Bundling and Minification

What is Bundle?

A bundle is a logical group of files that is loaded with a single HTTP request. You can create style and script bundle for css and javascripts respectively by calling BundleCollection class Add() method with in BundleConfig.cs file.

Creating Style Bundle

bundles.Add(new StyleBundle("~/Content/css").Include("~/Content/site.min.css",
"~/Content/mystyle.min.css"));

Creating Script Bundle

bundles.Add(new ScriptBundle("~/bundles/jqueryval").Include(
 "~/Scripts/jquery-1.7.1.min.js",
 "~/Scripts/jquery.validate.min.js",
 "~/Scripts/jquery.validate.unobtrusive.min.js"));

Above both the bundles are defined with in BundleConfig class as shown below:

public class BundleConfig
{
 public static void RegisterBundles(BundleCollection bundles)
 {
 bundles.Add(new StyleBundle("~/Content/css").Include("~/Content/site.min.css",
 "~/Content/mystyle.min.css"));
 
bundles.Add(new ScriptBundle("~/bundles/jqueryval").Include(
 "~/Scripts/jquery-1.7.1.min.js",
 "~/Scripts/jquery.validate.min.js",
 "~/Scripts/jquery.validate.unobtrusive.min.js"));
 }
} 

Creating Bundle using the "*" Wildcard Character

"*" wildcard character is used to combines the files that are in the same directory and have same prefix or suffix with its name. Suppose you want to add all the scripts files that exist with in "~/Script" directory and have "jquery" as prefix then you can create bundle like below:

bundles.Add(new ScriptBundle("~/bundles/jqueryval").Include("~/Scripts/jquery*.js"));

You can also add all the css that exist with in "~/Content" directory and have ".css" extension(as suffix) like below:

bundles.Add(new StyleBundle("~/Content/css").Include("~/Content/*.css"));

Registering Bundle

All bundles are registered with in Application_Start event of Global.asax file of you web application.

protected void Application_Start()
{
 BundleConfig.RegisterBundles(BundleTable.Bundles);
 // Other Code is removed for clarity
}

Minification

Minification is technique for removing unnecessary characters (like white space, newline, tab) and comments from the JavaScript and CSS files to reduce the size which cause improved load times of a webpage. There are so many tools for minifying the js and css files. JSMin and YUI Compressor are two most popular tools for minifying the js and css files.

You can also add WebEssentials2012.vsix extension to your VS2012 for minifying the js and css files. This is a great extension for VS2012 for playing with js and css.

Minification with VS2012 and WebEssentials 2012 extension

I would like to share how can you make minify version of you css file using WebEssentials extension and VS2012. This minify version will updated automatically if you will make change in original css file.

 

Performance Optimization with Bundling and Minification

I have done a performance test on a MVC4 application with & without bundling and minification. I have noticed the below result.

Without Bundling and Minification

I have the below css and js files on the layout page and run the application in chrome browser and test no of request and loding time using chrome developer tools as shown below.

<link href="~/Content/Site.css" rel="stylesheet"/>
<link href="~/Content/MyStyle.css" rel="stylesheet"/>
<script src="~/Scripts/jquery-1.7.1.js"></script>
<script src="~/Scripts/jquery-ui-1.8.20.js"></script>
<script src="~/Scripts/jquery.validate.js"></script>
<script src="~/Scripts/jquery.validate.unobtrusive.js"></script>

In this test, I have seen, There are 7 request, total data size is 3.96KB and loading time is approximate 296ms.

With Bundling and Minification

I have run the above application with Bundling and Minification of css and js files and test no of request and loding time using chrome developer tools as shown below.

@Styles.Render("~/Content/css")
@Scripts.Render("~/bundles/jquery")

In this test, I have seen, There are only 3 request, total data size is 2.67KB and loading time is approximate 80ms. In this way by using bundling and minification you have reduced the total no of request, size and loading time.

Enabling Bundling and Minification in debug mode

Bundling and minification doesn't work in debug mode. So to enable this featues you need to add below line of code with in Application_Start event of Global.asax.

protected void Application_Start()
{
 BundleConfig.RegisterBundles(BundleTable.Bundles);
 //Enabling Bundling and Minification
 BundleTable.EnableOptimizations = true; 
 // Other Code is removed for clarity
}

Busting Browser's Cache by Bundling

As you know browsers cache resources based on URLs. When a web page requests a resource, the browser first checks its cache to see if there is a resource with the matched URL. If yes, then it simply uses the cached copy instead of fetching a new one from server. Hence whenever you change the content of css and js files will not reflect on the browser. For this you need to force the browser for refreshing/reloading.

But bundles automatically takes care of this problem by adding a hashcode to each bundle as a query parameter to the URL as shown below. Whenever you change the content of css and js files then a new has code will be generated and rendered to the page automatically. In this way, the browser will see a different url and will fetch the new copy of css and js.