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Although a very basic question, but can anybody tell me what COM uses internally to talk between components? Is the mode of communication same for COM and DCOM or are they different? Do they use RPC, Sockets, Pipes, etc...?
Thanks.
---
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It's our problem free, Philosophy
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"I think my response was 'What idiot dreamed this up?'" -- Mary Ann Davidson, Oracle's chief security officer, in typical blunt manner, remembering her reaction to the company's scheme to brand its databases as "unbreakable."
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If calling between code in the same process, in the same context, in the same apartment, there is no translation whatever. It's the same as making a virtual function call to another class in your own code.
If in a different COM+ context in the same apartment, it marshals the arguments to make any pointers context-relative, executes any code to set up the thread for the new context, and unmarshals arguments and calls the method. On return it again sets up the thread for the right context, remaps any pointers for the right context (to ensure correct interception occurs) and returns to the caller.
If in a different apartment, it depends on the receiving apartment. If the receiving apartment is an STA, it will have created a hidden window to receive incoming calls. The arguments are marshalled and a window message sent to that hidden window. When the receiving thread's message pump picks up the message and dispatches it to the window procedure, the window procedure makes the call. The calling thread waits (pumping messages, if an STA) until the call returns.
If the receiving apartment is an MTA, it uses RPC, but a special RPC channel called Local RPC, to get the call onto a worker thread.
If going cross-process, again it uses windows messaging to target an STA, and RPC to target an MTA.
For DCOM RPC is always used.
DoEvents: Generating unexpected recursion since 1991
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Hi
Can you please tell me...what is the wrong in the following code snippet .
BSTR abc;
abc is having some data in it.
Now I need to check whether abc is having empty string.
for that I wrote the code like this
if( abc ==L"")
AfxMessageBox("empty string");
But I receive a compilation error ;
Please help me to ressolve the issue.
Thanks in advance.
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Use SysStringLen[^] for BSTR
BSTR is not a class. If you wish to use == for comparing two BSTRs then use _bstr_t class which wraps BSTR data type
Sohail
modified 21-Apr-21 21:01pm.
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you may use
if ( wcscmp(abc,L"") == 0)
AfxMessageBox("empty string");
or, if you want to use the equality operator, choose to encapsulate the BSTR data inside a _bstr_t object.
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke
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Hi
I am creating dll using C#. I made the research and little bit confused with following:
1) does all the classes need Guid?
2) Does all the class need interface classes? or can I have just regular class without interface and Guid?
[Guid("....")]
public interface myclass_interface
{
....
}
[Guid("...."),
ClassInterface(ClassInterfaceType.None)]
public class myclass_class:myclass_interface
{
..
}
3) Can library have static function/procedures so other classes can call them directly?
4) Can I have a class, that will not be calling from COM client, without a guid?
Thank you.
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pnpfriend wrote: ) does all the classes need Guid?
No. This is only needed if you are going to access the class from COM.
pnpfriend wrote: 2) Does all the class need interface classes? or can I have just regular class without interface and Guid?
No, classes are not required to implement an interface. Interface essentially allow you to define the "contract" that the class will provide. It does nothing to ensure how that contract is implemented but only that specific methods/properties will be available.
pnpfriend wrote: Can library have static function/procedures so other classes can call them directly?
The library can't, but an individual class can have static methods and/or properties that can be called without requiring an instance of that class.
pnpfriend wrote: Can I have a class, that will not be calling from COM client, without a guid?
This is pretty much the same as question 1, just asked inversely...so yes, you can have a class that isn't called from COM without a GUID.
Scott.
—In just two days, tomorrow will be yesterday.
—Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
[ Forum Guidelines] [ Articles] [ Blog]
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I am trying to work out a simple COM/.NET interop code. In my project in VB, I have created a simple windows application to add two numbers. The functionality of adding is done through the help of a .NET DLL written in C#. I am quite confused by trying various ideas sugggested by people. Can anyone clarify this simply in a step by step fashion?
This my VB code:
Private Declare Function method Lib "C:\Documents and Settings\CSfiles\interop\interop\bin\Debug\interop.dll" Alias "interopdll" (ByVal X As Integer, ByVal X As Integer)
Private Sub Command1_Click()
Dim a As Integer
Dim obj As Object
obj = New sample ' I get a compile-time error for undefined user type here.
a = obj.method(CInt(Text1.Text), CInt(Text2.Text))
Label1.Caption = CStr(a)
End Sub
My C#(.NET DLL) Code:
using System;
using System.Runtime.InteropServices;
using System.Reflection;
[assembly: ComVisible(true)]
namespace interop
{
/// <summary>
/// Summary description for Class1.
/// </summary>
[ClassInterface(ClassInterfaceType.AutoDual)]
[GuidAttribute("6CE9C732-CD90-4042-A5F0-CF71DFAC2598")]
class sample
{
public sample()
{
}
public int c;
public void method(int a, int b)
{
c = a+b;
//return c;
}
}
}
In this I have registerd the DLL with /codebase switch while using regasm.exe too.
Regards,
Lenus.
modified on Monday, March 24, 2008 3:49 AM
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Statement "Private Declare Function method Lib..." is unwanted and should be removed.
I.1. Add typelib into VB project by menu "Project" -> "References...". Search your DLL or TLB there (something like "interop") and select it.
I.2. Create new instance with New and Set operator
Dim obj As sample
Set obj = New sample
II. Create new instance with CreateObject and Set operator
Dim obj As Object
Set obj = CreateObject("interop.sample")
With best wishes,
Vita
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Hi All,
I have generated a tlb file through idl for the implementation of COM.
I want to use this COM object in my VC++ code.
Anybody know how to reference tlb file in VC++ code.
