Re: Shielding COM objects? - COM Discussion Boards

Sub classing a Activex Control

2-Jun-03 1:30

Never mind, I already found what I was looking for: AfxOleGetUserCtrl().

Mayank Goyal1-Jun-03 23:39

Mayank Goyal

1-Jun-03 23:39

Hi, I need to create a new Activex control by sub classing another Activex control. This will retain all the old functionality plus some other functions can also be added, i have tried doing it through the MFC ATL wizard, but that only create a wrapper araound it. Also MFC's ActiveX control wizard does seem to support sub classing of some MS standard controls only.
if you have a way to acheive this then please do help.

Mayank Goyal

Shielding COM objects?

Brian van der Beek1-Jun-03 22:06

1-Jun-03 22:06

Hi, I have an MFC application on which I want to put a COM interface so other applications can interface with my application. I succeeded in doing this, but now I have several object that can be created from outside my application. What I want is to provide a single object that creates the other objects. Can (and if so, how?) I shield these objects so they can not be created from outside my own application ?

valikac2-Jun-03 6:49

valikac

2-Jun-03 6:49

One solution is containment. Another solution is aggregation, but only allow access to certain interfaces.

Kuphryn

Brian van der Beek2-Jun-03 21:00

2-Jun-03 21:00

Kuphryn, thanx for your answer, but could you elaborate your answer? How does containment work? Can you show me an example or article?

valikac3-Jun-03 8:06

valikac

3-Jun-03 8:06

Concept of containment is as C++'s "has a" inheritance relationship. In other words, the outside COM object containers interfaces that will then utilize the inner object. The outsider exposes whatever functions it wants.

Kuphryn

Vi23-Jun-03 2:45

Vi2

3-Jun-03 2:45

Your non-creatable object should not have the class-factory. However I don't know how to make it possible in MFC.

With best wishes,
Vita

Brian van der Beek3-Jun-03 21:33

help resolve access violation in ole32.lib

3-Jun-03 21:33

I found what I was looking for. I just have to remove the coclasses from the idl file, so the classes are not registered. This way external applications can only access the main (co-)class. Now the 'non-coclasses' cannot be created with CoCreateInstance anymore, instead they have to be created by calling their own static CreateInstance method.

EXCEL and MFC

Daniela12329-May-03 10:08

Daniela123

29-May-03 10:08

I want to export data from a MFC program to EXCEL 97.
The function prototypes are in excel8.h
This is all part of excel8.olb. The only documentation I can find is for VB (vbaxl8.hlp on the MS Office distribution CD)
WHERE CAN I FIND THE DOCUMENTATION FOR THE FUNCTIONS OF excel8.h (for C/C++ not VB)

Anybody who knows COM, and OLE Automation should know...
I am just a rookie when it comes to this part of programming

Ethernal gratitude is guaranteed...

Daniela

Re: EXCEL and MFC

Daniela1233-Jun-03 10:58

Daniela123

3-Jun-03 10:58

I have to reply to my own post...
There is NO documentation for EXCEL Automation for C++.
It is extremely difficult using the VB documentation to get the C++ code right.
For example

range.PasteSpecial(Paste, Operation, SkipBlanks, Transpose)

In VB, all 4 parameters are VARIANTS
in the C prototype file excel8.h, the first two parameters
are of type long.
The "#define" for parameter Paste can nowhere be found

I found a pathetic way to work around my problems.
Just record a bunch of macros in EXCEL and call them from the C program

myapp.Run( COleVariant("MyMacro"),...)

//there are 30!!! optional parameters instead of the periods

Daniela

Re: EXCEL and MFC

Mardigin18-Jul-03 10:11

Mardigin

18-Jul-03 10:11

I am having the same problem. Augh.

If you find any good documentation please let me know.

Mardigin

safee ullah28-May-03 23:19

safee ullah

28-May-03 23:19

hi there..

i am enabling mfc in an activex control and what happens is that when i debug it ..it throws an access violation in OLE32.lib..
dont know why..ne ideas? Smile | :)

regards
safee

Re: help resolve access violation in ole32.lib

safee ullah4-Jun-03 1:35

safee ullah

4-Jun-03 1:35

thanks amigo..
it got resolved..
i logged on today ... sorry for keeping u waiting..

regards
safee

COM+ error in evt log. 0x80070008, error comsvcs.cpp line 289...

