cannot convert parameter 1 from 'System::String __gc *' to 'LPCSTR'

[ee01ppa]

Hi,

I am trying to pass comport name via combobox in managed c++.net but cant seen to get it to work. It returns with the erro message
cannot convert parameter 1 from 'System::String __gc *' to 'LPCSTR'

Can someone help me

This is my function.

String * commPort = commPortsBox->Items->Item[i]->ToString();


HANDLE hCom= ::CreateFile(commPort,GENERIC_WRITE | GENERIC_READ,0,NULL,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,NULL);


Thanks.

[ee01ppa]

I have managed to get it working.

System::String * str = commPortsBox->Items->Item[i]->ToString();
char* str2 = (char*)(void*)Marshal::StringToHGlobalAnsi(str);

HANDLE hCom= ::CreateFile(str2 ,GENERIC_WRITE | GENERIC_READ,0,NULL,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,NULL);

Thanks.

[cilu]

See this article http://support.microsoft.com/default.aspx?scid=kb;EN-US;311259

[darwen]

I have managed to get it working.

System::String * str = commPortsBox->Items->Item[i]->ToString();
char* str2 = (char*)(void*)Marshal::StringToHGlobalAnsi(str);

HANDLE hCom= ::CreateFile(str2 ,GENERIC_WRITE | GENERIC_READ,0,NULL,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,NULL);


Firstly, you're not releasing the memory you're allocating - and even worse it's global memory causing a global memory leak.

Secondly, this is a huge amount of effort for what is effectively a very simple operation.

See my article here. (http://www.codeguru.com/Cpp/Cpp/cpp_managed/moving/article.php/c8031/)

Darwen.

[ee01ppa]

@ darwen

I have changed the code to as per your suggestion. 'Marshal::FreeHGlobal(commName)' has been used to free the memory. Is there anything wrong with this code as it stands?

System::String * comm = commPortsBox->SelectedItem->ToString();
char* commName = (char*)(void*)Marshal::StringToHGlobalAnsi(comm);

HANDLE hCom= ::CreateFile(commName,GENERIC_WRITE | GENERIC_READ,0,NULL,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,NULL);

Marshal::FreeHGlobal(commName);

[darwen]

It's ok as it stands however I prefer to do it as I've said in the article as this doesn't use global memory.

Darwen.