COM Discussion Boards

knuttermutter3-Apr-08 0:21

3-Apr-08 0:21

I'm learning ATL so i tried to write a simple project supporting connection points.
I want to have a situation that one COM client can raise an event on other clients.
1) I've created new ATL Project. I selected 'Executable' and 'allow merging proxy/stub' options
2) I've added an ATL Simple Object with 'support Connection Points' option. I named it 'Test'
3) I've added a method
[id(1), helpstring("method InsertText")] HRESULT InsertText([in] BSTR txt);
to the ITest interface
4) I've addedn a method
[id(1), helpstring("method OnTextInserted")] HRESULT OnTextInserted([in] BSTR txt);
to the ITestEvents interface
5) I've regenerated CProxy_ITestEvents
6) I've implemented InsertText method

<br />
STDMETHODIMP CTest::InsertText(BSTR txt)<br />
{<br />
	this->Fire_OnTextInserted (txt) ;<br />
<br />
	return S_OK;<br />
}<br />

7) I've added DECLARE_CLASSFACTORY_SINGLETON(CTest) to CTest
8) I've built the project

Next i wanted to test it so i've created a WindowsForms C# Application. I've added reference to my Test component. I've put a textbox and a button on it and implemented the button click to call InsertText method with textboxvalue as a parameter.
i've created also a secon application with a listbox:

<br />
        private testLib.TestClass a;<br />
<br />
         public Form1()<br />
        {<br />
            InitializeComponent();<br />
            a = new testLib.TestClass();<br />
            a.OnTextInserted += new testLib._ITestEvents_OnTextInsertedEventHandler(this.Dn);<br />
         }<br />
<br />
        private void Dn(string b)<br />
        {<br />
            listBox1.Items.Add(b);<br />
        }<br />
<br />

I think that clicking button in first application should add items to the listbox in the second application but it doesnt work.

Moreover, I've added to the second application a button calling InsertText method so when clicking this button an event should by both raised and handled by the same client. But it still doesnt work.

And now something strange. When i start 3 or more instances of the second application (in modified form) it starts to work! Event is properly handled after the button is clicked!

What am I doing wrong? Thanks in advance for your help.

modified on Thursday, April 3, 2008 7:08 AM

Events from C# to COM dll (C++)

SteinarAa2-Apr-08 2:58

SteinarAa

2-Apr-08 2:58

Hi
I want to send some data from a C# application to a COM dll written in C++. I'm not able to figure out how to set this up. I'm a beginner on both C# and C++.
I'm trying to create a .NET library (C#) containg an event and then import this dll to the C++ app (COM dll) with #import "...\filename.tlb" ... Then I'm using CoCreateInstance and so on to instanciate this.

Does anyone know of a good and simple example that shows how to set this up with a C# application, a .NET library and a COM dll (C++)?

Maybe this is totally wrong method to solve my problem. You may have any other good solutions to this.

I have looked at several articles on the Net, but haven't found the "right" one yet...

I appreciate very much your help here.

Steinar

Re: Events from C# to COM dll (C++)

Randor 14-Apr-08 17:10

Randor

14-Apr-08 17:10

God dag Steinar,
Velkommen å codeproject! Jeg overveie ikke noen svaret din spørsmål! Hvor er livet inne Egersund?

-David Delaune

Making COM introp and calling the method from C# project

Mushtaque Nizamani30-Mar-08 6:06

Mushtaque Nizamani

30-Mar-08 6:06

Hi,
Here is the code of one of method of my COM object.

STDMETHODIMP Cmytestobj::FindWindowExWrapper(HWND hwndParent, HWND hwndChildAfter, LPCTSTR lpszClass, LPCTSTR lpszWindow, HWND* hwndRetWnd)<br />
{<br />
	AFX_MANAGE_STATE(AfxGetStaticModuleState());<br />
<br />
	HWND hRetFndWnd;<br />
	*hwndRetWnd = FindWindowEx(hwndParent, hwndChildAfter, lpszClass, lpszWindow);<br />
	return S_OK;<br />
}

First Question;
Is my code correct i.e. will it going to return wnd return by FindWindowEx.
Second Question:
I have generated an interop of that COM DLL and want to use that in my C# project, can anyone please tell me how can I use that in my C# project.
I have added the reference of interop in my project and able to create object of class Cmytestobj, but don’t know how to call that method, what should I replace for “HWND and LPCTSTR” data type in C# project.

Regards,
Mushq

DCOM security issue

tony_Udz27-Mar-08 17:46

tony_Udz

27-Mar-08 17:46

Hello,

Using the below code, i am trying to authorize user "Valid\User1" to create COM object of "TestServiceSecurity" from a remote machine.
This code is working fine that is it not throwing any kind of error but still it is not giving autorization to "User1".

