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In Visual C++, you can call release on a COM object and make sure the
library gets freed by calling CoFreeAllLibraries. I need to do
something similar in Visual Basic. I need to be able to load the
library I need dynamically when I need to use it and release the dll
when I'm done using the object. Does anyone know how this is done in
Visual Basic?
Thanks.
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Hi
I believe you can set the VB object reference to Nothing (or it might be Null) - that'll be equivalent to calling Release.
As for CoFreeAllLibraries, you can import that as a standard Win32 API call, in case VB doesn't supply a friendly version.
HTH
Martin
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You realize that CoFreeAllLibraries unloads _all_ dlls loaded by the COM runtime whether they are in use or not?
Quote from MSDN:
Frees all the DLLs that have been loaded with the CoLoadLibrary function (called internally by CoGetClassObject), regardless of whether they are currently in use.
This is a rather drastic thing to do and it can certainly leads to access violations and other undefined behavior.
Perhaps you intended CoFreeUnusedLibraries? I'm no VB expert but this should do the trick:
Private Declare Sub CoFreeUnusedLibraries Lib "ole32" ()
Now you should be able to call CoFreeUnusedLibraries from VB
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just a note - CoFreeUnusedLibraries takes about 10 minutes before actually releasing the dll. That got me some time ago 
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Thanks for the replies! I got it working with CoFreeUnusedLibraries after setting th e object to Nothing. Yes, you are right that it normally takes 10 minutes for the library to actually get unloaded. There are work arounds to this though: http://support.microsoft.com/kb/q301357/
I reload and unload the dll multiple times throughout the life of the program, and to do this more often than 10 minute intervals, I have a function to load the object, a function to set the object to Nothing for when I'm not using it, and a timer that calls CoFreeUnusedLibraries ever minute or so.
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Yes moron, the boards work!
--
I got nasty habits. I take tea at three.
-- Mick Jagger
I blog too now[^]
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you got a good sense of humour
modified 21-Apr-21 21:01pm.
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Thanks for recognizing it :->
--
Komm tu mir langsam weh, leg mir die Ketten an
und zieh die Knoten fest, damit ich lachen kann
I blog too now[^]
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Hi friends i was wondering if any of u would know the answer to these questions :
1. When deploying new versions of COM objects in Visual Basic, or Visual C++, often times IIS will lock the object on the application server. How do you free the object so that a new version of a component can be deployed?
A. Restart the web publishing service on the IIS server
B. Reboot your desktop
C. Recompile the COM object using binary compatibility
D. Shut down the package
E. None of the above
2. After deploying a new version of a custom VB COM object, if you see the message "Server.CreateObject Failed" which of theses choices is most likely the problem?
A. IIS is locking the object
B. The Visual Basic runtime library is locking the object and IIS cannot instantiate the object
C. Binary compatibility is not set on the server
D. The component was recompiled without binary compatibility
E. B & D
F. None of the above
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I have been trying to receive event from a COM object in C++ with no success, I think I have no found the correct way to go about it (I have never used COM before), here's what I've done:
I have created a new project as an 'ATL Project', I then used the 'Implement Interface' function to add all parts of the COM object I need which generated a ton of code but in the code was the event I am trying to receive.
Firstly, am I going about this the right way now? And if I am, how do I use this new object in my application instead of the existing object?
I'm sorry if this is a stupid question but I have read about COM and searched the net etc but I just can't figure it out, I'm having real trouble understanding COM, any help is greatly appreciated.
Thanks in advance,
Dan.
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Thanks for the reply but that's not really helping me, I understand the theory on using COM (I think) and I have downloaded and played around with the example but I still can't see how I handle an event from an existing object.
Now I have a new project with the correct methods and events, how do I use it in a C project?
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Hi
To process COM events, you first have to implement an interface - this is what you've achieved by running the wizard. You'll have to create an instance of this class somewhere is your app. Secondly you'll have to pass this instance's interface to the COM object you want to listen to - typically this is done through IConnectPointContainer, etc. and associated IConnectionPoint::Advise/Unadvise methods (an observer pattern). Call QueryInterface(__uuidof(IConnectPointContainer), ...) on the object you want to listen to to see if it supports connection points.
If you're hosting an ActiveX control in an MFC application, this is easiest done with MFC's EVENT_MAP mechanism. ATL has a similar setup with SINK_MAP. Both of these MAPs hide the details of making calls to Advise and Unadvise, and the preceding discovery of IConnectPoint interfaces on the observable.
Connection Points is just one standard mechanism of binding the observer to the observable, and may or may not be supported by the object you want to listen to. Another way to achieve the same (and functionally similar) is a straight callback - the object you want to listen to has a method for registering the observer (eg. StartListening(IMyObjectsEvents *pObserver), and StopListening(...)). But since this is a more bespoke interaction, one that is less often supported. Also, since Connection Points is a generic implementation, it incurs an overhead in number of round-trips necessary to establish the 'connections', but I doubt that it's of any concern in your case.
