c++ - How to convert a string to a ifstream

i am trying to open a file with ifstream and i want to use a string as the path (my program makes a string path). it will compile but it stays blank.

string path = NameOfTheFile; // it would be something close to "c:\file\textfile.txt"
string line;


ifstream myfile (path); // will compile but wont do anything.
// ifstream myfile ("c:\\file\\textfile.txt"); // This works but i can't change it
if (myfile.is_open())
{
   while (! myfile.eof() )
   {
      getline (myfile,line);
      cout << line << endl;
   }
}

I am using windows 7, My compiler is VC++ 2010.

Answer

string path = compute_file_path();
ifstream myfile (path.c_str());
if (!myfile) {
  // open failed, handle that
}
else for (string line; getline(myfile, line);) {

  use(line);
}