關於Delphi的一個查詢From的編程

如題,剛入行Delphi不太久. 努力了1天.寫出如下代碼:

unit Projectfrm;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls, Grids, DBGrids, DB, ADODB, ComCtrls, StdCtrls;

type
  TProjectForm = class(TForm)
    lblDate: TLabel;
    lblStage: TLabel;
    cbStage: TComboBox;
    dtpSta: TDateTimePicker;
    dtpOver: TDateTimePicker;
    lbl: TLabel;
    dsStageDetail: TDataSource;
    DBConn: TADOConnection;
    qryStage: TADOQuery;
    dbGirdStage: TDBGrid;
    btnYes: TButton;
    procedure btnYesClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  ProjectForm: TProjectForm;

implementation

{$R *.dfm}

procedure TProjectForm.btnYesClick(Sender: TObject);
begin
  if StrToInt(cbStage.Text) in [010,020,030,110] then
  begin
    qryStage.Close;
    qryStage.SQL.Clear;
    qryStage.SQL.Add('select * from DStageDetail where Stage='''+cbStage.Text+'''');
    qryStage.SQL.Add(' and outputdate >= '+formatdatetime('yyyymmdd',dtpSta.Date) );
    qryStage.SQL.Add(' and ProdDate <= '+formatdatetime('yyyymmdd',dtpOver.Date) );
    qryStage.Open;
  end
  else
  begin
    qryStage.Close;
    qryStage.SQL.Clear;
    qryStage.SQL.Add('select * from DFQCDetail where Stage='''+cbStage.Text+'''');
    qryStage.SQL.Add(' and outputdate >= '+formatdatetime('yyyymmdd',dtpSta.Date) );
    qryStage.SQL.Add(' and outputdate <= '+formatdatetime('yyyymmdd',dtpOver.Date) );
    qryStage.Open;
  end;
end

------我是分割線------

具體我真的不太知道錯誤在哪里.因為我按照.net里面if-else的理論來看,沒問題應該是,cbStage是一個下拉框.
我有試過用: cbStage.Items.text in [...] 可是結果一樣運行不出來.我覺得應該是格式問題,代碼或許有點小問題,求
好心人指點.不然我要被老板罵一死. 剛學,不懂還望老鳥多多指教