Getting a CString

[Stephen Engle]

I am attempting to write a C# program that accesses a C++ library. The
library has functions that return CStrings. So far I have not been able to
find a way to declare the function prototype in C# such that it will work.

For instance, I have tried declaring the function as a string type but when
I call the function, it errors out with the following:

An unhandled exception of type 'System.NullReferenceException' occurred in
TestDLM.exe

Additional information: Object reference not set to an instance of an
object.

I have tried a couple other declarations with no better results.

Does anyone have any advice?

Thanks.

[James Curran]

I don't think there's anyway to get C# to recognize a CString. I'd ssay
your best bet is to write a wrapper for the C++ library in Managed C++,
which will convert the CStrings to System.Strings

--
--
Truth,
James Curran
[erstwhile VC++ MVP]

Home: www.noveltheory.com Work: www.njtheater.com
Blog: www.honestillusion.com Day Job: www.partsearch.com

"Stephen Engle" <en***********@aoins.com> wrote in message
news:eu**************@TK2MSFTNGP09.phx.gbl...

I am attempting to write a C# program that accesses a C++ library. The
library has functions that return CStrings. So far I have not been able to find a way to declare the function prototype in C# such that it will work.

For instance, I have tried declaring the function as a string type but when I call the function, it errors out with the following:

An unhandled exception of type 'System.NullReferenceException' occurred in
TestDLM.exe

Additional information: Object reference not set to an instance of an
object.

I have tried a couple other declarations with no better results.

Does anyone have any advice?

Thanks.

[Bruce Wood]

Here is an example from my GDI32.cs:
[DllImport("winspool.drv", CharSet=CharSet.Auto)]
static extern bool OpenPrinter(
[MarshalAs(UnmanagedType.LPTStr)] string printerName,
out IntPtr printerHandle, IntPtr printerDefaults);

[Bruce Wood]

Oh, crap. I just saw that you said your library _returns_ CStrings, not
accepts them. Sorry for the brain-dead post. :-(

[Stephen Engle]

Thanks. I went with what you posted and that worked well.
"James Curran" <ja*********@mvps.org> wrote in message
news:uX**************@TK2MSFTNGP09.phx.gbl...

I don't think there's anyway to get C# to recognize a CString. I'd ssay your best bet is to write a wrapper for the C++ library in Managed C++,
which will convert the CStrings to System.Strings

--
--
Truth,
James Curran
[erstwhile VC++ MVP]

Home: www.noveltheory.com Work: www.njtheater.com
Blog: www.honestillusion.com Day Job: www.partsearch.com

"Stephen Engle" <en***********@aoins.com> wrote in message
news:eu**************@TK2MSFTNGP09.phx.gbl...

I am attempting to write a C# program that accesses a C++ library. The
library has functions that return CStrings. So far I have not been able

to

find a way to declare the function prototype in C# such that it will work.
For instance, I have tried declaring the function as a string type but

when

I call the function, it errors out with the following:

An unhandled exception of type 'System.NullReferenceException' occurred in TestDLM.exe

Additional information: Object reference not set to an instance of an
object.

I have tried a couple other declarations with no better results.

Does anyone have any advice?

Thanks.