德尔福2010 RTTI-RttiContext.FindType

与 RttiContext.FindType('Classes.TStringList') RttiContext.FindType('MyUnit.TMyClass') 我总是得到零(当然我的单位在uses子句中)。怎么了,怎么了?

例子:

unit MyUnit; 
interface 
uses 
  Classes; 
type 
  TMyClass = class(TStringList) 
  end; 
implementation 
end. 

Main unit: 
... 
uses 
  MyUnit,
... 
var 
  oCont: TRttiContext; 
  oType: TRttiType; 
begin 
  oCont := TRttiContext.Create; 
  try 
    oType := oCont.FindType('MyUnit.TMyClass'); <== oType = nil !! 
...