c# - 不能将重复值插入到唯一索引中(但是...)

Question

我正在尝试将产品添加到购物车，但它返回以下内容:

更新条目时发生错误。有关详细信息，请参阅内部异常。

Inner exception: System.Data.SqlServerCe.SqlCeException (0x80004005): A duplicate value cannot be inserted into a unique index. [ Table name = Cart,Constraint name = PK_Cart_0000000000000997 ] at System.Data.SqlServerCe.SqlCeCommand.ProcessResults(Int32 hr) at System.Data.SqlServerCe.SqlCeCommand.ExecuteCommandText(IntPtr& pCursor, Boolean& isBaseTableCursor) at System.Data.SqlServerCe.SqlCeCommand.ExecuteCommand(CommandBehavior behavior, String method, ResultSetOptions options) at System.Data.SqlServerCe.SqlCeCommand.ExecuteNonQuery() at System.Data.SqlServerCe.SqlCeMultiCommand.ExecuteNonQuery() at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.Execute(UpdateTranslator translator, EntityConnection connection, Dictionary2
identifierValues, List1 generatedValues) at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter)

Stack trace at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter) at System.Data.EntityClient.EntityAdapter.Update(IEntityStateManager entityCache) at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options) at System.Data.Objects.ObjectContext.SaveChanges() at JTS.Security.Identity.Push.ToCart(Int32 userId, String partNumber, String productDescription, Int32 quantity, Decimal price, Decimal lineTotal, String orderId, DateTime dateTime, Boolean isBoxed) in c:\Users\Jase\Documents\Visual Studio 2012\WebSites\One\App_Code\JTS.cs:line 251

但问题是，我没有任何唯一索引。我什至尝试删除所有主键(只是为了看看这是否会改变任何东西)——但它没有。

代码:

public bool ToCart(int userId,
                    string partNumber,
                    string productDescription,
                    int quantity,
                    decimal price,
                    decimal lineTotal,
                    string orderId,
                    DateTime dateTime,
                    bool isBoxed)
                {
                    bool addedToCart = false;

                    try
                    {
                        Cart cart = new Cart()
                        {
                            UserId = userId,
                            PartNumber = partNumber,
                            Description = productDescription,
                            Quantity = quantity,
                            Price = price,
                            LineTotal = lineTotal,
                            OrderId = orderId,
                            OrderDate = dateTime,
                            IsBoxed = isBoxed
                        };

                        database.AddToCarts(cart);
                        database.SaveChanges();

                        addedToCart = true;
                    }
                    catch (Exception exception)
                    {
                        addedToCart = false;
                        //Response(exception.Message);
                        addToCartExceptionDetails = exception.Message +
                            Environment.NewLine + Environment.NewLine + "Inner exception" +
                            exception.InnerException +
                            Environment.NewLine + Environment.NewLine + "Stack trace" +
                            exception.StackTrace;
                    }

                    return addedToCart;
                }

此外，如果我创建一个新订单(这会创建一个新的 OrderID)，它会向购物车添加一项。但是，它永远不会在现有 OrderId 下向购物车添加超过 1 件商品!

我做错了什么？为什么这不起作用？

表定义

---

Column Name   Data Type   Length   Allow Nulls     Unique    Primary Key
UserId        int         4        Yes             No        No
OrderId       nvarchar    1000     No              No        Yes

Answer 1

如果您有一个表，您在其中删除并重新添加了内容，则在插入 ID 等于现有 ID 的新行时可能会出现此错误你为什么不检查这个Link形成更多信息