大家帮个忙看一下好吗？(45分)

unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, Scl12, cadodraw, Markmove;
type
TForm1 = class(TForm)
cdDrawbox1: TcdDrawbox;
MarkMove1: TMarkMove;
cdLines1: TcdLines;
//线控件
procedure MarkMove1ObjectClick(CurrentObject: TcdObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.MarkMove1ObjectClick(CurrentObject: TcdObject);
begin
if (currentobject is tlineobj) then
//如果移动对象的是线
(currentobject as TcdLines)//老是过不去。
end;
我想得到传递过来的对象，然后改天这个对象的属性。怎么做呢。
end;

end.

你的tlineobj必须是TcdLines的子类才行

我怎么办呢。