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I have some APIs that take one or more struct as input parameters. I need to call these APIs remotely (from a different computer than the one they are sitting on).
I figured I could use DCOM. However, how do I call a COM object with a struct as the input?
THanks
merlinos
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You can define structs in MIDL which you can pass over DCOM. The good way to pass the structs to your API would be to repackage the struct in your COM methods. The ugly way would be to just cast and pass the structs to the API functions. Good method
HRESULT COMClass::Method(Struct* pPassedIn)
{
APIStruct s;
s.field = pPassedIn->field;
APICall(&s);
return S_OK;
}The ugly way
HRESULT COMClass::Method(Struct* pPassedIn)
{
APICall((APIStruct*)pPassedIn);
return S_OK;
}For the latter case, just make sure the MIDL-struct members are packed and aligned as the API struct.
--
Wir müssen leben bis wir sterben.
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Could you please explain in more details what do you mean? I'm not very familiar with all COM/DCOM abbreviations,even thow I have a basic knowledge on the topic, so could you please explain what is APIStruct,APICall and how is it related to MIDL ?
Thanks
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APIStruct and APICall are just fictious names for the functions he wants to call using DCOM. It is not related to MIDL at all. However, his COM-methods could forward the calls to these APIs, which was the point with my previous message.
--
Wir müssen leben bis wir sterben.
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Hello,
my Win2k MFC dialog application exports data to en excell file by using Automation (excel9.olb type library) and works fine if the function doing this is placed in an OnButton() function of the dialog class. Unfortunately, when I put it in a thread it always fails with the message: "Microsoft Visual C++ Runtime Library Runtime Error! abnormal program termination". I need to put the function in a thread since it takes a while to complete its task and I don't want the main window to freeze in the meantime. Does anybody know where the problem might lie? And what is this Runtime Library anyway? I've heard the word "runtime" many times but never actually knew what it exactly meant.
thanx for your answers
Koxin
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koxin wrote:
my Win2k MFC dialog application exports data to en excell file by using Automation (excel9.olb type library) and works fine if the function doing this is placed in an OnButton() function of the dialog class. Unfortunately, when I put it in a thread it always fails with the message: "Microsoft Visual C++ Runtime Library Runtime Error! abnormal program termination". I need to put the function in a thread since it takes a while to complete its task and I don't want the main window to freeze in the meantime. Does anybody know where the problem might lie?
To use automation from a background thread, the thread needs to call CoInitialize or OleInitialize, and of course the appropriate uninitialize function before it exits. Could that be the problem?
Nathan Holt
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I've been developing an IDL-like programming language and wrote a system of complex namespaces that cover most of core features (everything from garbage collecting to automatic serialization, dynamic casting ...). I'd like to ask how many of you feel this is a good thing to do and how many that it's a bad thing?
Software developer
MA, USA
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Hi, and then why?!!!!
I mean why have you decided to build such a thing?
while there are enough much better programming languages available?!!
Don't you think it's kind of wasting your time?
Any way, that's a good programming practice.
but not convinient for starting to program with such new language.
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MohammadAmiry wrote:
while there are enough much better programming languages available?!!
Don't you think it's kind of wasting your time?
Uh, excuse me. How do you know there are better languages available, when you haven't even seen his? He might be sitting on the next programming revolution, and here you are acting like an old Fortran programmer. 
--
Wir müssen leben bis wir sterben.
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OK, I haven't seen his programming language.
Neighther I ment to disappoint him.
Anyway I myself would like very much to see this new programming language.
And who knows? After that I might change my idea!;)
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Hello,
I use the (vbscript.dll) IRegExp COM for regular expressions (info got from this article (http://www.codeproject.com/string/use_regular_expression_in_your_program.asp[^]
in my c++ program, it seems to work ok, but some of the paramters won't work.
Check this out
<br />
static IRegExpPtr regExp; <br />
<br />
regExp.CreateInstance( __uuidof(RegExp) );<br />
<br />
CString mystr = _T("<something>what<something>else>");<br />
CComBSTR bst(mystr);<br />
<br />
regExp->put_Pattern( bstr_t( "<something>" ) );<br />
<br />
_variant_t v;<br />
VariantInit(&v );<br />
v.boolVal = TRUE;<br />
<br />
regExp->put_Global( v.boolVal );
regExp->get_Global( &v.boolVal );
<br />
It just fails to set the global parameter to true.
If anyone has used the IRegExp interface before and knows about this problem,
please help.
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necroleak wrote:
v.boolVal = TRUE;
I don't know if this will solve your problems, but VARIANT_BOOLs use the values VARIANT_TRUE and VARIANT_FALSE. I always convert back and forth between BOOL, bool <-> VARIANT_BOOL, in case some code tests against VARIANT_TRUE. VARIANT_FALSE is 0, as is FALSE, as well as false when it's evaluated as an integer.
