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.NullRef erenceException ' 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]

Re: Getting a CString

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" <engle.stephen@ aoins.com> wrote in message
news:euK0YocSFH A.2520@TK2MSFTN GP09.phx.gbl...[color=blue]
> 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[/color]
to[color=blue]
> 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[/color]
when[color=blue]
> I call the function, it errors out with the following:
>
> An unhandled exception of type 'System.NullRef erenceException ' 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.
>
>[/color]

[Bruce Wood]

Re: Getting a CString

Here is an example from my GDI32.cs:


[DllImport("wins pool.drv", CharSet=CharSet .Auto)]
static extern bool OpenPrinter(
[MarshalAs(Unman agedType.LPTStr )] string printerName,
out IntPtr printerHandle, IntPtr printerDefaults );

[Bruce Wood]

Re: Getting a CString

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

[Stephen Engle]

Re: Getting a CString

Thanks. I went with what you posted and that worked well.


"James Curran" <jamescurran@mv ps.org> wrote in message
news:uXhqQxcSFH A.2520@TK2MSFTN GP09.phx.gbl...[color=blue]
> I don't think there's anyway to get C# to recognize a CString. I'd[/color]
ssay[color=blue]
> 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" <engle.stephen@ aoins.com> wrote in message
> news:euK0YocSFH A.2520@TK2MSFTN GP09.phx.gbl...[color=green]
> > 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[/color]
> to[color=green]
> > find a way to declare the function prototype in C# such that it will[/color][/color]
work.[color=blue][color=green]
> >
> > For instance, I have tried declaring the function as a string type but[/color]
> when[color=green]
> > I call the function, it errors out with the following:
> >
> > An unhandled exception of type 'System.NullRef erenceException ' occurred[/color][/color]
in[color=blue][color=green]
> > 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.
> >
> >[/color]
>
>[/color]