Question

delphi dm.ADOQuery1:missing SQL property

我做的是个登陆框
请达人指点那里有问题
interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm2 = class(TForm)
GroupBox1: TGroupBox;
RadioButton1: TRadioButton;
RadioButton2: TRadioButton;
GroupBox2: TGroupBox;
Label1: TLabel;
Label2: TLabel;
Edit1: TEdit;
Edit2: TEdit;
Button1: TButton;
Button2: TButton;

procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form2: TForm2;
m:integer;
czy:string;
s:boolean;
implementation
uses
Unit1;
{$R *.dfm}

procedure TForm2.Button2Click(Sender: TObject);
begin
close;
end;

procedure TForm2.Button1Click(Sender: TObject);
begin

m:=m+1;

if edit1.Text='' then

begin
dm.ADOQuery1.close;
dm.ADOQuery1.open;
application.MessageBox('请输入用户名','提示',64);

end
else

if edit2.Text='' then
begin
dm.ADOQuery1.close;
dm.ADOQuery1.open;
application.MessageBox('请输入密码','提示',64) ;

end
else

begin

dm.ADOQuery1.Close;

dm.ADOQuery1.SQL.Clear;

dm.ADOQuery1.sql.Add('select * from cuser where username = :a and pass = :b');

dm.ADOQuery1.parameters.ParamByName('a').Value:=trim(edit1.Text);

dm.ADOQuery1.parameters.ParamByName('b').Value:=trim(edit2.Text);

dm.ADOQuery1.open;

end;

if dm.ADOQuery1.RecordCount>0 then
begin

czy:=dm.ADOQuery1.FieldByName('username').Value;

s:=true;

form2.Hide;

end

else

if m<3 then

begin

application.MessageBox('用户名或密码错误，请重新输入！','提示',64);

edit1.Clear;

edit2.Clear;

edit1.SetFocus;

end

else
begin

application.MessageBox('您无权使用本系统！','提示',64);

Application.Terminate;

end;

end;

end.

Answer 1

记住：在ADOquery.open前一定确保它的SQL中有语句。就是这个原因。
Button1的Click事件中有几处明显就是这个原因了。

Answer 2

dm.ADOQuery1.close;
dm.ADOQuery1.open;

有两处这个去掉试下，因为提示的信息显示ADOQuery1的SQL属性未设置，大概只有这个地方可以引起这个问题了