无法附加以存在的实体
private void Form1_Load(object sender, EventArgs e)
  {
  bool b = false;
  Table<a> ldt;
  ldt = Selectall(); 
  foreach (a t in ldt)
  {
  t.c = "asdf";
   
  b =Updater(a2);
  if (b)
  {
  MessageBox.Show("修改成功 ！");
  }
  else
  {
  MessageBox.Show("修改失败！");
  }
  }
  }
  public Table<a> Selectall()
  {
  try
  {
  return ddc.a;
  }
  catch (Exception ee)
  {
  throw ee;
  }
  }
  public bool Updater(a ts)
  {
  try
  {
  ddc.a.Attach(ts);
  ddc.Refresh(RefreshMode.KeepCurrentValues, ts);
  ddc.SubmitChanges(ConflictMode.ContinueOnConflict);
  return true;
  }
  catch(Exception e)
  {
  MessageBox.Show(e.Message);
  return false;
  }
  }
运行后总提示修改不成功，无法附加以存在的实体。这是哪里错了？

------解决方案--------------------
a a1;//实体
a1 = SelectSingle(); //假设查询返回实体而非实体集 
a a2=new a();
a2.title =a1.title();
a2.content = "我爸李刚";

linqDataContext ddc=new LinqDateDataContext();
ddc.admin.Attach(a2);
ddc.Refresh(RefreshMode.KeepCurrentValues, a2);
ddc.SubmitChanges(ConflictMode.ContinueOnConflict);
------解决方案--------------------

探讨

a a1;//实体
a1 = SelectSingle(); //假设查询返回实体而非实体集
a a2=new a();
a2.title =a1.title();
a2.content = "我爸李刚";

linqDataContext ddc=new LinqDateDataContext();
ddc.admin.Attach(a2);
ddc.Refresh(Refr……