Problems w/ MapScript C#

[Sean Gillies]

On Apr 7, 2005, at 3:30 AM, Johannes Schulte Sÿfffffcdhoff wrote:

> --- Sean Gillies <sgillies at FRII.COM> wrote:
>> On Apr 6, 2005, at 3:59 PM, Morten Nielsen wrote:
>>
>>>> I've successfully built the C# Mapscript
>> assembly, and have
>>>> successfully
>>>> written code that generates an image file to
>> disk.  Everything seems
>>>> to
>>>> work just fine until I make repeated calls to the
>> map.draw() function.
>>>> I get the following exception after 3 or 4 calls
>> to the private member
>>>> function drawMapImage():
>>>
>>>> System.NullReferenceException: Object reference
>> not set to an instance
>>>> of an object.
>>>>   at mapscriptPINVOKE.mapObj_draw(IntPtr jarg1)
>>>>   at mapObj.draw()
>>>>   at SimpleMap.Form1.drawMapImage()
>>>
>>> I have lately experienced the same problem that
>> Ian has. It seems that
>>> the
>>> C#/SWIG mapscript is very unstable, no matter
>> whether it's a Windows
>>> Application or a web application. Some times it
>> works, sometimes it
>>> don't.
>>> Sometimes it always works on one machine, but
>> never on another. And
>>> sometimes it even crashes the IIS process. I
>> wonder if this also
>>> occurs on
>>> the Mono-based assemblies.
>>>
>>> The C# support in SWIG is pretty new, so it could
>> be a SWIG bug, but I
>>> wasn't ably to find any that apply in their
>> bug-tracking. Perhaps we
>>> should
>>> better start looking at the SWIG implementation,
>> although I really
>>> wouldn't
>>> know where to begin; especially because it's so
>> hard to debug.
>>>
>>> Pointers to get me started on this are highly
>> appreciated.
>>>
>>> /Morten Nielsen
>>>
>>
>> My impression is that you may be getting ahead of
>> yourselves a bit with
>> your SimpleMap and Form classes.  Let's back up a
>> bit.  Make the
>> simplest possible mapscript application, and then
>> run the web app under
>> your debugger to find out what the problem actually
>> is.  If you can't
>> debug your website, perhaps try with some sort of
>> lightweight
>> multithreading HTTP server.  The .NET platform must
>> have something like
>> this.
>>
>> That said, now I am going to take a wild swing :)
>> Any chance that
>> you've overlooked building in the win32 thread
>> support from
>> mapthread.c?  It's off by default in MapServer's
>> windows makefile and
>> never really mentioned in any of the win32
>> installation docs.
>
> Just another wild swing :-). Morten is using the
> windows binary of the gd library. Doing this you have
> to compile everything with VC6 and you have to bind
> the multithreaded dll crt. see the gd faq for more
> information
>
> /Johannes
>

Right.  Good point, Johannes.

Sean