How to set global viewmodels in ASP .NET Core 3.1? - asp.net-core-mvc

Question

I am new to ASP.NET Core and have some trouble with binding global models and viewmodels to razor views. My application is a mixture of Web API and MVC with razor views.
My goal
When I open an ASP.NET MVC page, I need to instantiate a model by loading it from the database (DbContext service) based on an id received in a cookie. I want to use this model object globally in every view or partial view.
Current Implementation
I can access the cookies in action methods of page controllers, so that I have to load the model from the DbContext in every action method and bind it as viewmodel to target view. This is not practical, because I have to do this in every page controller, because I need that model object on all pages in my navigation pane.
Idea
I think it should be possible to access to Cookies and dbcontext within Startup.cs and bind the model object to _ViewStart.cshtml, so that it is accessible globally in every view or partial view. Even this approach were correct, I do not have any idea how the code would look like. Because I am learning Web-Apps with .NET Core by learning by doing and try and error at the moment. :(
UPDATE
I have a layout page _Layout.cshtml, which includes partial views like the _NavPane.cshtml. My goal is to pass a Model object to the _Layout, which is instantiated via loading from the database (I have a service IMandantRepository for this purpose) and dependent on a cookie.
That model object is needed on every page request. That's why it would be a better practice to load the model object outside the MVC page controllers and pass it to them (what I can not implement technically).
I tried to find a solution by myself and ended up in following interim ugly solution. Following is the content of the _ViewStart file. On the bottom I assign the needed global variables, which I can use in every view or partial view.
This solution has at least two disadvantages:
The model object is possibly loaded redundantly.
Too many program logic in a view file.
#inject MyProject.Data.IMandantRepository mandantRepo
#{
// Main layout template
Layout = "_Layout";
// Define default values
bool showAdminSection = false;
string src = "/images/logos/nologo.png";
// Read cookie value
string currentMandantUid;
Context.Request.Cookies.TryGetValue("currentMandant", out currentMandantUid);
// Load mandant from the database
var thisMandant = mandantRepo.GetMandantByUid(currentMandantUid);
if(thisMandant is Mandant){
src = "data:image/*;base64," + thisMandant.GetBase64Logo();
showAdminSection = thisMandant.Abbr == "AdminMandant";
}
// Assing global variables to ViewData
ViewData["CurrentMandant"] = thisMandant;
ViewData["logoSrc"] = src;
ViewData["showAdminSection"] = showAdminSection;
}

Answer 1

This is an example code in ConfigureService() of Startup.cs. You can register your dbContext class in this way.
services.AddDbContext<BookStoreContext>( options =>
options.UseSqlServer(_configuration.GetConnectionString("DefaultConnection")));