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Re: Problem in adding a new function in existing Interface

Ravikr0717-Sep-07 10:25

Ravikr07

17-Sep-07 10:25

Nathan thanks for your response. But my dll is part of an existing product. Over the years according to new requirements new functions have been added to existing Interfaces. From the change history I did the same changes for a new function but got the error.
MSDN says that Interfaces are immutable, but we can modify them if version of ur dll doenst change.
I wrote an MFC COM server(an exe) which registers it self when invoked. I was able to add new functions to existing Interface.

Thanks again!

Re: Problem in adding a new function in existing Interface

Nathan Holt at EMOM17-Sep-07 11:08

Nathan Holt at EMOM

17-Sep-07 11:08

Slumberger wrote:
Nathan thanks for your response. But my dll is part of an existing product. Over the years according to new requirements new functions have been added to existing Interfaces. From the change history I did the same changes for a new function but got the error.

By adding a new interface, I don't mean remove the old one. The idea is to not break existing clients. It's interesting that you were able to get away with this sort of thing before. (Perhaps I misunderstand what you were doing.) However, I know from experience that VB6 is not reliable about handling changes. I've often had trouble getting VB to use new objects and interfaces instead of old ones.

Slumberger wrote:
MSDN says that Interfaces are immutable, but we can modify them if version of ur dll doenst change.

Do you mean the server dll, or the client dll? It's certainly not too bad if existing client dlls don't need to be changed, but VB6 is particularly bad about adapting to these changes. The main danger of modifying an interface that way is that someone might try to run a new client dll with an older server, in which the first sign that something is wrong could be when the nonexistant function is called, (and possibly not even then).

Slumberger wrote:
I wrote an MFC COM server(an exe) which registers it self when invoked. I was able to add new functions to existing Interface.

I'd expect things to work better with a .exe because of the self registering behavior. Dlls are a bit harder in that it's easy to miss registering them, and Tlbs are even worse, since it's so difficult to register them. VB6 can register a type library provided that the type library isn't already registered. This could have something to do with your problem.

Nathan

Re: Problem in adding a new function in existing Interface

Ravikr0717-Sep-07 19:37

Ravikr07

17-Sep-07 19:37

So if I add a function to an interface(existing) and get a new build and package for my product and then install it in a new machine then the new function should work?

If registering is the issue then I guess above should work.

Please correct if I am wrong anywhere.

See my problem is like this. We have a product and this dll (com server) which exposes the intefaces get registered only when the product is installed and get unregistered if we uninstall the product. So if we modify an existing interface, build the com server dll containing that interface and then prepare a fresh package for install and then install it on a new nachine then the change(adding a new function to exiting interface) should work.

thanks in advance

Re: Problem in adding a new function in existing Interface

Nathan Holt at EMOM18-Sep-07 7:24

Nathan Holt at EMOM

18-Sep-07 7:24

Slumberger wrote:
So if I add a function to an interface(existing) and get a new build and package for my product and then install it in a new machine then the new function should work?

Yes, it should work. However, if you are developing the dll in VB6, it is likely that VB changed a class ID or an interface ID when you added the new member, and that would defeat even the reinstall.

Nathan

Re: Problem in adding a new function in existing Interface

paresh_joe26-Sep-07 2:50

paresh_joe

26-Sep-07 2:50

Hi,

I am new to this COM stuff,but as i have gone through many documents would like to put some light on re-usability of Components.

as Interfaces are Immutable , you can create new Interface with additional methods you wants to add and implement Aggregation relationship with Original Interface.

Perry

Getting a ('support_error_info' : attribute not found) error

monsieur_jj16-Sep-07 21:15

monsieur_jj

16-Sep-07 21:15

Here is a snippet of my .h file

[
	coclass,
	noncreatable,
	threading(apartment),
	support_error_info("IAttachment"),
	vi_progid("RMMAPIParserLib.Attachment"),
	progid("RMMAPIParserLib.Attachment.1"),
	version(1.0),
	uuid("32ECA67C-0B5F-4489-B163-85C6CEDDB746"),
	helpstring("Attachment Class")
]

class ATL_NO_VTABLE Attachment : 
	public IAttachment
{
.....
STDMETHOD(GetPropUNICODE)(LONG PropertyID, BSTR* pRetVal);
.....
}

and here is the function

STDMETHODIMP Attachment::GetPropUNICODE(LONG PropertyID, BSTR* pRetVal)
{
	// make sure the requested property's type is unicode
	if ((PROP_TYPE_MASK & PropertyID) != PT_UNICODE)
	{
		return E_FAIL;
	}

	// find the property
	redmap::mapi::FoundProperty prop 
		= m_Attachment->FindProperty(PropertyID);

	if (prop.second)
	{
		// BSTR-convert and return the property value
		ATL::CComBSTR bstr (prop.first.lpszW);
		return bstr.CopyTo(pRetVal);
	} 
	else 
	{
		ATL::CComBSTR bstr (L"");
		return bstr.CopyTo(pRetVal);
	}
}

Now my problem is I am getting the support_error_info error, what is wrong with the code?

Thanks
Jj

Re: Getting a ('support_error_info' : attribute not found) error

Nathan Holt at EMOM17-Sep-07 10:13

Nathan Holt at EMOM

17-Sep-07 10:13

I think for the "support error info" to work, you class has to implement ISupportErrorInfo, which allows a caller to request extra information about the last error.

