MVC db.SaveChanges(); 2 Times Error: Object reference not set - asp.net-mvc

Question

I'm getting the error of Object reference not set to an instance of an object. because of the Cart does not exist before it saves the db with the new changes.
I made some notes in my code explaining the problem. And I'm trying to get done
[Authorize]
public ActionResult AddToCart(int productid, string name, string description, decimal price)
{
var userID = User.Identity.GetUserId();
// List of Cart(s) that the current user own.
List<Cart> Carts = db.Carts.Where(x => x.UserId == userID).ToList();
// checks if the list above cotains no cart for the current logged in user.
if (Carts.Find(m => m.UserId == userID) == null) {
Cart cartmodel = new Cart { UserId = userID, CreatedDate = DateTime.Now};
db.Carts.Add(cartmodel);
db.SaveChanges();
}
// this action needs to be delayed til the upper action has been executed because: userCart.Id; has no value yet!
var userCart = Carts.Find(x => x.Id == x.Id);
var MyCartId = userCart.Id;
OrderItem model = new OrderItem { ProductId = productid, Name = name, Description = description, Price = price, CartId = MyCartId, Quantity = 1 };
db.OrderItems.Add(model);
db.SaveChanges();
return RedirectToAction("Cart");
}
Object reference not set
at
var MyCartId = userCart.Id;
The code works if the cart already exists. so after getting the error it does create the Cart for the user but it doesn't do the 2nd action which was to add product to the cart
i attempted to do this but now getting a new error:
[Authorize]
public ActionResult AddToCart(int productid, string name, string description, decimal price)
{
var userID = User.Identity.GetUserId();
// List of Cart(s) that the user owns should allways be 1 only ofc.
List<Cart> Carts = db.Carts.Where(x => x.UserId == userID).ToList();
// checks if the list above cotains no cart for the current logged in user.
if (Carts.Find(m => m.UserId == userID) == null) {
return RedirectToAction("AddNewCart");
}
// this action needs to be delayed til the upper action has been executed becasue: userCart.Id; has no value yet!
// make 2 action results and work with redirect
var userCart = Carts.Find(x => x.Id == x.Id);
var MyCartId = userCart.Id;
OrderItem model = new OrderItem { ProductId = productid, Name = name, Description = description, Price = price, CartId = MyCartId, Quantity = 1 };
db.OrderItems.Add(model);
db.SaveChanges();
return RedirectToAction("Cart");
}
public ActionResult AddNewCart()
{
var userID = User.Identity.GetUserId();
// List of Cart(s) that the user owns should allways be 1 only ofc.
List<Cart> Carts = db.Carts.Where(x => x.UserId == userID).ToList();
Cart cartmodel = new Cart { UserId = userID, CreatedDate = DateTime.Now };
db.Carts.Add(cartmodel);
db.SaveChanges();
return RedirectToAction("AddToCart");
}
the parameters dictionary contains a null entry for parameter 'productid' of non-nullable type 'System.Int32' for method
'System.Web.Mvc.ActionResult AddToCart(Int32, System.String,
System.String, System.Decimal)' in
'BlogMVC.Controllers.WebshopController'. An optional parameter must be
a reference type, a nullable type, or be declared as an optional
parameter.
Parameter name: parameters

Answer 1

I fixed it, but it isnt exacly a clean way of doing it any suggestion to make the code more clean and better would be greatly appciated
[Authorize]
public ActionResult AddToCart(int productid, string name, string description, decimal price)
{
var userID = User.Identity.GetUserId();
// List of Cart(s) that the user owns should allways be 1 only ofc.
List<Cart> Carts = db.Carts.Where(x => x.UserId == userID).ToList();
// checks if the list above cotains no cart for the current logged in user.
if (Carts.Find(m => m.UserId == userID) == null) {
return RedirectToAction("AddNewCart", new { name = name, productid = productid, description = description, price = price });
}
// this action needs to be delayed til the upper action has been executed becasue: userCart.Id; has no value yet!
// make 2 action results and work with redirect
var userCart = Carts.Find(x => x.Id == x.Id);
var MyCartId = userCart.Id;
OrderItem model = new OrderItem { ProductId = productid, Name = name, Description = description, Price = price, CartId = MyCartId, Quantity = 1 };
db.OrderItems.Add(model);
db.SaveChanges();
return RedirectToAction("Cart");
}
public ActionResult AddNewCart(int productid, string name, string description, decimal price)
{
var userID = User.Identity.GetUserId();
// List of Cart(s) that the user owns should allways be 1 only ofc.
List<Cart> Carts = db.Carts.Where(x => x.UserId == userID).ToList();
Cart cartmodel = new Cart { UserId = userID, CreatedDate = DateTime.Now };
db.Carts.Add(cartmodel);
db.SaveChanges();
return RedirectToAction("AddToCart", new { name = name, productid = productid, description = description, price = price });
}