Convert String^ to const char*

Question

Haven't used Windows Form in a very long time and this is my first time using it in C++.

And so it's the first time I've encountered the use of ^ after data types and class objects, for example:

Void Form1::btnConvert_Click(System::Object^  sender, System::EventArgs^  e)

spooky stuff.

I'm trying to call a function which requires a long pointer to constant string, so const char* or LPCSTR.

const char* cPath = txtBoxPath->Text.c_str();

The problem is when I try to convert from string^ I receive the error:

error C2228: left of '.c_str' must have class/struct/union
          type is 'System::String ^'
          did you intend to use '->' instead?

So, now I'm in a bit of a pickle. Any suggestions? Maybe educate me a bit on this ^ symbol, cause I don't seem to find anything on it when googling.

Answer 1

You can convert the System::String to a std::string via:

// Requires:
#include <msclr/marshal_cppstd.h>

auto str = msclr::interop::marshal_as<std::string>(txtBoxPath->Text);

Once you have a std::string , then c_str() will provide you the const char* :

const char* cPath = str.c_str();

Note that you can also use Marshal to do the conversion directly, ie:

IntPtr tmpHandle = Marshal::StringToHGlobalAnsi(txtBoxPath->Text);
char *cPath = static_cast<char*>(tmpHandle.ToPointer());

// use cPath

Marshal::FreeHGlobal(tmpHandle); // Don't use cPath after this...

Answer 2

The ^ character denotes a managed pointer (or reference). txtBoxPath::Text is a reference of type System::String. You'll need to de-reference it to use the dot operator or just use ->.

For the System::String^ to char* try the following:

char* cPath = (char*)Marshal::StringToHGlobalAnsi(txtBoxPath->Text).ToPointer();