public ActionResult ListByCategory()
        {
            OnlineShopModel data = new OnlineShopModel();
            data.Products = new List<Product>();
            data.Products = GetProducts();
            return View(data);
        }
        [HttpPost]
        public ActionResult ListByCategory(OnlineShopModel model)
        {
            model.SelectedProducts = new List<string>();
            foreach (var item in model.Products)
            {
                if (item.IsSelected)
                {
                    model.SelectedProducts.Add(item.ProductName);
                }
            }
            return View(model);
        }

@using (Html.BeginForm("ListByCategory", "Home"))
{
                         @for (int i = 0; i < Model.Products.Count; i++)
                         {
                             @Html.CheckBoxFor(m => m.Products[i].IsSelected)
                             @Model.Products[i].ProductName
                             @Html.HiddenFor(m => m.Products[i].ProductId)
                             @Html.HiddenFor(m => m.Products[i].ProductName)
                             <br />
                         }
                        <input type="submit" value="Add To Cart" onclick="location.href='@Url.Action("ListByCategory", "Home")'" />
                            @*show selected products from the above checkbox*@
                            @if (Model.SelectedProducts != null)
                            {
                                for (int i = 0; i < Model.SelectedProducts.Count; i++)
                                {
                                    @Model.SelectedProducts[i]
                                    <br />
                                }
                            }
}

public class Product
    {
        public int ProductId { get; set; }
        public string ProductName { get; set; }
        public bool IsSelected { get; set; }
    }

    public class OnlineShopModel
    {

        public List<Product> Products { get; set; }
        public List<string> SelectedProducts { get; set; }
    }