Using CDN in ASP.NET MVC bundles

Question

I read the article about bundling and monification, specially about using CDN, but there are some things unclear to me.

Having the example :

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.
}

1. Is there a possibility to use the {version} format of CDN references, like for the "local" ones?

2. What is the point of including in the bundles the already minified version of the script, like jquery-1.7.1.min.js? What if it does not exist? Should it not search if the .min file exist and/or generate it respectively?

Answer 1

using System.Web;
using System.Web.Optimization;

namespace MvcApp
{
    public class BundleConfig
    {
        public static void RegisterBundles(BundleCollection bundles)
        {
            bundles.Add(new ScriptBundle("~/bundles/jquery", "https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js").Include("~/Scripts/jquery-{version}.js"));

            bundles.Add(new ScriptBundle("~/bundles/bootstrap","https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js").Include("~/Scripts/bootstrap.js"));

            bundles.Add(new StyleBundle("~/Content/css", "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css").Include("~/Content/bootstrap.css"));

            BundleTable.EnableOptimizations = true;
            bundles.UseCdn = true;
        }
    }
}

What a lot of developers don't realized is that there is an overload for class constructor of ScriptBundle and StyleBundle, which takes two string parameters, for example for the ScriptBundle it would be ScriptBundle(string, string) and for the StyleBundle it would be StyleBundle(string, string). The first parameter is the virtual path and the second parameter is the cdnPath.

We might be asking yourself, if it takes two parameters, how does MVC know which one to use? Well, the cdn location is used only when the BundleTable.EnableOptimizations property is set to true.

Setting the EnableOptimization property to true tells MVC to use the use the minified version of the file instead of the regular version.

When this property is set to true, and the cdn path is present MVC will use the cdn path instead of the local virtual path.
There is one more property you have to set to true and that is the bundles.UseCdn.
This tells MVC to use the cdn location instead of the local version. If the BundleTable.EnableOptimization is set to false, then the local version is used automatically as a fall back because the cdn version is the minified version.

Read this blog its clear about your think:

http://www.techjunkieblog.com/2015/06/aspnet-mvc-5-configure-bundleconfig.html