'System::String ^' to 'LPCWSTR'

Question

Hey, I want to convert 'System::String ^' to 'LPCWSTR'.

for

FindFirstFile(LPCWSTR,WIN32_FIND_DATA);

Please help.

Answer 1

You need to use P/Invoke. Check this link: http://www.pinvoke.net/default.aspx/kernel32/FindFirstFile.html

Simply add the DllImport native function signature:

 [DllImport("kernel32.dll", CharSet=CharSet.Auto)]
 static extern IntPtr FindFirstFile
     (string lpFileName, out WIN32_FIND_DATA lpFindFileData);

and CLR will do managed to native type marshaling automatically.

[Edit] I just realized you're using C++/CLI. In that case, you can also use implicit P/Invoke, which is a feature which only C++ supports (opposed to C# and VB.NET). This articles shows several examples:

How to: Convert Between Various String Types in C++/CLI

Answer 2

To convert a System::String ot LPCWSTR in C++/CLI you can you use the Marshal::StringToHGlobalAnsi function to convert managed strings to unmanaged strings.

System::String ^str = "Hello World";

IntPtr ptr = System::Runtime::InteropServices::Marshal::StringToHGlobalAnsi(str);

HANDLE hFind = FindFirstFile((LPCSTR)ptr.ToPointer(), data);

System::Runtime::InteropServices::Marshal::FreeHGlobal(ptr);

Answer 3

The easiest way to do this in C++/CLI is to use pin_ptr:

#include <vcclr.h>

void CallFindFirstFile(System::String^ s)
{
    WIN32_FIND_DATA data;
    pin_ptr<const wchar_t> wname = PtrToStringChars(s);
    FindFirstFile(wname, &data);
}