C++ :: Storing A Class With String Members Into Binary Files

Im trying to make a c++ program for a school project, and i need to store the information into binary files, but I'm having some problems trying to store a class with string members, for example:

class whatever{
protected:
string name;
public:
(List of functions)
}

But if I do that, my code just dont work when I write and read a binary file, but if I change the string to char array, for example:

class whatever{
protected:
char name[20];
public:
(List of functions)
}

It works good, so I wanted to know if there's some way to store a class wiht strings in binary files, or what am I doing wrong?