For instance, IIRC, TRUE is defined as 1, while VARIANT_TRUE is defined as (unsigned int)-1 = 0xFFFFFFFF. Thus TRUE == VARIANT_TRUE is indeed false.
--
Wir müssen leben bis wir sterben.
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My client who is using our library written in COM, need to use multi-threads to access our library. However, he needs to call AfxOleInit() in his application.
Is there any way around this?
I have tried calling CoInitializeEx in worker threads (and the main thread calls AfxOleInit() ), but it doesn't work. The worker threads couldn't access our library as the COM apartment is single thread even through he specified COINIT_MULTITHREADED for the 2nd parameter of CoInitializeEx() call.
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CBasicNet wrote:
The worker threads couldn't access our library as the COM apartment is single thread even through he specified COINIT_MULTITHREADED for the 2nd parameter of CoInitializeEx() call.
What exactly do you mean with "access our library"? If you are trying to access an interface pointer, created in one apartment, from another apartment, everything will fail. You must first marshal the interface pointer to the apartment where you want to use it. Please see this article[^].
--
Wir müssen leben bis wir sterben.
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Hi!
I implement IOleCommandTarget in a .net COM server.
Here's my code. I'm trying to implement an object that can be used as a
COM object for a button in IE. I get a System.ExecutionEngineException when hitting the button (.
---------------------------------implement------------------------------------------
// Import IOleCommandTarget interface
[StructLayout(LayoutKind.Sequential,CharSet=CharSet.Unicode)]
public struct OLECMDTEXT
{
public uint cmdtextf;
public uint cwActual;
public uint cwBuf;
[MarshalAs(UnmanagedType.ByValTStr,SizeConst=100)]public char rgwz;
}
[StructLayout(LayoutKind.Sequential)]
public struct OLECMD
{
public uint cmdID;
public uint cmdf;
}
// Interop definition for IOleCommandTarget.
[ComImport,
Guid("b722bccb-4e68-101b-a2bc-00aa00404770"),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IOleCommandTarget
{
void QueryStatus(ref Guid pguidCmdGroup, UInt32 cCmds,
[MarshalAs(UnmanagedType.LPArray, SizeParamIndex=1)] OLECMD[] prgCmds, ref OLECMDTEXT CmdText);
void Exec(ref Guid pguidCmdGroup, uint nCmdId, uint nCmdExecOpt, ref object pvaIn, ref object pvaOut);
}
-----------------------------------implement----------------------------------------
-----------------------------------using----------------------------------------
[ClassInterfaceAttribute(ClassInterfaceType.None)]
[GuidAttribute("81AC67A9-1511-4104-93AC-BD8BFEC93F71")]
[ProgIdAttribute("MyDll.dll")]
public class GetURL: IObjectWithSite, IOleCommandTarget
{
protected SHDocVw.IWebBrowser2
m_pIWebBrowser2; // the browser class object
public GetURL()
{
}
public void SetSite(object pUnkSite)
{
// MessageBox.Show("SetSite");
if (m_pIWebBrowser2!=null)
Release();
if (pUnkSite==null)
return;
IServiceProvider isp = (IServiceProvider)pUnkSite;
try
{
//!!!!!получаем указатель на SHDocVw.IWebBrowser2 через IServiceProvider а не QueryInterface
Guid g1 = typeof(SHDocVw.IWebBrowserApp).GUID;
Guid g2 = typeof(SHDocVw.IWebBrowser2).GUID;
object obj;
//isp.RemoteQueryService( ref g1, ref g2, out m_pIWebBrowser2 );
isp.QueryService( ref g1, ref g2, out obj );
//получили объект и преобразуем его к SHDocVw.IWebBrowser2
m_pIWebBrowser2 = (SHDocVw.IWebBrowser2)obj;
}
catch(System.Runtime.InteropServices.COMException ex)
{
//
}
MessageBox.Show(m_pIWebBrowser2.ToString());
}
public void GetSite(ref System.Guid riid, out object ppvSite)
{
ppvSite = m_pIWebBrowser2;
try
{
//
}
catch(Exception ex)
{
MessageBox.Show(ex.Message + " GetSite");
}
}
public void QueryStatus(ref Guid pguidCmdGroup, UInt32 cCmds, OLECMD[] prgCmds, ref OLECMDTEXT CmdText)
{
MessageBox.Show ("Query status");
}
public void Exec(ref Guid pguidCmdGroup, uint nCmdId, uint nCmdExecOpt, ref object pvaIn, ref object pvaOut)
{
MessageBox.Show ("Execing");
}
}
-----------------------------------using----------------------------------------
In what a mistake? Help! Plz!!
