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Can two threads in the same process create separate instances of the same COM Component? I mean Thread1 will have its own COM instance and Thread2 will have its own. Do I have to create the COM Component in a special way to have the above feature?
I have an application which has several threads. Now each thread must have its own instance of the COM Component. Can anyone help?
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![Beer | [beer]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/beer.gif) Hakuna-Matada
It means no worries for the rest of your days...
It's our problem free, Philosophy
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Hello Hakuna,
>> Can two threads in the same process create separate instances of the same COM Component?
Answer : Yes, certainly.
>> Do I have to create the COM Component in a special way to have the above feature?
Answer : Just make sure that the COM Component is not a SINGLETON.
Contact me again if you need any further clarification.
Best Regards,
Bio.
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Is there any way to implement the same functionality in case of SINGLETON class?
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Hello George,
>> Is there any way to implement the same functionality in case of SINGLETON class?
I'm not sure what you mean specifically by "the same functionality". Perhaps you can elaborate on this point. However, two or more threads -can- create and use a SINGLETON COM object, even without knowing that the COM object is a singleton. Each thread will think its object is its very own when in actual fact it is shared across threads.
However, there will be a subtle internal difference which involves the apartment of the COM object and the apartment(s) of the client threads. If the COM object is an STA object, and the first thread that created it is an STA thread, then only this thread will have direct access to the object. The other threads will receive a PROXY to this COM object.
Contact me again if you need any further clarifications 
Best Regards,
Bio.
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Hi all,
I have a COM program written in VC++ (unmanaged). I got the managed code written in C#. My issue is I need to call the COM dll functions from my C# program.
Does any one have an idea how to do it? If so, please reply me with me some sample code.
Thanks
Sony
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Hi. I am a newbie.
In C, I managed to read a file which consists of a single string.
How do I pass this string to VB via an OCX?
I was thinking of creating a safearray to do it but I am not to sure how to safearray a string. I have only managed to do it for numbers.
Thanks in advance!
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No need to use a SafeArray.
If the string is using ANSI, convert it to UNICODE using MultibyteToWideChar API.
For the Unicode string, call SysAllocString to make it a "good" BSTR, which is the "VB-native" string type.
Depending on the parameter declaration, you need to SysFreeString the BSTR when you are done.
Some of us walk the memory lane, others plummet into a rabbit hole
Tree<t> in C# || Fold With Us! || sighist
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Hi all,
Im new to ATL COM programming(2 weeks!). im using an api in my component.
unfortunately i havnt been able to load it appropriately(atleast this is what
the client says!). this is how i've done it... pls tell where im wrong.
i created an ATL class in the dll and added the following to the class' cpp
file in the global area
<br />
HINSTANCE hDll=LoadLibrary("API.dll");<br />
typedef short (*Init_type)();<br />
typedef short (*Close_type)();<br />
typedef short (*SetAnalog_type)(int,double);<br />
typedef short (*SetOutput_type)(int);<br />
typedef short (*ResetOutput_type)(int);<br />
typedef short (*IsInput_type)(int);<br />
<br />
Init_type Init;<br />
Close_type Close;<br />
SetAnalog_type SetAnalog;<br />
SetOutput_type SetOutput;<br />
ResetOutput_type ResetOutput;<br />
IsInput_type IsInput;<br />
<br />
Class::Class()
{<br />
Init = (Init_type)GetProcAddress(hDll,"Init");<br />
Close =(Close_type)GetProcAddress(hDll,"Close");<br />
SetAnalog = (SetAnalog_type)GetProcAddress(hDll,"SetAnalog");<br />
SetOutput = (SetOutput_type)GetProcAddress(hDll,"SetOutput");<br />
ResetOutput = (ResetOutput_type)GetProcAddress(hDll,"ResetOutput");<br />
IsInput = (IsInput_type)GetProcAddress(hDll,"IsInput");<br />
}<br />
after this i've created other methods in the class where i use these api
functions.
the dll compiles without problems, but when i use these methods in a vb
client i get this error...
The instruction at "0x00000000" referenced memeory at "0x00000000". The
memmory could not be "read".
Click on OK to terminate the program...
pls help... maybe i dont know how to load an api...im new to this. can
somebody give a link to a sample code where the coder has loaded the api and
used the functions.