Nathan

AxtiveX, this pointer [modified]

m1m216-Sep-07 10:38

m1m2

16-Sep-07 10:38

Hi,
it hapend something very strange to me, when i call 'this' from inside the activeX control class, when i debug project with 'activex test container', it work fine, but when i start the release with iexplorer, when call 'this' it seems to get not activex control pointer to DC, but pointer to desktop DC. Because when iexplorer is not maximized, in the center of screen, when call 'this', it starts to write on the top left corner on the desktop, outside of iexplorer.

I get this pointer and then construct CClientDC dc(this); I tought that maybe this is null and get desktop dc, but when put condition if(){}, this is not null and enter int brckets.

Thanks.

-- modified at 2:17 Monday 17th September, 2007

Can i use a dll in an activeX component?

just3ala215-Sep-07 10:04

just3ala2

15-Sep-07 10:04

Dear all, i'm developing an activex component to use in a web application. my task requires using a dll to do some work...
When i try to add it to the references of the project i get the message of "can't add a reference to the specified file"
I'm using Visual Studio 6 and vb6 as a language

Any help or hints would be appreciated

Thanks in advance Big Grin | :-D

Best Regards
3ala2 Smile | :)

Re: Can i use a dll in an activeX component?

Nathan Holt at EMOM17-Sep-07 10:17

Nathan Holt at EMOM

17-Sep-07 10:17

just3ala2 wrote:
Dear all, i'm developing an activex component to use in a web application. my task requires using a dll to do some work...
When i try to add it to the references of the project i get the message of "can't add a reference to the specified file"
I'm using Visual Studio 6 and vb6 as a language

It sounds like you are trying to add a reference to a dll that isn't a COM dll. VB6 does provide a way to access them, but it involves creating a module file and writing code to import all the functions that you need to call in the dll.

Nathan

Re: Can i use a dll in an activeX component?

just3ala217-Sep-07 12:26

just3ala2

17-Sep-07 12:26

I c

Thanx nathan, i found another dll that does the same job and can be added as a reference Wink | ;)

Best Regards
3ala2 Smile | :)

Difference between .idl and .h file?

Ash2014-Sep-07 0:23

Ash20

14-Sep-07 0:23

Hey ,

Can you please explain the diffrence between .idl and .h file?
Also How to create a new .idl file in VC6?

Thanks,
Ash.

Re: Difference between .idl and .h file?

Hubert Mayer14-Sep-07 4:58

Hubert Mayer

14-Sep-07 4:58

The idl-File is the input for the midl-compiler which creates an _i.c and .h file for further use. See MIDL-Compiler for more information. For creation of an idl-file use the ATLCOM-wizard in the VS.

Beginner In COM facing problem

GauranG Shah13-Sep-07 23:21

GauranG Shah

13-Sep-07 23:21

I am learning COM. And has come to know about one of the Advantages of the COM over .dll file. That

It extends the functionality of (client)application without rebuilding.

I.e. If you make the changes in function of .Dll File which client application is using you need to recompile the application. But if you are using the COM you dont need to do recompilation of client application Smile | :)

But How ?? Confused | :confused:

afterall the COM ( inprocess COM) is also a .dll

Re: Beginner In COM facing problem

DevMentor.org16-Sep-07 22:34

DevMentor.org

16-Sep-07 22:34

Well you don't necessarily have to rebuild the entire app that is using a dll when it changes. Think about how Microsoft provides patches or updates to DLLs. Do you need to rebuild your OS to use the new DLLS Big Grin | :-D

As long at the function interface does not change you don't need to worry about rebuilding the app that uses the DLL.

COM provides interfaces that other app use. As long as the interface is not changed everything will be fine if the COM object has some code changes.

Let's say a code of a COM interface was modify like a bug fix, then the app using the old COM object will be able to use the new COM object because all it needs to do is CoCreate the COM object and Query for it's interface. This part remains the same in the app, so the app doesn't need to be changed.

Yours Truly, The One and Only!
---
Rajinder Yadav
devmentor.org

From where to Start......... ???

GauranG Shah13-Sep-07 2:36

GauranG Shah

13-Sep-07 2:36

I m thinking to learn COM but not getting from where to start ?. If u know about any good book please tell. If you can provide the link to the Ebook it will be gr8 HELP!.

Thnx in Advance.

Re: From where to Start......... ???

Michael Dunn13-Sep-07 10:08

Michael Dunn

13-Sep-07 10:08

Introduction to COM - What It Is and How to Use It[^]

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! Ericahist | PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

"That's what's great about doing user interface work. No matter what you do, people will say that what you did was idiotic." -- Raymond Chen

Re: From where to Start......... ???

GauranG Shah13-Sep-07 20:23

GauranG Shah

13-Sep-07 20:23

Thnx but I have already read this article b4 and other aricles from the codeproject.com. So if u know about any good Book which have explained COM in Depth please tell me.

Re: From where to Start......... ???

Michael Dunn13-Sep-07 22:15

Michael Dunn

13-Sep-07 22:15

Essential COM by Don Box.

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! Ericahist | PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

I work for Keyser Söze

Re: From where to Start......... ???

User 21559713-Sep-07 23:37

User 215597

13-Sep-07 23:37

Essential COM - by Don Box
you may also want to look at
Inside COM - by Dale Rogerson

Sohail

modified 21-Apr-21 21:01pm.

How will you talk with Activex or COM(could be created in MFC) From C#?

spalanivel12-Sep-07 21:36

spalanivel

12-Sep-07 21:36

Hi,
How will you talk with Activex or COM(could be created in MFC) From C#?
Plzz send me ur valuable suggestions to me as soon as possible...Thanks to u..What is CCW and RCW?How to use it?

spalanivel

Re: How will you talk with Activex or COM(could be created in MFC) From C#?

User 21559713-Sep-07 1:08

User 215597

13-Sep-07 1:08