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How to convert String* to LPCTSTR ??? I found threads about that but don't work...

Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::String ToHGlobalUni(st r);

c:\MyNetPrj\Prj 0001\stunt.cpp( 244): error C2440: 'type cast' : cannot
convert from 'System::IntPtr ' to 'LPCWSTR'
I really get mad with that !!!

thanks
Nov 17 '05 #1
8 12175
using StringToHGlobal Ansi should return a LPCTSTR.

"ppcdev" <pp****@hotmail .com> wrote in message
news:2f******** *************** ***@posting.goo gle.com...
Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::String ToHGlobalUni(st r);

c:\MyNetPrj\Prj 0001\stunt.cpp( 244): error C2440: 'type cast' : cannot
convert from 'System::IntPtr ' to 'LPCWSTR'
I really get mad with that !!!

thanks

Nov 17 '05 #2
ppcdev wrote:
Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::String ToHGlobalUni(st r);


try
LPCTSTR string2 =
reinterpret_cas t<LPCTSTR>(Mars hal::StringToHG lobalAnsi(ret). ToPointer());

don't forget to use FreeHGlobal when done.

hth
Ben
Nov 17 '05 #3
> try
LPCTSTR string2 =
reinterpret_cas t<LPCTSTR>(Mars hal::StringToHG lobalAnsi(ret). ToPointer());

don't forget to use FreeHGlobal when done.

for completeness:

String^ testString = gcnew String("Test");
IntPtr ptr = Marshal::String ToHGlobalAnsi(t estString);
LPCTSTR string = reinterpret_cas t<LPCTSTR>(ptr. ToPointer());

//do stuff with string

Marshal::FreeHG lobal(ptr);
Ben
Nov 17 '05 #4
and here's a different method taken from Stan Lippman's blog
(http://weblogs.asp.net/slippman/).

this converts to a char array, which you should easily be able to
convert to LPTCSTR

note that vcclr.h is included

#include <stdlib.h>
#include <vcclr.h>
#include <string>
using namespace System;

bool To_CharStar( String^ source, char*& target )
{
int len = (( source->Length+1) * 2);
target = new char[ len ];
pin_ptr<const wchar_t> wch = PtrToStringChar s( source );
return wcstombs( target, wch, len ) != -1;
}

bool To_string( String^ source, string &target )

{

int len = (( source->Length+1) * 2);

char *ch = new char[ len ];

bool result ;

{

pin_ptr<const wchar_t> wch = PtrToStringChar s( source );

result = wcstombs( ch, wch, len ) != -1;

}

target = ch;

delete ch;

return result;

}
Nov 17 '05 #5
ppcdev wrote:

Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::String ToHGlobalUni(st r);

c:\MyNetPrj\Prj 0001\stunt.cpp( 244): error C2440: 'type cast' : cannot
convert from 'System::IntPtr ' to 'LPCWSTR'

I really get mad with that !!!

thanks


// Implementation
#include <string>
std::string convert(System: :String * s)
{
const char * c = (const char
*)(System::Runt ime::InteropSer vices::Marshal: :StringToHGloba lAnsi(s)).ToPoi nter();
std::string str = c;
System::Runtime ::InteropServic es::Marshal::Fr eeHGlobal(Syste m::IntPtr((void
*)c));
return str;
}
// Usage:

LPCTSTR tst = convert(str).c_ str();
Nov 17 '05 #6
Thank you very much for your help that I've read only today !!!
I've also found an alternative using the wsprintf("%S".. .) function...

see you

Julie <ju***@nospam.c om> wrote in message news:<40******* ********@nospam .com>...
ppcdev wrote:

Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::String ToHGlobalUni(st r);

c:\MyNetPrj\Prj 0001\stunt.cpp( 244): error C2440: 'type cast' : cannot
convert from 'System::IntPtr ' to 'LPCWSTR'

I really get mad with that !!!

thanks


// Implementation
#include <string>
std::string convert(System: :String * s)
{
const char * c = (const char
*)(System::Runt ime::InteropSer vices::Marshal: :StringToHGloba lAnsi(s)).ToPoi nter();
std::string str = c;
System::Runtime ::InteropServic es::Marshal::Fr eeHGlobal(Syste m::IntPtr((void
*)c));
return str;
}
// Usage:

LPCTSTR tst = convert(str).c_ str();

Nov 17 '05 #7
On Tue, 06 Jul 2004 12:20:29 -0700, Julie <ju***@nospam.c om> wrote:
ppcdev wrote:

Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::String ToHGlobalUni(st r);

c:\MyNetPrj\Prj 0001\stunt.cpp( 244): error C2440: 'type cast' : cannot
convert from 'System::IntPtr ' to 'LPCWSTR'

I really get mad with that !!!

thanks


// Implementation
#include <string>
std::string convert(System: :String * s)
{
const char * c = (const char
*)(System::Run time::InteropSe rvices::Marshal ::StringToHGlob alAnsi(s)).ToPo inter();
std::string str = c;
System::Runtime ::InteropServic es::Marshal::Fr eeHGlobal(Syste m::IntPtr((void
*)c));
return str;
}
// Usage:

LPCTSTR tst = convert(str).c_ str();


That has the same problem as the original code - tst becomes a
dangling pointer straight after the ;.

Tom
Nov 17 '05 #8
tom_usenet wrote:

On Tue, 06 Jul 2004 12:20:29 -0700, Julie <ju***@nospam.c om> wrote:
ppcdev wrote:

Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::String ToHGlobalUni(st r);

c:\MyNetPrj\Prj 0001\stunt.cpp( 244): error C2440: 'type cast' : cannot
convert from 'System::IntPtr ' to 'LPCWSTR'

I really get mad with that !!!

thanks


// Implementation
#include <string>
std::string convert(System: :String * s)
{
const char * c = (const char
*)(System::Run time::InteropSe rvices::Marshal ::StringToHGlob alAnsi(s)).ToPo inter();
std::string str = c;
System::Runtime ::InteropServic es::Marshal::Fr eeHGlobal(Syste m::IntPtr((void
*)c));
return str;
}
// Usage:

LPCTSTR tst = convert(str).c_ str();


That has the same problem as the original code - tst becomes a
dangling pointer straight after the ;.

Tom


Duh, right.

I use it in function calls, and never keep a pointer around to the underlying
c_str(), it was merely for (flawed!) illustrative purposes, thanks for pointing
it out.

Updated usage:

(immediate)

void SomeFunc(LPCTST R input);
SomeFunc(conver t(str).c_str()) ;

(persistent)
std::string s = convert(str);
Nov 17 '05 #9

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