What's the type of Stringvar? Is a MFC string, std::string or Dot Net
If Stringvar is a dot net String you do not have to create another string
with gcnew, just assign it to r->default;
If Stringvar is a Dot Net String you do not have to worry about its
lifetime, it is managed by GC. Dot net strings are managed by reference,
so technically you are coping a pointer, and it is ok.