ANSI转UTF-8 MFC

CString m_UserName;

DWORD DUserName;
 DUserName=::MultiByteToWideChar(CP_ACP,0,m_UserName,-1,NULL,0);
 wchar_t* WUserName = new wchar_t[DUserName];
 ::MultiByteToWideChar( CP_ACP, NULL, m_UserName, -1, WUserName, DUserName );
 DWORD uLen = ::WideCharToMultiByte( CP_UTF8, NULL, WUserName,wcslen(WUserName), NULL, 0, NULL, FALSE );
 char* uStr = new char[uLen+1];
 ::WideCharToMultiByte( CP_UTF8, NULL, WUserName,wcslen(WUserName), uStr, uLen, NULL, FALSE );
 uStr[uLen] = '\0';
 m_UserName.Format("%s",uStr);
 delete WUserName;
 delete uStr;