linq 修改提交给事物拦截后再次提交不更新数据库

 bool bo = false;
        private void simpleButton1_Click(object sender, EventArgs e)
        {
            using (System.Transactions.TransactionScope scope = new System.Transactions.TransactionScope())
            {
                try
                {
                    CoreProject.Service.EmployeeService.GetSObj.aa(userState.Employee, bo);
                    
                   
                    scope.Complete();//提交事务                  
                }
                catch (Exception ee)
                {
                    bo = true;                  
                    this.ShowMessageBox(ee.Message);
                }
                finally
                {
                    scope.Dispose();//回滚事务
                }
            }
        }

//-----------在EmployeeService类中的方法

public void UpdateName(Employee employee, bool bo)
        {
            var obj = (from d in db.DEF_Employee where d.Id == employee.Id select d).SingleOrDefault();
            if (obj == null)
                return;

            obj.Name = "aaaa";
            db.SubmitChanges()
            if (!bo)
            {
                //db = new DataDBDDataContext(ConStr); 
 
                throw new Exception("第一次提交失败");
            }
        }

第二次提交时未执行代码obj.Name = "aaaa";之前 obj.Name已经在第一次提交时改为"aaaa"
我尝试过将db = new DataDBDDataContext(ConStr);重新实例后第二次提交任然失败

DEF_Employee 类有设置主键
[global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_Id", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
public int Id
{
get
{
return this._Id;
}
set
{
if ((this._Id != value))
{
this.OnIdChanging(value);
this.SendPropertyChanging();
this._Id = value;
this.SendPropertyChanged("Id");
this.OnIdChanged();
}
}
}

[最优解释]
Try:
obj.Name = "aaaa";

db.SubmitChanges(ConflictMode.FailOnFirstConflict);
// or
db.SubmitChanges(ConflictMode.ContinueOnConflict);

[其他解释]
CoreProject.Service.EmployeeService.GetSObj.aa(userState.Employee, bo);
方法名称aa写错 对应方法是UpdateName
[其他解释]

public void UpdateName(Employee employee, bool bo)
        {
            var obj = (from d in db.DEF_Employee where d.Id == employee.Id select d).SingleOrDefault();
            if (obj == null)
                return;

            db.Refresh(System.Data.Linq.RefreshMode.OverwriteCurrentValues, obj);
            db.SubmitChanges();


            obj.Name = "aaaa";
            db.SubmitChanges()
            if (!bo)
            {
                                //db = new DataDBDDataContext(ConStr);
                throw new Exception("第一次提交失败");
            }
        }

这样就解决了,但是性能估计下降很多。