HTH
Martin
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Thanks, I think I have now made some progress, I have now regsitered the object successfully and created the new instance within my C project without any errors, but now I get a "Not Implemented" error when I try to use any of the commands from the original object.
In my C project, I have simply replaced the ID of the original object (CrystalDesignRunTime2.Application.Net) with the ID of the new object, what else do I need to do to make the functions work?
(I have started again on this to simply make the object work before I try implementing any event handling, any help is greatly appreciated on this, it's driving me mad!)
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Hang on there; It's not required to register the event wrapper, and probably isn't going to help at all.
Let's work through this one step at a time.
Forget about the events for now.
How are you hosting this Crystal object in your application - is it an MFC app with the Crystal control dragged onto a dialog?
Martin
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The Crystal object is hosted in a C DLL (It's a plugin for another application), it is created using this code:
m_pApp.CreateInstance("CrystalDesignRunTime2.Application.Net");
(m_pApp being an IApplicationPtr)
I then open the report with this code:
m_pRep = data->m_pApp->OpenReport(reportName, varOpenType);
(m_pRep begin an IReportPtr)
I then use the Export() function from the IReportPtr to export the report as necessary.
That all works fine, how can I create an event wrapper to work as above and capture the event?
(Thanks for your help on this!)
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Hi
The following bit of code demonstrates what is possible with ATL and catching events from the MS Calendar ActiveX control;
<<<<<<<<< START OF CODE >>>>>>>>>>
// main.cpp
#define _WIN32_WINNT 0x0500 // if you want to use ::CoInitializeEx
#include <atlbase.h>
#include <atlcom.h>
#import "C:\Program Files\Microsoft Office\OFFICE11\mscal.ocx" \
rename_namespace("cal") \
raw_interfaces_only
const int CALENDAR_SOURCE_ID = 0;
class CMyCalendarEvents;
typedef IDispEventSimpleImpl<calendar_source_id, cmycalendarevents,="" &__uuidof(cal::dcalendarevents)="">
CalendarEventsImpl;
_ATL_FUNC_INFO OnNewMonthInfo = { CC_STDCALL, VT_EMPTY, 0, 0 };
class CMyCalendarEvents
: public CalendarEventsImpl
{
public:
BEGIN_SINK_MAP(CMyCalendarEvents)
SINK_ENTRY_INFO(CALENDAR_SOURCE_ID, __uuidof(cal::DCalendarEvents), 1, OnNewMonth, &OnNewMonthInfo)
END_SINK_MAP()
void __stdcall OnNewMonth()
{
_RPT0(_CRT_WARN, "## Month Changed!\n");
}
};
void main()
{
if (FAILED(::CoInitialize(0)))
return;
try
{
CMyCalendarEvents ce;
CComPtr<cal::icalendar> ptrCalendar;
HRESULT hr = ptrCalendar.CoCreateInstance(OLESTR("MSCAL.Calendar"));
_com_util::CheckError(hr);
// start listening
hr = ce.DispEventAdvise(ptrCalendar, &__uuidof(cal::DCalendarEvents));
_com_util::CheckError(hr);
hr = ptrCalendar->Today(); // OnNewMonth fires ??
_com_util::CheckError(hr);
hr = ptrCalendar->Today(); // OnNewMonth fires ??
_com_util::CheckError(hr);
// stop listening
hr = ce.DispEventUnadvise(ptrCalendar, &__uuidof(cal::DCalendarEvents));
_com_util::CheckError(hr);
hr = ptrCalendar->Today(); // OnNewMonth fires ??
_com_util::CheckError(hr);
}
catch (...)
{
// do nothing
}
::CoUninitialize();
}
<<<<<<<<< END OF CODE >>>>>>>>>>
In your case, the event sink would look different, for example, the IReportEvent::NoData handler would be (I think);
<<<<<<<<< START OF CODE >>>>>>>>>>
const int REPORT_SOURCE_ID = 0;
class CMyReportEvents;
typedef IDispEventSimpleImpl<report_source_id, cmyreportevents,="" &__uuidof(cr::ireportevent)="">
ReportEventsImpl;
_ATL_FUNC_INFO OnNoDataInfo = { CC_STDCALL, VT_EMPTY, 1, { VT_PTR | VT_BOOL } };
class CMyReportEvents
: public ReportEventsImpl
{
public:
BEGIN_SINK_MAP(CMyReportEvents)
SINK_ENTRY_INFO(REPORT_SOURCE_ID, __uuidof(cr::IReportEvent), 1, OnNoData, &OnNoDataInfo)
END_SINK_MAP()
void __stdcall OnNoData(VARIANT_BOOL *pCancel)
{
_ASSERT(false);
}
};
<<<<<<<<< END OF CODE >>>>>>>>>>
HTH
Martin
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Thanks very much for the code!
