A reader asks,

 

Sender: Erik Brendengen

 

Is there an easy way to convert from String^ to std::string?

             Does String ^s = std::string( “bla”).c_str(); work the other way?

 

This is a FAQ, one that I myself bumped into when I had to pass a System::String retrieved from System::Windows::Forms::TextBox to a native program that expected a std::string.

 

There are generally two conversion strategies, depending on which side of the managed/native fence you wish to do the conversion work. Here are two methods making use of the PtrToStringChars( String^ ) utility from the vcclr.h header file that is part of Visual C++. Note that these are written in the new C++/CLI syntax – and that these are adapted from an internal FAQ ...

 

#include <stdlib.h>
#include <vcclr.h>
#include <string>
using namespace System;
 
bool To_CharStar( String^ source, char*& target )
{
    pin_ptr<const wchar_t> wch = PtrToStringChars( source );
    int len = (( source->Length+1) * 2);
    target = new char[ len ];
    return wcstombs( target, wch, len ) != -1;
}
 
bool To_string( String^ source, string &target )
{
    pin_ptr<const wchar_t> wch = PtrToStringChars( source );
    int len = (( source->Length+1) * 2);
    char *ch = new char[ len ];
    bool result = wcstombs( ch, wch, len ) != -1;
    target = ch;
    delete ch;
    return result;
}

 

As to the second question, does String^ s = ns.c_str() work? Yes.