IDirectorySearch GetColumn不返回实际数据（C ++）

Question

我尝试使用IDirectorySearch从Active Directory中读取一些属性值。 当我运行本地程序时，代码工作正常。我写了IIS7扩展和我的代码运行到w3wp.exe。当代码运行到w3wp.exe时，ExecuteSearch方法找到我需要的东西，但GetColumn只返回pszAttrName和dwADsType。在pADsValues中，我看到错误的值（或未初始化的）

代码：

std::string strFromHex(BYTE* data, int length)
{
   std::stringstream ss;

   ss << std::hex;

   for( size_t i=0;i != length; ++i )
      ss << (size_t)data[i];

   return ss.str();
}    

std::string GetGUID()
{    
   std::string guid;
   IDirectorySearch* dSearch;
   hr = ADsOpenObject(L"LDAP://DOMEN", L"UserLogin", L"UserPass", ADS_SECURE_AUTHENTICATION, IID_IDirectorySearch, (void**)&dSearch);

   if(FAILED(hr))
      return guid;

   LPWSTR searchFilter = L"(&(objectClass=user)(| (userPrincipalName=userLogin*)))";
   LPWSTR att[] = { L"objectGUID" };
   DWORD attCount = 1;
   ADS_SEARCH_HANDLE hSearch;
   ADS_SEARCH_COLUMN col;

   hr = dSearch->ExecuteSearch( searchFilter, att, attCount, &hSearch);

   if(FAILED(hr))
      return guid;

   hr = dSearch->GetFirstRow(hSearch);
   while(S_OK == hr)
   {
      for(DWORD i = 0; i < attCount; i++)
      {
         hr = dSearch->GetColumn(hSearch, att[i], &col);
         if(SUCCEEDED(hr))
         {
            if( col.dwADsType == ADSTYPE_OCTET_STRING )
               guid = strFromHex( col.pADsValues[0].OctetString.lpValue, col.pADsValues[0].OctetString.dwLength );

            dSearch->FreeColumn(&col);
         }
      }
      hr = dSearch->GetNextRow(hSearch);
   }
   hr = dSearch->CloseSearchHandle(hSearch);

   return guid;
}