I'm a little confused, do I use this code in the C project I have (The DLL I am working on) or in the ATL project? If I use it in the ATL project, how do I use this class in my DLL.
(Sorry if I sound really stupid but I am having a really hard time understanding how I should use COM/ATL objects)
Thanks in advance!
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Chill
It's not really feasible to have 2 DLLs - you can have both, but to my mind it just confuses things too much.
The DLL that uses the COM object (eg. calling OpenReport, etc) should be the same one that provides the events object that implements the IReportEvent interface. The theory is; if you see the following in a type library;
coclass Report {
[default] interface IReport;
interface IDReport;
[default, source] dispinterface IReportEvent;
};
it means that the Report class promises to implement IReport and IDReport, but *not* IReportEvent because that's the one you need to implement and give to the Report instance (you've created) by using the Advise/Unadvise methods mentioned earlier - this is indicated with the 'source' IDL attribute.
So, the code I gave you resembles something to be put in your work DLL and replaces the need for an ATL wrapper DLL that is generated from the type library. You can use the wizard-generated ATL DLL code as a hint to what the SINK_MAP entries should look like ....a handy reference.
As an aside, if you haven't already, use OleView to inspect Crystal's CRAXDDRT20.DLL (or similar) to see what the type library looks like.
Also, get 'ATL Internals' by Brent Rector, Chris Sells - it explains all this stuff much better than I can.
Martin
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I think I'm getting somewhere at last, just two questions I can't seem to figure out, when I try to use DispEventAdvise() function of CMyReportEvents, I get the message that it "must have class/struct/union type" which is obviously because that function does not exist in the class, how do I add the function to the class? Also, I get the message that there is no default constructor available for CMyReportEvents, is there any specific code I need in the constructor or can I use an empty constructor?
Thanks in advance!
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I have worked out where my problem is, I need to declare the ReportEventsImpl properly, I have changed the code to this:
#import "C:\Program Files\Common Files\Crystal Decisions\1.0\Bin\craxddrt20.dll" rename_namespace("cr")
using namespace cr;
const int REPORT_SOURCE_ID = 0;
class CMyReportEvents;
typedef IDispEventSimpleImpl<report_source_id, cmyreportevents,="" &cr::ireportevent=""> ReportEventsImpl;
_ATL_FUNC_INFO OnNoDataInfo = { CC_STDCALL, VT_EMPTY, 1, { VT_PTR | VT_BOOL } };
class CMyReportEvents : public ReportEventsImpl
{
public:
BEGIN_SINK_MAP(CMyReportEvents)
SINK_ENTRY_INFO(REPORT_SOURCE_ID, __uuidof(IReportEvent), 1, OnNoData, &OnNoDataInfo)
END_SINK_MAP()
bool CMyReportEvents()
{
}
void __stdcall OnNoData(VARIANT_BOOL *pCancel)
{
_ASSERT(false);
}
};
I get the error that using "IReportEvent" in the typedef and that "Use of template requires argument list", could you point me in the direction of what I use instead of IReportEvent.
Thanks!
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Hi
It's the declaration of ReportEventsImpl;
typedef IDispEventSimpleImpl ReportEventsImpl;
IDispEventSimpleImpl is a template class, so it requires parameters (source id, class, events IID), like so;
class CMyReportEvents;
typedef IDispEventSimpleImpl<report_source_id, cmyreportevents,
="" &__uuidof(cr::ireportevent)="">
ReportEventsImpl;
(note the forward declaration of CMyReportEvents)
just mail mkoorts@postmaster.co.uk directly and we can take this offline.
Martin
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Any OLE clipboard experts out there? I'm seeing some odd behavior when pasting and embedding an object in Word 2003.
Here's the scenario: in my MFC application, I paste data to the clipboard in a handful of formats - the typical OLE document crew of Embed Source, Object Discriptor, and CF_METAFILEPICT; and a CF_DIB (which seems to have no bearing on the problem). When I paste into Word 2003, an instance of my app is launched, and the embedded data is serialized in. This wouldn't bother me so much if the instance would go away after I close Word. It reeks of a reference counting issue, yes, but I'm wondering why my app is being launched in the first place. The embedded object isn't active, and Word only needs a metafile to render the object's presentation - and the metafile is readily available on the clipboard.
The odd part about this is that no additional app instance is launched when I do the same thing under Word 2000. Any clues as to what's going on here? Is Word '03 looking for a different clipboard format, or otherwise handling clipboard operations differently than Word '00? Of course, my app may be buggy  , but there haven't been issues until the '03 suite.
Any help is appreciated.
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