Converting from C# string to C++ wchar_t [unmanaged]

Question

I'm working on a WinRT app in which I need to pass Device ID from C# class to C++ object. The format of ID is:

\\?\SWD#MMDEVAPI#{0.0.0.00000000}.{572cb138-dda1-4723-90d7-373f04b795fb}#{e6327cad-dcec-4949-ae8a-991e976a79d2}

This works well in C++ if I cast it as:

L"\\\\?\\SWD#MMDEVAPI#{0.0.0.00000000}.{572cb138-dda1-4723-90d7-373f04b795fb}#{e6327cad-dcec-4949-ae8a-991e976a79d2}"

However, if I pass it as System.String from C# class to C++ and cast it as LPCWSTR, it doesn't work.

C++ code:

UniversalAudioPlayer::UniversalAudioPlayer(String^ deviceID)
{
HRESULT hr = XAudio2Create(&xAudio);

if (FAILED(hr))
    ref new COMException(hr, "XAudio2Create failure");

XAUDIO2_DEBUG_CONFIGURATION debugConfig = { 0 };
debugConfig.TraceMask = XAUDIO2_LOG_DETAIL | XAUDIO2_LOG_WARNINGS;
xAudio->SetDebugConfiguration(&debugConfig);

hr = xAudio->CreateMasteringVoice(&masteringVoice, 0U, 0U, 0U, (LPCWSTR)deviceID);

if (FAILED(hr))
    ref new COMException(hr, "Could not create mastdsdering voice");

xAudio->StartEngine();
}

C# code:

UniversalAudioPlayer player = new UniversalAudioPlayer("\\\\?\\SWD#MMDEVAPI#{0.0.0.00000000}.{41a5b8e4-ad46-4bcb-b8a0-3621edafd176}#{e6327cad-dcec-4949-ae8a-991e976a79d2}");

I'm not able to include

#include < vcclr.h >

in my C++ class either as WinRT doesn't support managed assemblies.

Please suggest me any solution. Thanks in advance.

Theres an [MSDN code example](https://msdn.microsoft.com/library/d1ae6tz5(v=vs.100).aspx) for it. — Konrad 'Zegis', Dec 01 '15 at 09:57
http://stackoverflow.com/questions/1062962/systemstring-to-lpcwstr May be relevant. Please add your code so it's more clear what you're trying to do. — WiredPrairie, Dec 02 '15 at 11:43
@WiredPrairie https://msdn.microsoft.com/en-us/library/windows/desktop/hh405048(v=vs.85).aspx this is the method I want to pass szDeviceId to, from my C# class. — Muhammad Hassan, Dec 02 '15 at 13:01
OK -- and what code did you write that isn't working? How are you trying to convert from one string to another? Are you using pinning, `Marshal`, etc? — WiredPrairie, Dec 02 '15 at 13:20

score 2 · Accepted Answer · answered Dec 03 '15 at 19:19

2

You can convert from a Platform::String^ to a wchar_t* with the String::Data method.

hr = xAudio->CreateMasteringVoice(&masteringVoice, 0U, 0U, 0U, deviceID->Data);

answered Dec 03 '15 at 19:19

Rob Caplan - MSFT

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Thanks a lot. Never imagined the solution was that simple. Saved me from a big trouble. – Muhammad Hassan Dec 04 '15 at 06:17

Converting from C# string to C++ wchar_t [unmanaged]

1 Answers1