CRichEditCtrl采用StreamIn和StreamOut打开文档怎么是空白呀????????????????????????????

单文挡\5步选window explore\6步选CRichEditView
在工具栏添加保存(ID_SAVE)和打开(ID_OPEN),然后驱动相应函数OnSave\OnOpen
怎么能够保存,打开确是空白?
添加代码如下:static DWORD CALLBACK MyStreamOutCallback(DWORD dwCookie, LPBYTE pbBuff, LONG cb, LONG *pcb)
{
   CFile* pFile = (CFile*) dwCookie;   pFile->Write(pbBuff, cb);
   *pcb = cb;   return 0;
}static DWORD CALLBACK MyStreamInCallback(DWORD dwCookie, LPBYTE pbBuff, LONG cb, LONG *pcb)
{
   CFile* pFile = (CFile*) dwCookie;   pFile->Read(pbBuff, cb);
   *pcb = cb;   return 0;
}void CTestEditView::OnSave() 
{
   CRichEditCtrl & pmyRichEditCtrl = GetRichEditCtrl();   
   CFile cFile(TEXT("my.txt"), CFile::modeCreate|CFile::modeReadWrite);
   EDITSTREAM es;
   es.dwCookie = (DWORD) &cFile;
   es.pfnCallback = MyStreamOutCallback; 
   pmyRichEditCtrl.StreamOut(SF_TEXTIZED, es);
}void CTestEditView::OnOpen() 
{
   CRichEditCtrl & pmyRichEditCtrl = GetRichEditCtrl();   
   CFile cFile(TEXT("my.txt"), CFile::modeReadWrite);
   EDITSTREAM es;
   es.dwCookie = (DWORD) &cFile;
   es.pfnCallback = MyStreamInCallback; 
   pmyRichEditCtrl.StreamIn(SF_TEXTIZED, es);   

}