Dropdownlist Asp.net mvc

Question

I have a product that can be registered in 2 stores A and B if I have already registered in A how do pro Dropdownlist show me only show option B next time it is in register? what would be the logic? using Entityframework and Linq?

[HttpGet]
public IActionResult Create(string businessId)
{
        var marketRest = new Rest
                             .MarketplaceRest(_appSettings.WebApiUrl, _appKeyBase64);

        var registerViewModel = new RegisterMarketPlaceViewModel
        {
            BusinessId = businessId,

        };
        registerViewModel.MarketNameSelectList = 
                registerViewModel.GetMarketplaceSelectList(marketRest, _memoryCache);

        return View(registerViewModel);
}