Linq making primary key system.nullable<int> not just int - linq

Question

I'm mapping my database into base object with Linq to SQL. I drag all the tables into my dbml and they all setup nicely. I save the dbml and it creates the classes that represent the tables, etc.
In my database I have a table as such:
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]
The BidNameID field is clearly a primary key and obviously NOT NULL. Linq, however defines BidNameID like this:
[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();
}
}
}
Where BidNameID is defined as System.Nullable. All the other tables in my database resolve correctly so I'm left wondering why this is happening. Any ideas?
Thanks in advance.
EDIT
I have discovered that this problem is related to another table. If I drop the Bids table from my dbml and re-save, the BidNameID column correctly resolves to int. If I put the Bids table back and save it goes back to Nullable. The Bids table has a foreign key into the BidNames table but the data is clean. Here is the structure of the Bids table:
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

Answer 1

I took your table script, ran in my DB and dragged it into a dbml and it didn't generate as nullable (VS2010, VB.NET 4.0):
<Global.System.Data.Linq.Mapping.ColumnAttribute(
Storage:="_BidNameID", AutoSync:=AutoSync.OnInsert,
DbType:="Int NOT NULL IDENTITY", IsPrimaryKey:=True,
IsDbGenerated:=True)>
Public Property BidNameID() As Integer
Get
Return Me._BidNameID
End Get
Set(value As Integer)
If ((Me._BidNameID = value) _
= False) Then
Me.OnBidNameIDChanging(value)
Me.SendPropertyChanging()
Me._BidNameID = value
Me.SendPropertyChanged("BidNameID")
Me.OnBidNameIDChanged()
End If
End Set
End Property
Maybe try one or more of these?
drop/recreate the physical table
delete/recreate your DB connection in Server Explorer
delete/recreate the dbml
manually edit the designer file
create additional datacontext partial class and manually maintain that table/mapping

Answer 2

I don't necessarily understand why but when I alter the Bids table and make the BidNameID field NOT NULL, it fixes the problem with the BidName.BidNameID field. It now resolves to int rather than nullable.