C++ 窄字符转换为宽字符

wstring A2W(const string &s){    const char * szSource = s.c_str();    size_t _Dsize = MultiByteToWideChar(CP_ACP,0,szSource,-1,NULL,0);    wchar_t * wszDest = new wchar_t[_Dsize];    MultiByteToWideChar(CP_ACP,0,szSource,-1,wszDest,_Dsize);    wstring result = wszDest;    delete []wszDest;    return result;}