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

  • Thread starter Thread starter ppcdev
  • Start date Start date
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ppcdev

Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::StringToHGlobalUni(str);

c:\MyNetPrj\Prj0001\stunt.cpp(244): error C2440: 'type cast' : cannot
convert from 'System::IntPtr' to 'LPCWSTR'


I really get mad with that !!!

thanks
 
ppcdev said:
Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::StringToHGlobalUni(str);
Click to expand...

try
LPCTSTR string2 =
reinterpret_cast<LPCTSTR>(Marshal::StringToHGlobalAnsi(ret).ToPointer());

don't forget to use FreeHGlobal when done.

hth
Ben
 
try
LPCTSTR string2 =
reinterpret_cast<LPCTSTR>(Marshal::StringToHGlobalAnsi(ret).ToPointer());

don't forget to use FreeHGlobal when done.
Click to expand...


for completeness:

String^ testString = gcnew String("Test");
IntPtr ptr = Marshal::StringToHGlobalAnsi(testString);
LPCTSTR string = reinterpret_cast<LPCTSTR>(ptr.ToPointer());

//do stuff with string

Marshal::FreeHGlobal(ptr);


Ben
 
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 = PtrToStringChars( 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 = PtrToStringChars( source );

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

}

target = ch;

delete ch;

return result;

}
 
ppcdev said:
Here's what I try :

LPCTSTR tst = (LPCTSTR) (LPCWSTR) Marshal::StringToHGlobalUni(str);

c:\MyNetPrj\Prj0001\stunt.cpp(244): error C2440: 'type cast' : cannot
convert from 'System::IntPtr' to 'LPCWSTR'

I really get mad with that !!!

thanks
Click to expand...

// Implementation
#include <string>
std::string convert(System::String * s)
{
const char * c = (const char
*)(System::Runtime::InteropServices::Marshal::StringToHGlobalAnsi(s)).ToPointer();
std::string str = c;
System::Runtime::InteropServices::Marshal::FreeHGlobal(System::IntPtr((void
*)c));
return str;
}


// Usage:

LPCTSTR tst = convert(str).c_str();
 
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
 
// Implementation
#include <string>
std::string convert(System::String * s)
{
const char * c = (const char
*)(System::Runtime::InteropServices::Marshal::StringToHGlobalAnsi(s)).ToPointer();
std::string str = c;
System::Runtime::InteropServices::Marshal::FreeHGlobal(System::IntPtr((void
*)c));
return str;
}


// Usage:

LPCTSTR tst = convert(str).c_str();
Click to expand...

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

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

Tom
Click to expand...

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(LPCTSTR input);
SomeFunc(convert(str).c_str());

(persistent)
std::string s = convert(str);
 
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