor view). The interface IHtmlString and the implementing class HtmlString allows you to indicate that a string is not to be html encoded.

public static class HtmlHelperExtensions
{
    // .NET 4.0
    public static IHtmlString EmitObjectTagUnencoded(this HtmlHelper htmlHelper, string someValue)
    {
        return new HtmlString(string.Format("<object>{0}</object>", someValue));
    }

    // ASP.NET MVC 2 
    public static MvcHtmlString EmitObjectTagUnencoded2(this HtmlHelper htmlHelper, string someValue)
    {
        return MvcHtmlString.Create(string.Format("<object>{0}</object>", someValue));
    }

    public static string EmitObjectTagEncoded(this HtmlHelper htmlHelper, string someValue)
    {
        return string.Format("<object>{0}</object>", someValue);
    }
}

Using this in a view like the following

<!DOCTYPE html>

<html>
<head>
    <title>Index</title>
</head>
<body>
    <div>
       @Html.EmitObjectTagUnencoded("EmitObjectTagUnencoded")
    </div>
    <div>
       @Html.EmitObjectTagUnencoded2("EmitObjectTagUnencoded2")
    </div>
    <div>
       @Html.EmitObjectTagEncoded("EmitObjectTagEncoded")
    </div>
</body>
</html>

Will yield the following html output

<!DOCTYPE html>

<html>
<head>
    <title>Index</title>
</head>
<body>
    <div>
       <object>EmitObjectTagUnencoded</object>
    </div>

    <div>
       <object>EmitObjectTagUnencoded2</object>
    </div>
    <div>
       &lt;object&gt;EmitObjectTagEncoded&lt;/object&gt;
    </div>
</body>

</html>

Solution file is available here 2011-02-11-IHtmlString.zip

Stack overflow posting discussing the difference between MvcHtmlString and HtmlString

2 comments:

Sebastian Patten said...: Thanks - this just really helped me out :); March 13, 2011
Kenneth Thorman said...: Hi Sebastian

I am glad it was useful.

Regards
Kenneth; March 13, 2011