Preventing the application close

Q: I want to prevent the user from closing the application. When windows closes I want the application to do some tasks then close and then windows close.

Answer:

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    btnCloseAllow: TButton;
    btnCloseDecline: TButton;
    procedure FormCreate(Sender: TObject);
    procedure btnCloseAllowClick(Sender: TObject);
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
    procedure btnCloseDeclineClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  IsCloseAllowed: Boolean;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  IsCloseAllowed := False;
end;

procedure TForm1.btnCloseAllowClick(Sender: TObject);
begin
  IsCloseAllowed := True;
end;

procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
  CanClose := IsCloseAllowed;
end;

procedure TForm1.btnCloseDeclineClick(Sender: TObject);
begin
  IsCloseAllowed := False;
end;

end.

Author: Oktay Sancak