Thanks in advance
Nikhil
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I am writing windowless activex control with ATL. i want this control to blink with certain rate.
I am using all the techniks ( bitmap drawing, flickerfree activation ... ) but I still see some flicking. When I use windowed activation everighing is fine. For blinkking I am using timer funcion
Can somebody dive me some idea how to fix the problem
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Hi,
I am a newbie and was not sure about the category under which my question comes. Therefore please move it to appropriate category if you guys feel so.
I have an address book application which I want to integrate with outlook/outlook express.
Can someone please tell me how can I do it ? Some tutorial or link.
My application is in some way similar to plaxo.
Thanks a lot
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Hi all,
I have trouble with a vc dll com which im using in a vb client...
i've imported a third party ocx and a dll which consists of API functions
(basically its architecture is similar to kernel32.dll) in my vc com dll and
ive used them in other classes.
i wrote a class called myerrorhandling in which has a public method
error_logger
this is the method
<br />
STDMETHODIMP errorhandling::error_logger()<br />
{<br />
FILE *fptr;<br />
char error[10]={"ERROR***"};<br />
fptr=fopen("C:\\Debug.txt","a+");<br />
fprintf(fptr,error);<br />
fclose(fptr);<br />
return S_OK;<br />
}<br />
i get this error when i create an object of the errorhandling class in vb
<br />
Run-time error '-2147024770 (8007007e)':<br />
<br />
Automation error<br />
The specified module could not be found.<br />
infact i get this error while creating an object of any class in the dll
i havnt used any api functions or thirdparty dll objects anywhere in this
class(error handling)...
i created another com dll in vc and added this errorhandling class and it
worked fine.
what could the problem be?
thanks in advance
Nikhil
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got it.. i havent been able to import the api properly.
how do i import kernel32.dll in my com dll if i wanna use gettickcount??
pls help
thnks
nikhil
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I think you can use the LoadLibrary and make a call to GetTickCount function using the GetProcAddress
Somethings seem HARD to do, until we know how to do them.
 _AnShUmAn_
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Hello,
I am using MFC - ActiveX control in C# based windows application.
I am not able to debug the control with the C# application while it is possible with the MFC applcation.
Is it possible to do so if yes then HOW.
Thanks.
Byee..
Gajesh
Pune(India
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Is that DCOM is implemented through Microsoft Transaction Server. If not so then how it is implemented.
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DCOM stands for Distributed COM, and refers to the ability to call COM objects running on another machine. DCOM is implemented over DCE-compatible Remote Procedure Calls [RPCs]. CoCreateInstance calls from the client are translated into a message that's sent over the network, which is received by the server computer's RPC subsystem, the RpcSs service. In modern versions of Windows, this service runs in a SvcHost.exe process. The RPC subsystem locates a process to serve that class, starting one if necessary, and calls the process on the client's behalf. I'm not sure if the system then hands the network connection over to the server process so that future calls don't have to go through the RPC subsystem. The exact network protocol used, below the RPC protocol, is dependent on the configuration and on which network protocols the system has installed. On Windows XP and Server 2003 machines, only connection-oriented protocols such as TCP are enabled by default; earlier versions could use UDP if the call security didn't require a connection.
MS Transaction Server was a way of setting up different contexts for objects, to allow them to interact without knowing about one another. It offered transaction support, object pooling and just-in-time activation. You had to program a little differently for MTS than for COM. In Windows 2000, MTS was incorporated into the regular COM APIs and was renamed COM+. With MTS and COM+, it's possible to have a COM component implemented as a DLL but still run outside the creating process, using a surrogate process (dllhost.exe). To communicate between processes running on the same system, COM uses a special form of RPC called Local RPC.
DCOM predates MTS by a couple of years.
Stability. What an interesting concept. -- Chris Maunder
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Hello world!!!
I created a UPnP device which works as a control point. It succeeded but now I'm facing a great problem. I'm trying to register the device with the host in order to be published on the network. But the IUPnPRegistrar::RegisterRunningDevice method doesn't work. The return value of this is an E_FAIL which is a non-specified error value. Thus I think the DLL in which I wrote the device control object is bad. So I need a help from anyone who have already registered a UPnP device or anyone who know very well how to process.
Thanks for the help.