Anonymous27-May-03 22:29

Anonymous

27-May-03 22:29

I [users] get this error when the service has run for a long time...
Any idea about this?
the event log shows..
----------------------------------------------------------------------
The COM+ Services DLL (comsvcs.dll) was unable to load because allocation of thread local storage failed.

Process Name: MyExe.exe
Error Code = 0x80070008 : Not enough storage is available to process this command.
COM+ Services Internals Information:
File: .\comsvcs.cpp, Line: 289

----------------------------------------------------------------------

After seraching in the net, I realized that I am not the only one to get this problem... There are many executables which get this error. Apparently we are all doing the same kind of process.. [like calling CoInit many times (with proper un-inits)..etc]

But, nowhere a solution is discussed... any luck here??

Thanks for your time!
Rose | [Rose]

create a activex control from a VC++ project

A.Satish Kumar27-May-03 6:00

A.Satish Kumar

27-May-03 6:00

I have done a GIS implementation in VC++ with Ms-access as back end iwant to convert this into Activex control & place it on the web .Can Anybody helpme out? Confused | :confused:

A.Satish Kumar

DCOM Server - Problem with Parameters

Anand Vinod27-May-03 3:59

Anand Vinod

27-May-03 3:59

Hi,

I've created a DCOM Server through the ATL COM Appwizard, I've added a custom (IUnknown) interface and added some methods as below;

[helpstring("method GetComputerName")] HRESULT GetComputerName([out] BSTR *pName);
[helpstring("method GetComputerTime")] HRESULT GetComputerTime([out] long *lTime);

I was able to compile and call these methods thru the client and successfully get the values even from a remote machine.

Now I added a CLIENTINFO Structure in a header file and included the file in the idl using the #import directive,

#import "ClientInfo.h"

I added another method with a pointer to the ClientInfo structure as the parameter as follows

[helpstring("method GetComputerName")] HRESULT GetComputerName([out] LPCLIENTINFO pClInfo);

I was able to compile the code, but when i call this function from the client code, i get an exception and it crashes.

I want to know if we can pass User-Defined Data structures as parameters in a DCOM server? Why is this giving a problem even though i have derived the interface thru IUnknown? Shud we use VARIANTs here, but why shud we since i havent specified an IDispatct \ Automation interface?

The same thing works fine if i create an IN_PROC DLL.

Please tell me how we can achieve this in DCOM, also pls direct me to any examples or tutorials or articles on this.

Thanks,
Anand

John M. Drescher27-May-03 4:32

John M. Drescher

27-May-03 4:32

I just went through this. DCOM will only marshall IDL types so LPCLIENTINFO will not go accross computer boundries. The short answer you need to pass the parameter as a safe array. See the following link:

http://www.codeproject.com/com/dcomstream.asp?target=ccomsafearray[^]

John

Anand Vinod27-May-03 18:40

Anand Vinod

27-May-03 18:40

Thanks John. Cant this be done if we do custom marshaling. And I have seen an RPC server which takes Struture Pointers as above as parameters in the IDL file.

Thanks
Anand

John M. Drescher28-May-03 2:46

John M. Drescher

28-May-03 2:46

Anand Vinod wrote:
Cant this be done if we do custom marshaling.

I believe it can if you do custom marshaling.

John

jduncalf27-May-03 21:47

jduncalf

27-May-03 21:47

Your [out] parameter is incorrect. A pointer-to-a-pointer must be passed in (similar to QueryInterface) :-

HRESULT GetComputerName([out] LPCLIENTINFO *pClInfo);

OR

HRESULT GetComputerName([out] CLIENTINFO **pClInfo);

Implementation :-

HRESULT GetComputerName(CLIENTINFO **pClInfo)
{
*pClInfo = new CLIENTINFO;
(*pClInfo)->m_bstrComputerName = SysAllocString(L"");

return S_OK;
}

The single level pointer that you were passing is only valid within a single process address space.