ShoppingCartController.cs

public async Task<IActionResult> AddToCart(int id, CancellationToken requestAborted)
{
    // Retrieve the album from the database
    var addedAlbum = await DbContext.Albums
        .SingleAsync(album => album.AlbumId == id);

    // Add it to the shopping cart
    var cart = ShoppingCart.GetCart(DbContext, HttpContext);

    await cart.AddToCart(addedAlbum);

    await DbContext.SaveChangesAsync(requestAborted);
    _logger.LogInformation("Album {albumId} was added to the cart.", addedAlbum.AlbumId);

    // Go back to the main store page for more shopping
    return RedirectToAction("Index");
}