unit2.~pas

基于数据库的登录程序源代码

unit Unit2;

interface

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

type
  TForm2 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Button1: TButton;
    Button2: TButton;
    ADOConnection1: TADOConnection;
    ADOQuery: TADOQuery;
    ComboBox1: TComboBox;
    Edit1: TEdit;
    procedure amActivate(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure ComboBox1KeyPress(Sender: TObject; var Key: Char);
    procedure Edit1KeyPress(Sender: TObject; var Key: Char);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2:TForm2;
  times:integer=0;
implementation

{$R *.dfm}

procedure TForm2.amActivate(Sender: TObject);
var
name:String;
begin
     ADOQuery.Close;
     ADOQuery.SQL.Clear;
     ADOQuery.SQL.Add('select * from czyb');
     ADOQuery.Open;
         combobox1.Clear ;
     while NOT ADOQuery.Eof DO
     begin
          name:=ADOQuery.FieldByName('用户名').AsString;
           ComboBox1.Items.Add(name);
           ADOQuery.Next;
       end;
       ComboBox1.Text:='请输入用户名';
       ComboBox1.SelectAll;
end;

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

procedure TForm2.Button1Click(Sender: TObject);
var
   name:String;
   password:String;
   sqlstring:String;
begin
   inc(times);
   name:=ComboBox1.Text;
   password:=edit1.Text;
   sqlstring:='select * from czyb where 用户名='''+name+'''and 密码='''+password+'''';
   ADOQuery.Close;
   ADOQuery.SQL.Clear;
   ADOQuery.SQL.Add(sqlstring);
   ADOQuery.Open;
   if NOT ADOQuery.Eof then
    Begin
    Messagedlg('你是合法用户!',mtInformation,[mbOK],0);
    form2.Close;
    end
     else
        Begin
         Messagedlg('用户名或密码错误!',mtwarning,[mbok],0);
         ADOQuery.Close;
         if times>=3 then
         begin
          Messagedlg(Chr(13)+'登录错误次数超过3次,请下次登录！',mterror,[mbok],0);
          application.Terminate;
         end;
         combobox1.SetFocus;
        end;
end;

procedure TForm2.ComboBox1KeyPress(Sender: TObject; var Key: Char);
begin
      if key=#13 then
   begin
     postmessage(self.handle,wm_keydown,vk_tab,0);
   end;
end;

procedure TForm2.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
     if key=#13 then
  begin
    postmessage(self.handle,wm_keydown,vk_tab,0);
  end;
end;

end.