update viewbag item in layout.cshtml from partial view

Hi

I have a site that loads different logos etc depending on the URL you enter on


I have the following areas in a _Layout.cshtml file

<title>@ViewBag.PageTitle </title>
   <img id="logo" src="@ViewBag.Logo" />

       <span class="txt-color-white">@ViewBag.Footer</span>

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then in the controller I populate these

     ViewBag.Logo = site.BrandingLogo;
                ViewBag.Title = site.BrandingPageTitle;
                ViewBag.Footer = site.BrandingFooter;

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This all works fine for these
 

public ActionResult Index()
  ..
 return View();

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However its not working for this

public ActionResult LoadGraph(string GroupId)
..
return PartialView(model);

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I assume because its a partial view and not a view?


Can you suggest a way to get this working with a paritial view

Or better yet do this population of the layout in one place rather than every view for different pages?