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My ActiveX project has some problem, It's Can't Add Method and Property. It's hint Error adding a(n) method to the associated class.I'm use vc6+sp6.
tell me why ,thank you.
msn:Flashcutreg@hotmail.com
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* Make sure all relevant files are not read-only
* close VC6, delete the .ncb and .clw (if any), then try again
Some of us walk the memory lane, others plummet into a rabbit hole
Tree<t> in C# || Fold With Us! || sighist
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Hi,
I want to add content to a view derived from MFC's CHtmlView from a thread.
The following code is a stripped back version of the code executed by the
thread.
CMyHTMLView::AddHTML()
{
HRESULT hr = CoInitialize( NULL );
ASSERT( SUCCEEDED( hr ) );
string shtml( "Hello World" );
try
{
CComQIPtr< IHTMLDocument2 > pHtmlDoc( GetHtmlDocument() );
if ( pHtmlDoc )
{
CComQIPtr< IHTMLElement > pBodyElement;
HRESULT hr = pHtmlDoc->get_body( &pBodyElement );
if ( SUCCEEDED( hr ) )
hr = pBodyElement->insertAdjacentHTML( _bstr_t(L"beforeEnd"), _bstr_t( shtml.c_str() ) );
ASSERT( SUCCEEDED( hr ) );
}
}
catch( _com_error e )
{
REPORT_COM_ERROR(e);
}
catch(...)
{
}
CoUninitialize();
}
If the contents of shtml is small as shown above it works fine. However when
shtml is a few K of HTML the call to insertAdjacentHTML() throws an
exception which is caught in catch(...). The HTML is valid and the same code
works fine when it isn't in a thread. In the real code, shtml is on the
heap or maybe the stack?
Any clues about what I'm doing wrong?
Neville Franks, Author of Surfulater www.surfulater.com "Save what you Surf" and ED for Windows www.getsoft.com
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It could be something to do with thread-local data, a lot of MFC uses it. I've had problems trying to manipulate objects from threads - usually you have to do the work in the thread that created the object, but presumably this takes away the point of what you're trying to do.
It won't matter if shtml is on the stack or heap, but you should check if insertAdjacentHTML completes when the function returns or maybe it takes the data, returns and then some other thread processes it. Some of the html stuff has other threads to do work. Have you tried putting a sleep in after the insert to give it time to complete?
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Hi Keith,
Thanks for the reply. I got the following reply on an MS Newgroup, which explains things.
You cannot simply pass COM interface pointers to a worker thread - you
need to marshal them. See
http://support.microsoft.com/?kbid=150777
MSHTML is a single-threaded component. If you don't marshal the
pointers - in violation of COM rules - you'll likely get random crashes.
If you do marshal, then any call you make in the worker thread though
such a pointer gets marshalled back to the main thread, executed there,
and any results marshalled back to the worker. Essentially, the worker
thread isn't doing any work, it spends all its time waiting for the main
thread to serve its calls.
Bottom line: it's pointless to perform DHTML manipulations from a worker
thread. You add pure overhead, without gaining anything at all.
I was already working on implementation that built the HTML in a thead and
added it to a queue for the app thread to display. My main problem was
getting the main thread to be a bit more responsive when large chunks of
HTML are in play. After a few different implementations, I've now got
something I'm quite happy with.
Neville Franks, Author of Surfulater www.surfulater.com "Save what you Surf" and ED for Windows www.getsoft.com
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If you are using the use the interfaces in a different thread than the one creating the control, you need to marshal it to this thread (CoMarshalInterThreadInterfaceInStream and CoGetInterfaceAndReleaseStream, which probably were made to win the WIN 32 API lyrics award)
chopping strings usually isn't a symptom of violating apartment boundaries, but MSHTML ctrl has a few message loop interacitons that make that possible.
Some of us walk the memory lane, others plummet into a rabbit hole
Tree<t> in C# || Fold With Us! || sighist
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I'm trying to register a dll on a Win2003 server, but an getting the message "DllRegisterServer in ...filename... failed. Return code was 0x8007007e". This error supposedly means a module is missing. I think all the DLLs are there - it's a standard atl dll.
I can register the dll fine on my development pc and on another Win2003 server, just this one I can't. I tried loading up the registry entries manual, but I just get an error when I try to use createobject.
Any ideas why I can do it on one server and not another?
Thanks
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