如何在运行时的Form上画出如设计时期的选择多个控件的虚框

实现方法，就是使用TShape控件。实现代码如下：

unit UnitMain;

interface

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

type
TForm1 = class(TForm)
Label1: TLabel;
Button1: TButton;
Memo1: TMemo;
Shape1: TShape;
procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
pStart : TPoint;

implementation

{$R *.dfm}

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
pStart.X := X;
pStart.Y := Y;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
if Shift = [ssLeft] then
begin
Shape1.Visible := True;
Shape1.Left := pStart.X;
Shape1.Top := pStart.Y;
Shape1.Height := Y - pStart.Y;
Shape1.Width := X - pStart.X;
end;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
Shape1.Visible := False;
end;

end.