▲▲▲这段C++Builder代码输入正确的用户名密码能正常登陆,输入错误的用户名密码提示时提示BOF或EOF中有一个是真,怎么回事,怎么改▲▲▲

Question

void __fastcall TForm1::Button1Click(TObject *Sender)
    {
      try
      {
        int  passcount; // passcount是整数？
        AnsiString sql;
        sql="select * from users where u_name='"
        +Edi_user->Text
        +"'and u_passwd='"
        +Edi_pass->Text
        +"'";        ADOQuery1->SQL->Add(sql);
        ADOQuery1->Close();
        ADOQuery1->Open();
        if(ADOQuery1->RecordCount==1)
        {
          Frm_Login->Hide();
          TFrm_Main=new TFrm_Main(Application);
          Frm_Main->ShowModal();
        }
        else if(passcount<=2)    // passcount是整数？
        {
          passcount++;
          Application->MessageBox("密码输入错误，请重新输入！","错误",MB_ICONWARNING);
          passcount++;
          Edi_pass->Text="";
          Edi_pass->SetFocus();
        }
        else
        {
          Application->Terminate();
        }
      }
      catch(...)
      {
        return;
      }
    }

Answer 1

ADOQuery1->SQL->Add(sql);
        ADOQuery1->Close();
        ADOQuery1->Open();
--------------
這里面SQL->Add和Close的位置要換一下
        ADOQuery1->Close();
        ADOQuery1->SQL->Add(sql);
        ADOQuery1->Open();要判斷RecordCount之前先確實是否ADOQuery當中有數據,即判斷是否Eof()和Bof為True.