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Hi,
I’ve got a strange behaviour of DCOM on Windows 2003 Server. I’ve created COM-server (out-of-process) and COM-client for that COM-server. Both work successfully on local computer under any operation system. Also server and client work fine when COM-server is installed on Windows 2003 Server and when COM-client works on other PC running Windows XP.
When I try run COM-server on Windows XP and COM-client on Windows 2003 Server, COM-client told me “Can’t query COM-server at remote PC: Permission denied”.
Windows XP and Windows 2003 Server are located at the same network and at the same workgroup (not used domains). All permissions are set by default.
What should I do? Here is the sample code of COM-client:
CoInitializeEx(NULL,COINIT_MULTITHREADED);
IReqAuth * pReqAuth;
WCHAR *wszMachineName=L"ALPHA\0";
COSERVERINFO srv;
ZeroMemory(&srv,sizeof(srv));
srv.pwszName=wszMachineName;
MULTI_QI qi;
qi.pIID=&IID_IReqAuth;
qi.hr=0;
qi.pItf=NULL;
HRESULT hr=CoCreateInstanceEx(CLSID_ReqAuth,
NULL,
CLSCTX_SERVER,
&srv,
1,
&qi);
if (SUCCEEDED(hr))
{
pReqAuth=(IReqAuth *)qi.pItf;
printf("COM object OK\n");
char szTmp[MAX_PATH];
BSTR AppVersion;
hr=pReqAuth->GetVersion(&AppVersion);
if (SUCCEEDED(hr))
{
memset(szTmp,0,sizeof(szTmp));
wcstombs(szTmp,AppVersion,SysStringLen(AppVersion));
printf("AppVersion: %s\n",szTmp);
SysFreeString(AppVersion);
}
else
{
sprintf(szTmp, "GetVersion failed hr = %x\n", hr);
printf(szTmp);
};
pReqAuth->Release();
}
else
{
printf("Error creating COM-object %d\n",GetLastError());
};
::CoUninitialize();
Sleep(200);
Please help, my brains can’t think anymore.
Sincerely Yours,
RadioShark
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juz go thru the links below..
1[^]
2[^]
rgds..mil10
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I am a newbee on .Net C++. Just bought it.
Reading the book. Read the (short) chapter
on COM. Basically it said, one can keep ones
COM code. My question... Is there a BETTER
way in .Net?
I have a application with COM supplied solutions
to common user needs.
As I am moving to .Net -- I have the opportunity
to provide those solutions through .Net rather
than via COM servers.
A recommendation of where to read would be
appreciated.
WedgeSoft
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Good Question. My impression is that .NET took the best concepts that COM developed and incorporated them into it's internal structure. There are profound differences, though. In his book, ".NET and COM: The Complete Interoperability Guide", Adam Nathan describes the .NET Framework as an evolution of COM. I recommend you read that book, it thoroughly describes writing code that understands how to interoperate in both the 'COM world' and the '.NET world'. The engineers at Microsoft put alot of work into making COM type libraries operate in managed applications as if they were .NET components.
There are some HUGE differences, though. You'll notice immediately that the types are considerably different, and marshaling data between two disparate types is difficult. The .NET compiler includes some excellent utilities to help the developer with COM interop. Check out the The OLE/Object Viewer, the Type Library Importer (TypImp.exe) and the IL Disassembler.
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need to know some COM stuff, can someone kindly recommend a good/popular COM/COM+ book?
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I got a good deal out of Developers's Workshop to
COM and ATL 3.0 by Andrew W. Troelsen. I knew
nothing about COM -- read the book and did the
exercises. Now my project has COM support.
(This is a beginners COM book; but not for
beginner C++ programmers.)
Modified:
(And read the reply to my question about a
.Net alternative to COM -- there Zeta makes
a recommendation to me.)
WedgeSoft
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One of the principal references for COM is: "Essential COM", by Don Box, published in 1998. He writes for the C++ developer (all the code examples are C++). But, he explains everything clearly and thoroughly. Retails for $45.
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I wrote a COM Server using ATL wizard, so i made a DLL, and want to use it on another machine - but, when i try to register my server using regsvr32 i have next message:
"LoadLibrary("the way to my dll") failed. The specified module could not be found".
Where the problem is???
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Simply it tries to say, that some library your dll depends on is missing. I would suspect, that you built your dll with dependency on msvcrt libraries that are supplied with VC.
You can either redistribute the dlls or you can build it with no dependency using static linking - see project settings of your project.
Anyway, you can check the dependency with the depends tool from the SDK.
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Yes, i built my programm with static linking method. And i noticed one thing, if Visual Studio and Active Sync installed on machine, my dll registers successfully, but if one of theme is apsent it writes an error. I tried to use dependecy utility, found all the dlls and copied them with my COM dll on another machine, and still have error.
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