Entity Framework Error

[Raad]

I have a little problem. I am encountering the following error each time I try update my entityset.\[quote\] Unable to update the EntitySet 'ShoppingCart' because it has a DefiningQuery and no element exists in the element to support the current operation.\[/quote\]The code is: `\[code\]public void AddItem(string cartID, string productID, string quantity) { using (CommerceEntities db = new CommerceEntities()) { try { var myItem = (from c in db.ShoppingCarts where c.CartID == cartID && c.ProductID == productID select c).FirstOrDefault(); if (myItem == null) { ShoppingCart cartadd = new ShoppingCart(); cartadd.CartID = cartID; cartadd.Quantity = quantity; cartadd.ProductID = productID; cartadd.DateCreated = DateTime.Now; db.ShoppingCarts.AddObject(cartadd); } else { myItem.Quantity += Convert.ToInt32(quantity); } db.SaveChanges(); } catch (Exception exp) { throw new Exception("ERROR: Unable to Add Item to Cart - " +exp.Message); } } }\[/code\]`Please help me. I can provide more information if required, I am new to this Entity Framework Model and following the tutorial on This page.