C# – Using ASP.NET 4.5 Bundling & a CDN (eg. CloudFront)

amazon-cloudfrontasp.net-4.5bundling-and-minificationc

ASP.NET 4.5 has a great new bundling feature and appears to have some support for use of CDNs. The example given by Microsoft for use of the bundling feature with a CDN is this

public static void RegisterBundles(BundleCollection bundles)
{
  //bundles.Add(new ScriptBundle("~/bundles/jquery").Include(
  //            "~/Scripts/jquery-{version}.js"));

  bundles.UseCdn = true;   //enable CDN support

  //add link to jquery on the CDN
  var jqueryCdnPath = "http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.7.1.min.js";

  bundles.Add(new ScriptBundle("~/bundles/jquery",
            jqueryCdnPath).Include(
            "~/Scripts/jquery-{version}.js"));

  // Code removed for clarity.
}

Which seems to suggest that you need tell it explicitly the path to your file on the CDN.

The CloudFront CDN (and I presume many others) gives you a subdomain which mirrors your own. When you hit http://uniquesubdomain.cloudfront.net/js/myfile.js?v=1 it serves up http://mydomain.com/js/myfile.js?v=1

This way you can simply prefix all your links with http://uniquesubdomain.cloudfront.net/ and your files are server from CloudFront.

Is the ASP.NET 4.5 bundling feature compatible with this type of CDN? Is there a built-in way to have the bundling feature prefix all its links with your CDN domain?

Eg.

bundles.UseCdn = true;
var myBundle= new ScriptBundle("~/bundles/js", "https://uniquedomain.cloudfront.net/");
myBundle.Include("~/js/file1.js");
myBundle.Include("~/js/file2.js");

would cause

    <script src="https://uniquedomain.cloudfront.net/bundles/js?v=6y-qVPSK3RYOYHfPhOBDd92H4LjEjs-D3Hh2Yml6CXA1"></script>

Best Answer

This functionality is not built-in, but is possible with a couple of small helper methods. Here's what I'm using right now:

public static class Cdn
{
    private const string CdnRoot = "//cloudfrontdomainhere.com";

    private static bool EnableCdn
    {
        get
        {
            bool enableCdn = false;
            bool.TryParse(WebConfigurationManager.AppSettings["EnableCdn"], out enableCdn);
            return enableCdn;
        }
    }

    public static IHtmlString RenderScripts(string bundlePath)
    {
        if (EnableCdn)
        {
            string sourceUrl = CdnRoot + Scripts.Url(bundlePath);
            return new HtmlString(string.Format("<script src=\"{0}\"></script>", sourceUrl));
        }

        return Scripts.Render(bundlePath);
    }

    public static IHtmlString RenderStyles(string bundlePath)
    {
        if (EnableCdn)
        {
            string sourceUrl = CdnRoot + Styles.Url(bundlePath);
            return new HtmlString(string.Format("<link href=\"{0}\" rel=\"stylesheet\" />", sourceUrl));
        }

        return Styles.Render(bundlePath);
    }
}

Note that I have my own configuration setting called EnableCdn in the appSettings section of my config file. When called from a Razor view, this produces the correct ouput, which appends the CDN domain onto the paths.

In your Razor files just do Cdn.RenderScripts("~/pathtoscriptbundle")

Related Solutions

C# – Should ‘using’ directives be inside or outside the namespace

There is actually a (subtle) difference between the two. Imagine you have the following code in File1.cs:

// File1.cs
using System;
namespace Outer.Inner
{
    class Foo
    {
        static void Bar()
        {
            double d = Math.PI;
        }
    }
}

Now imagine that someone adds another file (File2.cs) to the project that looks like this:

// File2.cs
namespace Outer
{
    class Math
    {
    }
}

The compiler searches Outer before looking at those using directives outside the namespace, so it finds Outer.Math instead of System.Math. Unfortunately (or perhaps fortunately?), Outer.Math has no PI member, so File1 is now broken.

This changes if you put the using inside your namespace declaration, as follows:

// File1b.cs
namespace Outer.Inner
{
    using System;
    class Foo
    {
        static void Bar()
        {
            double d = Math.PI;
        }
    }
}

Now the compiler searches System before searching Outer, finds System.Math, and all is well.

Some would argue that Math might be a bad name for a user-defined class, since there's already one in System; the point here is just that there is a difference, and it affects the maintainability of your code.

It's also interesting to note what happens if Foo is in namespace Outer, rather than Outer.Inner. In that case, adding Outer.Math in File2 breaks File1 regardless of where the using goes. This implies that the compiler searches the innermost enclosing namespace before it looks at any using directive.

C# – Get property value from string using reflection

 public static object GetPropValue(object src, string propName)
 {
     return src.GetType().GetProperty(propName).GetValue(src, null);
 }

Of course, you will want to add validation and whatnot, but that is the gist of it.

Best Answer

Related Solutions

C# – Should ‘using’ directives be inside or outside the namespace

C# – Get property value from string using reflection

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