同样的方法在FormCreate事件中正常执行但在OnClick事件中就不能正常执行(0分)

unit Unit1


interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, Grids, DBGrids, FlatCustomControl, FlatPanel, FlatSystem, DataHandle,
TB2Item, TB2Dock, TB2Toolbar, ToolWin, ComCtrls, StdCtrls


type
TForm1 = class(TForm)
FlatSystem1: TFlatSystem

FlatPanel1: TFlatPanel

DBGrid1: TDBGrid

Button1: TButton

procedure Button1Click(Sender: TObject)

procedure FormCreate(Sender: TObject)

private
{ Private declarations }
public
{ Public declarations }
end


var
Form1: TForm1


implementation

{$R *.dfm}



procedure TForm1.Button1Click(Sender: TObject)
//此处DBGrid1就无法正常显示
var
dmDataManage : TdmDataManage

begin
Button1.Caption:='dd'

dmDataManage:=TdmDataManage.Create(Application)

dmDataManage.SetSQL('select * from worker')

DBGrid1.Refresh

end


procedure TForm1.FormCreate(Sender: TObject)
//此处正常

var
dmDataManage : TdmDataManage

begin
Button1.Caption:='dd'

dmDataManage:=TdmDataManage.Create(Application)

dmDataManage.SetSQL('select * from worker')

DBGrid1.Refresh

end


end.

TdmDataManage是一个数据模块，里面有一个ADOQuery和一个DataSouce ，
错误情况是在Onclick中的DBGrid1不进行刷新。但能编译通过，执行时程序也不报导错。

是不是那段代码不能重复执行