我正在使用 Linq to SQL 将我的数据库映射到基础对象。我将所有表拖到我的 dbml 中，它们都设置得很好。我保存 dbml 并创建代表表的类等。
在我的数据库中，我有一个这样的表：
CREATE TABLE [dbo].[BidNames](
[BidNameID] [int] IDENTITY(1,1) NOT NULL,
[CustomerID] [int] NOT NULL,
[BidName] [varchar](75) NOT NULL,
CONSTRAINT [PK_BidNames] PRIMARY KEY CLUSTERED
(
[BidNameID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]
BidNameID 字段显然是一个主键，显然不是 NULL。然而，Linq 像这样定义 BidNameID：
[global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_BidNameID", DbType="Int")]
public System.Nullable<int> BidNameID
{
get
{
return this._BidNameID;
}
set
{
if ((this._BidNameID != value))
{
if (this._BidName1.HasLoadedOrAssignedValue)
{
throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException();
}
this.OnBidNameIDChanging(value);
this.SendPropertyChanging();
this._BidNameID = value;
this.SendPropertyChanged("BidNameID");
this.OnBidNameIDChanged();
}
}
}
其中 BidNameID 定义为 System.Nullable。我数据库中的所有其他表都正确解析，所以我想知道为什么会这样。有任何想法吗？
提前致谢。
编辑
我发现这个问题与另一个表有关。如果我从我的 dbml 中删除 Bids 表并重新保存，BidNameID 列会正确解析为 int。如果我把 Bids 表放回去并保存它会返回 Nullable。Bids 表在 BidNames 表中有一个外键，但数据是干净的。这是投标表的结构：
CREATE TABLE [dbo].[Bids](
[BidID] [int] IDENTITY(1,1) NOT NULL,
[CustomerID] [int] NOT NULL,
[ItemID] [int] NOT NULL,
[Amount] [money] NOT NULL,
[BidName] [varchar](75) NOT NULL,
[BidTime] [datetime] NOT NULL,
[BidNameID] [int] NULL,
CONSTRAINT [PK_Bids] PRIMARY KEY CLUSTERED
(
[BidID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]
ALTER TABLE [dbo].[Bids] WITH CHECK ADD CONSTRAINT [FK_Bids_BidNames] FOREIGN KEY([BidNameID])
REFERENCES [dbo].[BidNames] ([BidNameID])
GO
ALTER TABLE [dbo].[Bids] CHECK CONSTRAINT [FK_Bids_BidNames]
GO
ALTER TABLE [dbo].[Bids] WITH CHECK ADD CONSTRAINT [FK_Bids_Customers] FOREIGN KEY([CustomerID])
REFERENCES [dbo].[Customers] ([CustomerID])
GO
ALTER TABLE [dbo].[Bids] CHECK CONSTRAINT [FK_Bids_Customers]
GO
ALTER TABLE [dbo].[Bids] WITH CHECK ADD CONSTRAINT [FK_Bids_Items] FOREIGN KEY([ItemID])
REFERENCES [dbo].[Items] ([ItemID])
GO
ALTER TABLE [dbo].[Bids] CHECK CONSTRAINT [FK_Bids_Items]
GO