Layout page in dot net core not showing changes on click from Index page

Question

I have menus on Layout page and I need to make them enabled on click of button which is there on Index view On Index button click I have called controller action which sets the flag using view bag and then I am enabling menu if the flag is set by checking condition on layout page, condition is checked correctly but still menu is not enabled, but if I am clicking any other button then menu is enabling

Layout.cshtml

 @if (@ViewBag.Enable == "true" || Context.Session.GetString("CustomerCode") == null)
                        {
                            <a href="#OCLegacy" data-toggle="collapse" aria-expanded="false" style="color:gray" class="bg-dark list-group-item list-group-item-action flex-column align-items-start disabled">
                                <div class="d-flex w-100 justify-content-start align-items-center">
                                    <span class="bi bi-diamond-fill fa-fw mr-3"></span>
                                    <span class="menu-collapsed">OC-Legacy</span>
                                    <span class="submenu-icon ml-auto"></span>
                                </div>
                            </a>
                        }

Index.cshtml

 <a asp-action="Index" style="align-self:self-end"  data-id="@customer.CustomerCode"
                          
                           class="btn btn-primary ManageSelect">

calling index action from controller

Answer 1

Here is a demo with ViewBag.Enable. pass @customer.CustomerCode to action,if the it is not null,set ViewBag.Enable to true.Else,set ViewBag.Enable to false.If ViewBag.Enable is true,male the menu enable. Layout:

@if (@ViewBag.Enable != "true")
            {
                <a href="#OCLegacy" data-toggle="collapse" aria-expanded="false" style="color:gray" class="bg-dark list-group-item list-group-item-action flex-column align-items-start disabled">
                    <div class="d-flex w-100 justify-content-start align-items-center">
                        <span class="bi bi-diamond-fill fa-fw mr-3"></span>
                        <span class="menu-collapsed">OC-Legacy</span>
                        <span class="submenu-icon ml-auto"></span>
                    </div>
                </a>
            }
            else { 
                <a href="#OCLegacy" data-toggle="collapse" aria-expanded="false" style="color:gray" class="bg-dark list-group-item list-group-item-action flex-column align-items-start">
                    <div class="d-flex w-100 justify-content-start align-items-center">
                        <span class="bi bi-diamond-fill fa-fw mr-3"></span>
                        <span class="menu-collapsed">OC-Legacy</span>
                        <span class="submenu-icon ml-auto"></span>
                    </div>
                </a>
            }

Index(asp-route-id will pass @customer.CustomerCode as a parameter id to action):

<a asp-action="Index" style="align-self:self-end" asp-route-id="@customer.CustomerCode" data-id="@customer.CustomerCode"
                          
                           class="btn btn-primary ManageSelect">

Action:

public IActionResult Index(string id)
{
    if (id != null)
    {
        ViewBag.Enable = "true";
    }
    else
    {
        ViewBag.Enable = "false";
    }
   
    return View();
}

result: