C convert from 1 char to string

Question

I simply need to cast one character to string. 

The inverse method is as easy as str[0].

The following suggestions did not work for me:

char c = 34;
string(1,c);
//this doesn't work, the string is always empty.

string s(c);
//also doesn't work.

boost::lexical_cast<string>((int)c);
//also doesn't work.