Make ASP.NET bundling specify media=screen for CSS bundle

问题

I'm just trying out ASP.NET 4.5 bundling and minification, and ran into an issue.

I've got around 10 css files, of which 2 were originally referenced in the layout using the attribute media="screen".

Since the syntax for adding a css to the bundle does not let you specify that such attribute should be added (makes sense, since the attribute would apply for the whole bundle), I was hoping to see an overload of @Styles.Render that would allow me to specify html attributes, like in other Html helpers, but there is none.

There is an ugly solution, in which since I know the url of the bundle created, i could just craft the tag myself, but I'd lose the caching mechanism that is handled by ASP.NET by allowing it to render the tag itself.

Is there a way to do this, am I missing something? Or is this just an oversight of the design team?

回答1:

I've found a more elegant solution.

I'm using the Styles.RenderFormat(format, bundle).

I have a BundlesFormats class with a property called PRINT and I use it like so:

public class BundlesFormats
{
    public const string PRINT = @"<link href=""{0}"" rel=""stylesheet"" type=""text/css"" media=""print"" />";
}

And in the cshtml:

@Styles.RenderFormat(BundlesFormats.PRINT, "~/bundles/Content/print")

回答2:

Well, it's an ugly hack, but hopefully the team will add a built-in way to do it in the next release.

This is how I solved it, maintaining the caching string and still being able to add the media attribute to the tag.

@{
    var cssMediaBundleUrl = BundleTable.Bundles.ResolveBundleUrl("~/stylesheets/mediacss", true);
}
<link href="@cssMediaBundleUrl" rel="stylesheet" type="text/css" media="screen" />

Guess I can turn this into an Html helper, will do that later and edit.

回答3:

Another option to solve this issue, without compromising the debug ability, could be:

public static IHtmlString Render(string path, IDictionary<string, object> htmlAttributes)
{
    var attributes = BuildHtmlStringFrom(htmlAttributes);

#if DEBUG
    var originalHtml = Styles.Render(path).ToHtmlString();
    string tagsWithAttributes = originalHtml.Replace("/>", attributes + "/>");
    return MvcHtmlString.Create(tagsWithAttributes);
#endif

    string tagWithAttribute = string.Format(
        "<link rel=\"stylesheet\" href=\"{0}\" type=\"text/css\"{1} />", 
        Styles.Url(path), attributes);

    return MvcHtmlString.Create(tagWithAttribute);
}

What I'm doing is just appending the given html attributes to the end of the tags (on debug mode) or to the end of the only link tag (when minification/bundling are enabled).

The usage in views:

@Bundles.Render("~/css/print", new { media = "print" })

The rest of the code:

public static IHtmlString Render(string path, object htmlAttributes)
{
    return Render(path, new RouteValueDictionary(htmlAttributes));
}

private static string BuildHtmlStringFrom(IEnumerable<KeyValuePair<string, object>> htmlAttributes)
{
    var builder = new StringBuilder();

    foreach (var attribute in htmlAttributes)
    {
        builder.AppendFormat(" {0}=\"{1}\"", attribute.Key, attribute.Value);
    }

    return builder.ToString();
}

I've wrote a blog post about this subject: http://danielcorreia.net/blog/quick-start-to-mvc4-bundling/

回答4:

Unfortunately there isn't a great way to hook into how the tags are rendered currently, we thought about adding a hook so you could add your own method to render each script/style tag. It sounds like we do need to do that. Should be pretty simple to add, I'll create a work item to enable this scenario...

As a temporary workaround, if you are willing to lose the debug/release functionality that Styles.Render gives you, you can render a reference to the bundle using Styles.Url which would give you just the bundle url, you can embed that inside your own tag.

回答5:

Why not just use @media print? Check out http://www.phpied.com/5-years-later-print-css-still-sucks/

回答6:

Web Forms Solution

In BundleConfig.cs:

//Print css must be a separate bundle since we are going to render it with a media=print
Bundles.Add(new StyleBundle("~/bundles/printCSS").Include("~/Content/Print.css"));

Master Page:

<asp:Literal runat="server" ID="litCssPrint" />

Master Page Code File:

litCssPrint.Text = Styles.RenderFormat(@"<link href=""{0}"" rel=""stylesheet"" type=""text/css"" media=""print"" />", "~/bundles/printCSS").ToHtmlString();

回答7:

So complicated, why not to use:

bundles.Add<StylesheetBundle>("~/Css/site.css", b => b.Media = "screen");

?

来源：https://stackoverflow.com/questions/12042248/make-asp-net-bundling-specify-media-screen-for-css-bundle