陣列我想爲我的網站創建購物車的界限之外，我有這個下面我的購物車控制線：指數在MVC
public ActionResult AddToCart(int id)
{
repository = new Repository();
// Retrieve the album from the database
var addedProduct = repository.FindProductByIdSingle(id);
// Add it to the shopping cart
var cart = ShoppingCart.GetCart(this.HttpContext);
cart.AddToCart(addedProduct);
// Go back to the main store page for more shopping
return RedirectToAction("Index","Home");
}
這下面類我的購物車模型模型文件夾：
Cart.cs
public class Cart
{
public int RecordId { get; set; }
public string CartId { get; set; }
public int ProductId { get; set; }
public int Count { get; set; }
public System.DateTime DateCreated { get; set; }
public virtual Product Product { get; set; }
}
Order.cs
public class Order
{
public int OrderId { get; set; }
public string Name { get; set; }
public string Address { get; set; }
public string State { get; set; }
public string Phone { get; set; }
public string Email { get; set; }
public decimal Total { get; set; }
public System.DateTime OrderDate { get; set; }
public List<OrderDetail> OrderDetails { get; set; }
}
OrderDetails.cs
public class OrderDetail
{
public int OrderDetailId { get; set; }
public int OrderId { get; set; }
public int ProductId { get; set; }
public int Quantity { get; set; }
public decimal UnitPrice { get; set; }
public virtual Product product { get; set; }
public virtual Order Order { get; set; }
}
ProductEntities.cs
public class ProductEntities: DbContext
{
public DbSet<Product> Products { get; set; }
public DbSet<Cart> Carts { get; set; }
public DbSet<Order> Orders { get; set; }
public DbSet<OrderDetail> OrderDetails { get; set; }
}
ShoppingCart.cs
public class ShoppingCart
{
ProductEntities storeDB = new ProductEntities();
string ShoppingCartId { get; set; }
public const string CartSessionKey = "CartId";
public static ShoppingCart GetCart(HttpContextBase context)
{
var cart = new ShoppingCart();
cart.ShoppingCartId = cart.GetCartId(context);
return cart;
}
// Helper method to simplify shopping cart calls
public static ShoppingCart GetCart(Controller controller)
{
return GetCart(controller.HttpContext);
}
public void AddToCart(Product product)
{
// Get the matching cart and album instances
var cartItem = storeDB.Carts.SingleOrDefault(
c => c.CartId == ShoppingCartId
&& c.ProductId == product.Id);
if (cartItem == null)
{
// Create a new cart item if no cart item exists
cartItem = new Cart
{
ProductId = product.Id,
CartId = ShoppingCartId,
Count = 1,
DateCreated = DateTime.Now,
Product = product
};
storeDB = new ProductEntities();
storeDB.Carts.Add(cartItem);// Error Error
}
else
{
// If the item does exist in the cart,
// then add one to the quantity
cartItem.Count++;
}
// Save changes
storeDB.SaveChanges();
}
}
當我運行項目爲第一次在我的購物類下面的行拋出此異常：
storeDB.Carts.Add（cartItem）; //錯誤錯誤
未將對象引用設置爲對象的實例。
但有些時候拋出這個異常：
指數越界陣列
和我的堆棧跟蹤這下面一行：
[的NullReferenceException：對象引用未設置爲對象的實例。] System.Data.Entity.Core.Metadata.Edm.MetadataOptimization。 GetCSpaceAssociationType（AssociationType osAssociationType）38 System.Data.Entity.Core.Objects.DataClasses.RelatedEnd.FindRelationshipSet（ObjectContext的上下文中，EntitySet的EntitySet的，EdmType &關係類型，RelationshipSet & relationshipSet）202個 System.Data.Entity.Core.Objects .DataClasses.RelatedEnd.AttachContext（ObjectContext上下文，EntitySet entitySet，MergeOption mergeOption）+312 System.Data.Entity.Core.Objects.DataClasses.RelatedEnd.AttachContext（ObjectContext上下文，MergeOption mergeOption）+178 System.Data.Entity。 Core.Objects.DataClasses.RelationshipManager.CreateRelatedEnd（RelationshipNavigation navigation，RelationshipMultiplicity sourceRoleMultiplicity，RelationshipMultiplicity targetRoleMultiplicity，RelatedEnd existingRelatedEnd）+627 System。 Data.Entity.Core.Objects.DataClasses.RelationshipFixer
