asp.net mvc - MVC bundle client caching

Question

By default a MVC bundle is cached on client for 1 year. Is it possible to set it's client headers manually (for 1 specific bundle)?

What I need is to set custom expire headers for one of my bundles. I can't rely on the "v=hash" querystring because this bundle is for an external website, and they won't change the url pointing to my bundle each time I change it.

What I've tried is to create a custom Bundle class (inherit Bundle) and overridde the GenerateBundleResponse() method. This way I can control the server caching, but the only way of customizing client caching is to set BundleResponse.Cacheability (public, private, nocache etc). But I can't set headers manually. I have access to the BundleContext (and it's HttpContext), but when I set headers on that context, it will have effect for all other requests as well.

Answer 1

Unfortunately there is no way. You can find the reason in the internal implementation of bundling. in the BundleHandler class ProcessRequest calls the ProcessRequest, internal method of the Bundle class and it calls SetHeaders just before the HttpContext.Response.Write. Therefore the client cache is set to one year just before the response write.

Note: BundleHandler is a internal sealed class: internal sealed class BundleHandler : IHttpHandler

In the BundleHandler class:

public void ProcessRequest(HttpContext context)
{
    if (context == null)
    {
        throw new ArgumentNullException("context");
    }
    context.Response.Clear();
    BundleContext context2 = new BundleContext(new HttpContextWrapper(context), BundleTable.Bundles, this.BundleVirtualPath);
    if (!Bundle.GetInstrumentationMode(context2.HttpContext) && !string.IsNullOrEmpty(context.Request.Headers["If-Modified-Since"]))
    {
        context.Response.StatusCode = 304;
    }
    else
    {
        this.RequestBundle.ProcessRequest(context2);
    }
}

In the Bundle class:

internal void ProcessRequest(BundleContext context)
{
    context.EnableInstrumentation = GetInstrumentationMode(context.HttpContext);
    BundleResponse bundleResponse = this.GetBundleResponse(context);
    SetHeaders(bundleResponse, context);
    context.HttpContext.Response.Write(bundleResponse.Content);
}

private static void SetHeaders(BundleResponse bundle, BundleContext context)
{
    if (bundle.ContentType != null)
    {
        context.HttpContext.Response.ContentType = bundle.ContentType;
    }
    if (!context.EnableInstrumentation)
    {
        HttpCachePolicyBase cache = context.HttpContext.Response.Cache;
        cache.SetCacheability(bundle.Cacheability);
        cache.SetOmitVaryStar(true);
        cache.SetExpires(DateTime.Now.AddYears(1));
        cache.SetValidUntilExpires(true);
        cache.SetLastModified(DateTime.Now);
        cache.VaryByHeaders["User-Agent"] = true;
    }
}