Return Null in View Data in ASP .NET Core

Question

I have a controller and receive correct data from my service and repository( I check it with breakpoint)

 public async Task<IActionResult> Index()
    {
        CountViewModel adminContentCount = await _siteService.AdminContentCount();
        ViewData["UnreadTicketMessage"] = await _siteService.ShowUnReadTicketMessages();

        return View(adminContentCount);
    }

But when sent to view , it returns null

view:

    @{
    ViewData["Title"] = "Index;
 
    IEnumerable<AdminDashboardUnreadMessage> unreadTicketMessagemessages = ViewData["UnreadTicketMessage"] as IEnumerable<AdminDashboardUnreadMessage>;

}

why?