MDI程序

var
  currentcount:integer;
  ishaveinstance:boolean;
begin
  ishaveinstance:=false;
  for currentcount:=0 to MDIChildcount-1 do
  begin
     if  MDIChildren[currentcount].ClassName='Tcardfrm' then
     begin
        ishaveinstance:=true;
        MDIChildren[currentcount].WindowState:=wsmaximized;
     end;
  end;
  if not ishaveinstance then    Tcardfrm.create(self);
      begin
         icnewuserfrm := Ticnewuserfrm.Create(Application);
         icNewUserfrm.ShowModal;
         icnewuserfrm.Free; 
      end;
  end;
end;