MVC4 StyleBundle: Can you add a cache-busting query string in Debug mode?

Question

I\'ve got an MVC application and I\'m using the StyleBundle class for rendering out CSS files like this:

bundles.Add(new StyleBundle(\"~/bundles         


        

Answer 1

You can create a custom IBundleTransform class to do this. Here's an example that will append a v=[filehash] parameter using a hash of the file contents.

public class FileHashVersionBundleTransform: IBundleTransform
{
    public void Process(BundleContext context, BundleResponse response)
    {
        foreach(var file in response.Files)
        {
            using(FileStream fs = File.OpenRead(HostingEnvironment.MapPath(file.IncludedVirtualPath)))
            {
                //get hash of file contents
                byte[] fileHash = new SHA256Managed().ComputeHash(fs);

                //encode file hash as a query string param
                string version = HttpServerUtility.UrlTokenEncode(fileHash);
                file.IncludedVirtualPath = string.Concat(file.IncludedVirtualPath, "?v=", version);
            }                
        }
    }
}

You can then register the class by adding it to the Transforms collection of your bundles.

new StyleBundle("...").Transforms.Add(new FileHashVersionBundleTransform());

Now the version number will only change if the file contents change.