For VB I can directly reference the tlb file, but I dont dont know is there any way we can reference tlb file in my VC++ code and start using the methods inside COM object
Thanks in Advance
JK
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Use #import[^] to import TypeLibrary(.TLB file)
Sohail
modified 21-Apr-21 21:01pm.
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Thanks Sohail,
Thanks for the good article.
I will implement and see.
Thanks
JK
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OK. Let me know if you have further problems with this.
Cheers,
Sohail
modified 21-Apr-21 21:01pm.
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You have to import the tlb file to ur VC++
I declare it in header file.
#import "C:\myDll\mydll.tlb" raw_interface_only
...
..
public Void INiComObj()
{
CoInitialize(NULL);
HRESULT hr = CocreateInstance(CLSID...)
}
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Hi Sohail,
Thanks for the good article.
And thanks to pnp for giving the sample code.
I did import my tlb file with raw_interface_only option.
#import "C:\temp\Mytlb.tlb" raw_interface_only
I am facing following compilation error in *.tlh file.
error C2504: 'AnyObject' : base class undefined
When I see my tlh file my class is deriving from AnyObject base class.
I am not sure why it is deriving from AnyObject?
Is there any base class "AnyObject" in C++? If yes what are the include files i need to include? Please help me.
Thanks in advance.
Regards
JK
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Hi All,
I found out the solution for error C2504: 'AnyObject' : base class undefined
My tlb is dependent on some other tlb so, what i did is I #import the base tlb before importing my tlb. It complies fine. There are no errors.
But, I am not able to get pointer to my COM object, when I am running following sample code
CoInitialize(NULL);
IMyComObject pObject(_uuidof(MyComObjectName));
I am getting following error in CoCreateInstance method
0x80040154 Class Not Registered
I checked the registry, there is an entry for my typelib.
I am not sure why it is not able find the class.
Any suggestions/help please..
Thanks in advance
JK
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Jahnson K wrote: I am getting following error in CoCreateInstance method
0x80040154 Class Not Registered
The TLB describes the all data of COM server, but there is no code in TLB. You should also register COM server, i.e. EXE or DLL executable module.
With best wishes,
Vita
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Thank you all,
I am able to get the COM object.
There was couple of mistates I was doing while creating CoCreateInstance.
Now it works fine.
Thanks
JK
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there are two ways
1)Use #import <typelibrary.tlb>
second you can use the class wizard and refer the tlb file, the wizard will generate the .cli and .clh file containing the wrapper around your COM component
Regards,
Sunil Tonger
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Hello friends,
I am working on CRM application that uses the 3rd party TAPI OCX(topTAPI).
All the features related to call control like call answer,call end,call
hold,call unhold works good.But the transfer and conferencing functions
of this ocx doesn't working.If anyone of you guys had used topTAPI ocx
earlier then kindly tell me the problem.I've read its documentation
properly and it doesn't allow me to initialize any of the conferencing
related functions.
OR
If anyone has the solution apart from topTAPI please let me know.
The sample code would be appreciated.
Thanks in Advance.
ritz1234
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Hi all
I'm calling IPersistFile:Save on my local machine logged in with administrator rights and I'm getting a security error any ideas would be very welcome.
I'm using VS2005 on XP SP2
Here's the code, it's basically pulled out of the VS documentation:
HRESULT CShellLink::CreateLink(LPCSTR lpszPathObj, LPCSTR lpszPathLink, LPCSTR lpszDesc, LPCSTR lpszArgs)
{
HRESULT hres;
IShellLink* psl;
::CoInitialize(NULL);
hres = CoCreateInstance(CLSID_ShellLink, NULL, CLSCTX_INPROC_SERVER,
IID_IShellLink, (LPVOID*)&psl);
if (SUCCEEDED(hres))
{
IPersistFile* ppf;
psl->SetPath(lpszPathObj);
psl->SetDescription(lpszDesc);
psl->SetArguments(lpszArgs);
hres = psl->QueryInterface(IID_IPersistFile, (LPVOID*)&ppf);
if (SUCCEEDED(hres))
{
WCHAR wsz[MAX_PATH];
if ( ! MultiByteToWideChar(CP_ACP, 0, lpszPathLink, -1, wsz, MAX_PATH)) {
DisplayLastError();
} else {
hres = ppf->Save(wsz, TRUE);
if ( ! SUCCEEDED(hres)) {
DisplayLastError();
}
}
ppf->Release();
}
psl->Release();
}
return hres;
}
Cheers
Tom
Philosophy: The art of never getting beyond the concept of life.
Religion: Morality taking credit for the work of luck.
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TClarke wrote: I'm calling IPersistFile:Save on my local machine logged in with administrator rights and I'm getting a security error any ideas would be very welcome.
I'm using VS2005 on XP SP2
Since it is a security error, I think it is important to know where you are saving to. Even as an administrator, there are parts of the system you aren't allowed to modify.
Nathan
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I'm getting the same error on W7 using VS 2008 and the same sample code. I am writing to a temp folder with security set to all access for "Everyone" from a shell running with Administrator priviledge. It still doesn't work.
Probably, as usual, MS sample code is incomplete, or not even wrong.
-Geoff
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Hello all, I know the experts on codeproject can deal with any of my sneaky questions... try this one:
What .tlb is the definition of IDataObject in?
Why do I need it: I have my own interface with IDataObject as an argument of one of its methods. The type library compiled from that .idl contains beside my own interface also IDataObject and a couple of others, which are referenced by it. As a consequence, the proxy for that interface is wrong and drag and drop stops functioning in my app  . I tried to find a type library to put in importlib("") statement, but did not find it. There must be something obvious I am overlooking.
Thanks for any advice
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