2.System.Data.Entity.Core.Objects.DataClasses.IRelationshipFixer.CreateSourceEnd(RelationshipNavigation navigation, RelationshipManager relationshipManager) +116 System.Data.Entity.Core.Objects.DataClasses.RelationshipManager.GetRelatedEnd(RelationshipNavigation navigation, IRelationshipFixer relationshipFixer) +129 System.Data.Entity.Core.Objects.DataClasses.RelatedEnd.GetOtherEndOfRelationship(IEntityWrapper wrappedEntity) +93 System.Data.Entity.Core.Objects.DataClasses.RelatedEnd.IncludeEntity(IEntityWrapper wrappedEntity, Boolean addRelationshipAsUnchanged, Boolean doAttach) +231 System.Data.Entity.Core.Objects.DataClasses.EntityReference1.Include（布爾addRelationshipAsUnchanged，布爾doAttach）+210 System.Data.Entity.Core.Objects.DataClasses.RelationshipManager.AddRelatedEntitiesToObjectStateManager（布爾doAttach）+164 System.Data .Entity.Core.Objects.ObjectContext.AddObject（String entitySetName，Object entity）+521 System.Data.Entity.Internal.Linq。 <> c__DisplayClassd.b__c（）+98 System.Data.Entity.Internal.Linq.InternalSet1.ActOnSet(Action action, EntityState newState, Object entity, String methodName) +355 System.Data.Entity.Internal.Linq.InternalSet1。添加（對象實體）200個 System.Data.Entity.DbSet1.Add(TEntity entity) +131 MobileShop.Models.ShoppingCart.AddToCart(Product product) in d:\Projects\Asp.net\MobileShop\MobileShop\Models\ShoppingCart.cs:46 MobileShop.Controllers.ShoppingCartController.AddToCart(Int32 id) in d:\Projects\Asp.net\MobileShop\MobileShop\Controllers\ShoppingCartController.cs:40 lambda_method(Closure , ControllerBase , Object[]) +161 System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +59 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2參數）434 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod（ControllerContext controllerContext，ActionDescriptor actionDescriptor，IDictionary的2 parameters) +60 System.Web.Mvc.Async.ActionInvocation.InvokeSynchronousActionMethod() +76 System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) +36 System.Web.Mvc.Async.WrappedAsyncResult2.CallEndDelegate（IAsyncResult的asyncResult）73 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +136 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +102 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +49 System.Web.Mvc.Async.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d() +117 System.Web.Mvc.Async.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() +323 System.Web.Mvc.Async.<>c__DisplayClass33.<BeginInvokeActionMethodWithFilters>b__32(IAsyncResult asyncResult) +44 System.Web.Mvc.Async.WrappedAsyncResult1.CallEndDelegate（IAsyncResult的asyncResult）47 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +136 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +102 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +50 System.Web.Mvc.Async.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() +72 System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) +185 System.Web.Mvc.Async.WrappedAsyncResult1.CallEndDelegate（IAsyncResult的asyncResult）42 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +133 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +40 System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +34 System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate（IAsyncResult asyncResult）+70 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +139 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40 System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +44 System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) +39 System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate（IAsyncResult asyncResult）+62 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +139 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40 System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +39 System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +39 System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +39 System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate（IAsyncResult的asyncResult）70 System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）139 System.Web.Mvc.Async.AsyncResultWrapper.End （IAsyncResult asyncResult，Object tag）+59 System.Web.Mvc.Async.AsyncResultWrapper.End（IAsyncResult asyncResult，Object tag）+40 System.Web.Mvc.MvcHandler.EndProcessRequest（IAsyncResult asyncResult）+40 System.Web .Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest（IAsyncResult result）+38 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute（）+9690172 System.Web.HttpApplication.ExecuteStep（IExecutionStep步驟，布爾& completedSynchro ）+155
注意：當我向cartItem添加新購物車時，產品有factorDetail fielde，它是空的，所以它有關係嗎？
注2：我使用本教程Part 8: Shopping Cart with Ajax Updates | The ASP.NET Site
因此，如何我解決了這個例外？
這些'storeDB.Carts.Add（cartItem）'調試器中的哪一個告訴你爲空？ 'storeDB'，'Carts'或者'cartItem'？ – Jasen
目前尚不清楚 –