How to dynamically change master page's master page?

Question

I am trying to change the master page dynamically, and although it's easy to do from a content page (overriding OnPreInit), there is no such event for a master page. Is it possible to introduce this event somehow?

UPDATE: I got halfway there by going via the PreInit of the pages at the bottom of the ladder, turns out you can do things like base.Master.MasterPageFile = "/master.Master";, but for some reason this doesn't load the stuff in the header of the top-most master page, namely stylesheets.

Answer 1

Quoting from: Can I change a nested master page's master dynamically?

Just tested this and it works from the PreInit of the Page that is using the nested MasterPage. protected void Page_PreInit(object sender, EventArgs e)
{
this.Master.MasterPageFile = "/Site2.Master";
}

Obviously you will need to ensure that the ContentPlaceholderIds are consistent across the pages you are swapping between.

Answer 2

If you overrode the MasterPageClass and added your own onPreInit you might could do it, but I don't think even that would work. There's definitely no construct for it according to Reflector, nothing to even override, altho since it inherits UserControl then there's always OnInit ... alternately you could attempt to override get_Master() but that might not work either ...

Answer 3

Use the masterpage constructor.

Answer 4

Let's say you want to use a different master page without a menu, pass query string NoMenu.

protected void Page_PreInit(object sender, EventArgs e)
 {
   //You'll go through infinite loop if you do not check if we already have the new master page, this will switch to different master page if requested without a menu for example
   if (Request.QueryString["NoMenu"] != null && this.MasterPageFile != "/MasterPageNoMenu.master")
    {
        this.MasterPageFile = "/MasterPageNoMenu.master";

        base.OnPreInit(e); 
    }
}