Dynamically assembling bundles from controller - asp.net-mvc

Question

I updating a custom CMS to be able to support multiple sites with different skins. I want to be able to store the skin dependent css files in a the database then load them in to a bundle once the CMS has determined which site is being loaded. This is what I have so far:
Controller:
public void loadResources(int portal_ID)
{
List<Portal_Res> res = cms.Portal_Resources.Where(r => r.portal_id == portal_ID).ToList<Portal_Res>();
BundleCollection portal_bundles = new BundleCollection();
List<Portal_Res> dsk_css = res.Where(r => r.type == "Desktop CSS").ToList<Portal_Res>();
StyleBundle bdl_dsk_css = new StyleBundle("~/Content/prtl_dsk_css");
if (dsk_css.Count > 0)
{
foreach (Portal_Res r in dsk_css)
{
bdl_dsk_css.Include(r.path);
}
}
portal_bundles.Add(bdl_dsk_css);
BundleConfig.RegisterBundles(portal_bundles);
}
View:
#Styles.Render("~/Content/prtl_dsk_css")
Rendered result:
<link href="/Content/prtl_dsk_css" rel="stylesheet"/>
None of the css files added to the bundle render in the page. Have checked that they are definitely being added to the bundle when the controller runs but not being rendered one the page.
Any ideas?
EDIT: Have inserted a breakpoint in the view and new bundles are not being pulled in with rest of them when the View renders. Don't know why.

Answer 1

Found solution:
public void loadResources(int portal_ID)
{
List<Portal_Res> res = cms.Portal_Resources.Where(r => r.portal_id == portal_ID).ToList<Portal_Res>();
List<Portal_Res> dsk_css = res.Where(r => r.type == "Desktop CSS").ToList<Portal_Res>();
StyleBundle bdl_dsk_css = new StyleBundle("~/Content/prtl_dsk_css");
if (dsk_css.Count > 0)
{
foreach (Portal_Res r in dsk_css)
{
bdl_dsk_css.Include(r.path);
}
}
BundleTable.Bundles.Add(bdl_dsk_css);
BundleConfig.RegisterBundles(BundleTable.Bundles);
}
Had to use BundleTable instead of new BundleCollection
Hope this is useful to someone else.