My Shopping Cart is not working as expected in ASP.NET MVC 5 - asp.net-mvc-5

Question

My cart is working fine in localhost but when i have hosted in cloud hosting it is not working well problem is that when i click add to cart button it will add one product with one quantity but when i add another product in the cart again it will override the previous one and show only one product in cart when i have added on last.. i don't know whats wrong with the sessions it will override the session again i guess. And another problem is that my my update cart button's functionalities and delete button functionalities in cart is not working it throw exception
Object reference not set to an instance of an object.
I have a controller name shoppingCartController here is the code
namespace Medi.Areas.User.Controllers
{
public class ShoppingCartController : Controller
{
ArrayList arr = new ArrayList();
int id;
BLL.IRepository<tbl_Product> de = new BLL.IRepository<tbl_Product>();
public ActionResult Index()
{
return View();
}
private int isExisting(int id)
{
List<Items> cart = (List<Items>)Session["cart"];
for (int i = 0; i < cart.Count; i++)
if (cart[i].Pr.ProductID == id)
return i;
return -1;
}
public ActionResult Delete(int id)
{
int index = isExisting(id);
List<Items> cart = (List<Items>)Session["cart"];
cart.RemoveAt(index);
Session["cart"] = cart;
return PartialView("_pvCart");
}
public ActionResult OrderNow(string q)
{
if (Session["cart"] == null)
{
List<Items> cart = new List<Items>();
cart.Add(new Items(de.GetById(Convert.ToInt32(q)), 1));
Session["cart"] = cart;
// ViewBag.quantity = new MultiSelectList(cart,"Quantity","Quantity");
// cart[1]
}
else
{
id = Convert.ToInt32(q);
List<Items> cart = (List<Items>)Session["cart"];
int index = isExisting(id);
if (index == -1)
cart.Add(new Items(de.GetById(id), 1));
else
cart[index].Quantity++;
Session["cart"] = cart;
// ViewBag.quantity = new MultiSelectList(cart, "Quantity", "Quantity");
}
return View("Cart");
}
[HttpPost]
public ActionResult UpdateCart(int[] ProductID,int [] quantity )
{
int[] x = new int[4];
int[] y = new int[4];
List<Items> cart = (List<Items>)Session["cart"];
for (int i = 0; i < cart.Count; i++)
{
x[i] = ProductID[i];
y[i] = quantity[i];
updcart(x[i],y[i]);
}
Session["cart"] = cart;
return PartialView("_pvCart");
}
public void updcart(int id,int quantity) {
List<Items> cart = (List<Items>)Session["cart"];
int index = isExisting(id);
if (index == -1)
cart.Add(new Items(de.GetById(id), 1));
else
cart[index].Quantity = quantity;
Session["cart"] = cart;
}
}
}
and here is the view name Cart.cshtml
#{
ViewBag.Title = "Cart";
Layout = "~/Views/Shared/_Layout.cshtml";
}
<script src="~/Scripts/jquery-2.1.4.js"></script>
<script src="~/Scripts/jquery.unobtrusive-ajax.js"></script>
#using (Ajax.BeginForm("UpdateCart", "ShoppingCart", new AjaxOptions() { HttpMethod = "POST", UpdateTargetId = "MyData", InsertionMode = InsertionMode.Replace }))
{
#Html.AntiForgeryToken()
<br />
<br />
<div id="MyData">
#{Html.RenderPartial("_pvCart");}
and here is the partial view code
#using Medi.Models;
<script src="~/Scripts/metro.min.js"></script>
<table class="table hovered" cellpadding=" 2" cellspacing="2" border="1px">
<tr class="info">
<th></th>
<th>Name</th>
<th>Price</th>
<th>Quantity</th>
<th>Sub Total</th>
</tr>
#{
decimal s = 0;
}
#foreach (Items item in (List<Items>)Session["cart"])
{
<input id="ProductID" name="ProductID" type="hidden" value="#item.Pr.ProductID" />
s = s + (Convert.ToInt32(item.Pr.Price) * item.Quantity);
<tr>
<th>#Ajax.ActionLink("Delete", "Delete", new { id = item.Pr.ProductID }, new AjaxOptions() { HttpMethod = "POST", UpdateTargetId = "MyData", InsertionMode = InsertionMode.Replace }, new { #class = "mif-cross" })</th>
<td>#item.Pr.ProductName</td>
<td>#item.Pr.Price</td>
<td>
<input name="quantity" id="quantity" type="text" style="width:25px;" value="#item.Quantity" />
</td>
<td>#(item.Pr.Price * item.Quantity)</td>
</tr>
}
</table><br />
<hr />
<table cellpadding="1px" cellspacing="1px" style="float:right;">
<tr align="center" colspan="5" style="background-color:gray;">
<td><h3 style="padding:1px;">Total</h3></td>
<td> <h3 style="padding:1px;">Rs #s</h3></td>
</tr>
</table>
here is the model class
using BOL;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace Medi.Models
{
public class Items
{
tbl_Product pr = new tbl_Product();
public tbl_Product Pr
{
get { return pr; }
set { pr = value; }
}
int quantity;
public int Quantity { get; set; }
public Items()
{
}
public Items(tbl_Product product, int quantity)
{
this.Pr = product;
this.Quantity = quantity;
}
}
}
i have also write this code in web.config
<httpCookies httpOnlyCookies="true" requireSSL="true"/>
<sessionState mode="InProc"/>