What's the problem with this Overloading statement?

Well, for a start you can't just cast a std::string to a char * like that. It's a nonsensical cast since there is no cast operator supported that will give you a pointer to the strings internal string buffer. If you are using C++11 you can get a mutable pointer to the strings internal buffer using &inString[0] but this is unsafe in earlier versions of C++. For them you'd have to use a vector as a buffer.

Secondly, what are you trying to do read or write? You seem to have a mixture of semantics going on. This should be a write, in which case this should be all you need.

BinaryStream& operator<<(BinaryStream &bStream,   const std::string& inString )
{
        return bStream << inString;
}

Well sorry for writing the question wrongly. This is the one that I am getting an error.

BinaryStream& operator<<(BinaryStream &bStream,   const std::string& inString )
    {
        std::string tempString(inString);

****        write(reinterpret_cast<char*>(&tempString.c_str()),  inString.length());

        return bStream;
    }

Actually what wew do is creating a wrapper class called BinaryStream in which we are maintaining a stringstream object. So the write() function above simply use the stringstream.write().

I am still getting an error at **** inspite of using c_str()

Thank You!