Simplest is subjective. What follow is my view:

#include <vcclr.h>

wchar_t __pin *pStr =  PtrToStringChars(s);

Note that .Net uses 16 bit (UNICODE) characters.

char __nogc *p;
System::String *s;

s = new String(p, 0, lstrlen(p));

Regards,
Will

Hi =?Utf-8?B?RnJhbmsgUiBFaWQ=?=,

See: Convert from System::String* to TCHAR*/CString
http://blog.kalmbachnet.de/?postid=18

The natural candidate is wchar_t * (or better wstring). In both cases
String provides a member function ToCharArray that returns a managed,
*non-null-terminated*, wchar_t array.

You can do this for example:

#using <mscorlib.dll>

#include <string>

int main()
{
    using namespace std;
    using namespace System;

    String *S= __gc new String("Some string");

    wchar_t __pin *temp= &(S->ToCharArray())[0];

    wchar_t *p=temp;

    wstring s(p, p+3);

    temp=0;
}

In your case where you want to copy it in a char * you can do this:

#using <mscorlib.dll>

int main()
{
    using namespace System;

    String *S= __gc new String("Some string");

    // Unmanaged char array in the heap
    char *pchar= new char[S->Length+1];

    wchar_t __pin *temp= &(S->ToCharArray())[0];

    for(long i=0; i<S->Length; ++i)
       pchar[i]= temp[i];

    pchar[S->Length]='\0';

   // Unpin
    temp=0;
}

The opposite is easy:

#using <mscorlib.dll>

int main()
{
    using namespace System;

    char sometext[]= "Some Text";

    String *S= __gc new String(sometext);
}

No problems, apart from when using them with managed types (like a
vector<Button *>). This will become easier in VC++ 2005.