使用LINQ to SQL进行更新的最有效方法

Question

我可以更新下面函数中给出的员工记录,还是先查询员工集合,然后更新数据？

  public int updateEmployee(App3_EMPLOYEE employee)
  {
      DBContextDataContext db = new DBContextDataContext();
      db.App3_EMPLOYEEs.Attach(employee);
      db.SubmitChanges();
      return employee.PKEY;
  }

或者我必须做以下事情？

public int updateEmployee(App3_EMPLOYEE employee)
{
    DBContextDataContext db = new DBContextDataContext();
    App3_EMPLOYEE emp = db.App3_EMPLOYEEs.Single(e => e.PKEY == employee.PKEY);
    db.App3_EMPLOYEEs.Attach(employee,emp);
    db.SubmitChanges();
    return employee.PKEY;
}

但我不想使用第二种选择.有没有有效的方法来更新数据？

我通过两种方式得到此错误:

已尝试附加或添加非新的实体,可能已从另一个DataContext加载.这不受支持.

Answer 1

我找到了以下解决此问题的方法:

1)获取和更新实体(我将使用这种方式,因为它对我来说没问题)

public int updateEmployee(App3_EMPLOYEE employee)
{
    AppEmployeeDataContext db = new AppEmployeeDataContext();
    App3_EMPLOYEE emp = db.App3_EMPLOYEEs.Single(e => e.PKEY == employee.PKEY);
    emp.FIRSTNAME = employee.FIRSTNAME;//copy property one by one 
    db.SubmitChanges();
    return employee.PKEY;
}

2)禁用ObjectTrackingEnabled如下

// but in this case lazy loading is not supported


    public AppEmployeeDataContext() : 
                    base(global::LinqLibrary.Properties.Settings.Default.AppConnect3DBConnectionString, mappingSource)
            {
                this.ObjectTrackingEnabled = false;
                OnCreated();
            }

3)分离所有相关对象

partial class App3_EMPLOYEE
{
    public void Detach()
    {
        this._APP3_EMPLOYEE_EXTs = default(EntityRef<APP3_EMPLOYEE_EXT>);
    }
}

 public int updateEmployee(App3_EMPLOYEE employee)
{
    AppEmployeeDataContext db = new AppEmployeeDataContext();
    employee.Detach();
    db.App3_EMPLOYEEs.Attach(employee,true);
    db.SubmitChanges();
    return employee.PKEY;
}

4)在列中使用时间戳

 http://www.west-wind.com/weblog/posts/135659.aspx

5)创建用于更新数据的存储过程,并通过db context调用它