How to get the database value

I am using Dependency Injection for a Shopping Cart, In the layout page, I want to get a Brand new Price from the database in the ShoppingCart and it does not, it gets the Price from the allready assigned Price from Index of HomeController,

Is there a way I can acomplish this ?

At starup

            services.AddScoped<ShoppingCart>();

In the Controller using the Index, so when I click on the HomeController I belive the yoContext gets assigned the Price value and takes it all the way to the ShoppingCart class

    public class HomeController : Controller
    {
        private yoContext db;
        public HomeController(yoContext context)
        {
            db = context;
        }

        public IActionResult Index()
        {

            foreach(var product in db.Products)
            {
                var prod = db.Products.Single(p => p.productId == product.productId);

                prod.price = // Here I will do other calculations to get the Price that I want                            
                product.price = prod.price ; 
            }
            return View(db.Products.ToList());//Here the db.Products have the new assigned Price 
        }
    }

And in the Service class which is the shoppingCart class Here I get the Product Price assigned from Index and I want to get the Price from the database value instead

    public class ShoppingCart
    {
        private yoContext db;
        public ShoppingCart(yoContext context)
        {
            db = context;
        }
        public decimal GetTotal()
        {
            foreach (var product in db.Products)
            {
                var prod = db.Products.Single(p => p.productId == product.productId);
                product.price = prod.price; // Here I get the assigned value from Index of HomeController, but I want to get the value of the database 
            }
        }

And finally here is the layout page

@inject yo.Services.ShoppingCart cart

                <a asp-action="Index" asp-controller="Cart" class="navbar-brand">
                    @cart.GetQty()
                    <i class="glyphicon glyphicon-shopping-cart "></i>
                    @cart.GetTotal()
                </a>

And I get the wrong Total, because of the assigned value from HomeContrller IActionResult Index