string转换为LPCWSTR

size_t sizea = str_pathexp_d.length();
wchar_t *buffera = new wchar_t[size+1];
MultiByteToWideChar( CP_ACP, 0, str_pathexp_d.c_str(), sizea, buffera, sizea * sizeof(wchar_t) );
buffera[sizea] = 0;  // 确保以 '\0' 结尾 
delete buffera;