当从左到右滚动数据网格视图时，Object dispose异常

我使用Linq到SQL类来管理数据，并使用以下代码将数据绑定到Windows窗体中的dataGridview。当我试图从左向右滚动datagdview时抛出异常。

这里涉及的两个表是:

billing_UserRole

RoleId PK

RoleName

CreatedTS

UpdatedTS

billing_User

UserId PK//在其他一些表中也被引用。

RoleId颗

用户名

密码

FirstName

LastName

CreatedTS

UpdatedTS

创建表的查询遵循

CREATE TABLE [dbo].[billing_UserRole](
bk_UserRoleId BIGINT IDENTITY(100,1) NOT NULL,
bk_UserRoleName NVARCHAR(128) NOT NULL,
bk_CreatedTS DATETIME NULL,
bk_UpdatedTS DATETIME NULL,
CONSTRAINT [PK_billingUserRole] PRIMARY KEY CLUSTERED
(
    [bk_UserRoleId] ASC 
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

/* TABLE NAME : billing_User */
CREATE TABLE [dbo].[billing_User](
    bk_UserId BIGINT IDENTITY(1,1) NOT NULL,
    bk_Username NVARCHAR(256) NOT NULL,
    bk_Password NVARCHAR(2048) NOT NULL DEFAULT('none'),
    bk_FirstName NVARCHAR(256) NOT NULL,
    bk_LastName NVARCHAR(256) NOT NULL,
    bk_MobileNo NVARCHAR(128) NOT NULL,
    bk_Address NVARCHAR(2048) NULL DEFAULT('none'),
    bk_Remarks NVARCHAR(2048) NULL DEFAULT('none'),
    bk_UserRoleId BIGINT NOT NULL,
    bk_CreatedTS DATETIME NULL,
    bk_UpdatedTS DATETIME NULL,
CONSTRAINT [PK_billingUser] PRIMARY KEY CLUSTERED 
(
    [bk_UserId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY],
CONSTRAINT [FK_billingUser_billingUserRole] FOREIGN KEY(bk_UserRoleId) REFERENCES [dbo].[billing_UserRole](bk_UserRoleId)
) 

form中绑定datagridview到form_load

 private void UserManagementForm_Load(object sender, EventArgs e)
        {
            try
            {
                using (BillingKioskDataLayerDataContext dc = new BillingKioskDataLayerDataContext())
                {
                    Table<billing_User> UserTable = dc.GetTable<billing_User>();
                    var UserList = UserTable.Select(o=>o).ToList();
                    billing_UserBindingSource.DataSource = UserList;
                    dataGridView1.DataSource = billing_UserBindingSource;

                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex.Message);   
            }
        }

下面是抛出异常的代码。这是一个自动生成的代码。为什么会这样呢?当我滚动DataGridView从左到右查看剩余字段时，我只得到这个异常。

[global::System.Data.Linq.Mapping.AssociationAttribute(Name="billing_UserRole_billing_User", Storage="_billing_UserRole", ThisKey="bk_UserRoleId", OtherKey="bk_UserRoleId", IsForeignKey=true)]
            public billing_UserRole billing_UserRole
            {
                get
                {
                    return this._billing_UserRole.Entity; **// I get DisposedObjectException :Cannot access a disposed object here**
                }
                set
                {
                    billing_UserRole previousValue = this._billing_UserRole.Entity;
                    if (((previousValue != value) 
                                || (this._billing_UserRole.HasLoadedOrAssignedValue == false)))
                    {
                        this.SendPropertyChanging();
                        if ((previousValue != null))
                        {
                            this._billing_UserRole.Entity = null;
                            previousValue.billing_Users.Remove(this);
                        }
                        this._billing_UserRole.Entity = value;
                        if ((value != null))
                        {
                            value.billing_Users.Add(this);
                            this._bk_UserRoleId = value.bk_UserRoleId;
                        }
                        else
                        {
                            this._bk_UserRoleId = default(long);
                        }
                        this.SendPropertyChanged("billing_UserRole");
                    }
                }
            }

堆栈跟踪:

 at System.Data.Linq.DataContext.GetTable(Type type)
   at System.Data.Linq.CommonDataServices.GetDataMemberQuery(MetaDataMember member, Expression[] keyValues)
   at System.Data.Linq.CommonDataServices.DeferredSourceFactory`1.ExecuteKeyQuery(Object[] keyValues)
   at System.Data.Linq.CommonDataServices.DeferredSourceFactory`1.Execute(Object instance)
   at System.Data.Linq.CommonDataServices.DeferredSourceFactory`1.DeferredSource.GetEnumerator()
   at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
   at System.Data.Linq.EntityRef`1.get_Entity()
   at BillingKiosk.billing_User.get_billing_UserRole() in e:'XGHProjects'BillingKiosk'BillingKiosk'BillingKioskDataLayer.designer.cs:line 663