Can anybody help me with this?

Thanks in advance.

*************************************************************************************************************************

BOOL bDaclPresent = FALSE;
BOOL bDaclDefaulted = FALSE;
DWORD dwError = 0;
DWORD dwSize = 0;
EXPLICIT_ACCESS ea;
PACL pacl = NULL;
PACL pNewAcl = NULL;
PSECURITY_DESCRIPTOR psd;
SC_HANDLE schManager = NULL;
SC_HANDLE schService = NULL;
SECURITY_DESCRIPTOR sd = {0};
SERVICE_STATUS_PROCESS ssp;
DWORD dwBytesNeeded;
PSID sid;

schManager = OpenSCManager(0, 0, SC_MANAGER_CONNECT);

if (schManager == NULL)
DisplayError(GetLastError(), TEXT("OpenSCManager"));

schService = OpenService(schManager , "TestServiceSecurity",SC_MANAGER_ALL_ACCESS);
if (schService == NULL)
DisplayError(GetLastError(), TEXT("OpenService"));

psd = (PSECURITY_DESCRIPTOR)HeapAlloc(GetProcessHeap(),
HEAP_ZERO_MEMORY, dwSize);

// Get the current security descriptor.
BOOL bResult = QueryServiceObjectSecurity(schService, DACL_SECURITY_INFORMATION, psd, 0, &dwSize);
if (!bResult)
{
if (GetLastError() == ERROR_INSUFFICIENT_BUFFER){
psd = (PSECURITY_DESCRIPTOR)HeapAlloc(GetProcessHeap(),
HEAP_ZERO_MEMORY, dwSize);
if (psd == NULL){
DisplayError(0, TEXT("HeapAlloc"));
// note HeapAlloc does not support GetLastError()
}

bResult = QueryServiceObjectSecurity(schService, DACL_SECURITY_INFORMATION, psd, dwSize, &dwSize);
if(!bResult)
DisplayError(GetLastError(), TEXT("QueryServiceObjectSecurity"));

}
else
DisplayError(GetLastError(), TEXT("QueryServiceObjectSecurity"));
}

// Get the DACL.
bResult = GetSecurityDescriptorDacl(psd, &bDaclPresent, &pacl, &bDaclDefaulted);
if (!bResult)
DisplayError(GetLastError(), TEXT("GetSecurityDescriptorDacl"));

// Build the ACE.
BuildExplicitAccessWithName(&ea, TEXT("Valid\\User1"), COM_RIGHTS_EXECUTE,
SET_ACCESS, NO_INHERITANCE);

dwError = SetEntriesInAcl(1, &ea, pacl, &pNewAcl);

if (dwError != ERROR_SUCCESS)
DisplayError(dwError, TEXT("SetEntriesInAcl"));

//AddAccessAllowedACEToACL(
bool bIsValidACL = IsValidAcl(pacl);

// Initialize a NEW Security Descriptor.
bResult = InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
if (!bResult)
DisplayError(GetLastError(), TEXT("InitializeSecurityDescriptor"));

// Set the new DACL in the Security Descriptor.
bResult = SetSecurityDescriptorDacl(&sd, TRUE, /*pNewAcl*/NULL, FALSE);
if (!bResult)
DisplayError(GetLastError(), TEXT("SetSecurityDescriptorDacl"));

// Set the new DACL for the service object.
bResult = SetServiceObjectSecurity(schService, DACL_SECURITY_INFORMATION, &sd);
if (!bResult)
DisplayError(GetLastError(), TEXT("SetServiceObjectSecurity"));

// Close the handles.
bResult = CloseServiceHandle(schManager);
if (!bResult)
DisplayError(GetLastError(), TEXT("CloseServiceHandle"));

bResult = CloseServiceHandle(schService);
if (!bResult)
DisplayError(GetLastError(), TEXT("CloseServiceHandle"));

// Free buffers.
LocalFree((HLOCAL)pNewAcl);
HeapFree(GetProcessHeap(), 0, (LPVOID)psd);

*************************************************************************************************************************

SetWindowPos in COM application

sheetal_0626-Mar-08 23:38

sheetal_06

26-Mar-08 23:38

Hi,

I am using

SetWindowPos(&wndTopMost,0,0,0,0,SWP_NOSIZE);

inside OnInitDialog() to place the dialog as the top most.But after that if i click on any other opened application this window is not getting minimized on to the taskbar.

This dialog is displayed through a com interface.

Please help,it is urgent.

COM Communication

HakunaMatada25-Mar-08 1:25

HakunaMatada

25-Mar-08 1:25

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.

---

Hakuna-Matata Beer | [beer]

It means no worries for the rest of your days...
It's our problem free, Philosophy
Jig | [Dance]

"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."

Re: COM Communication

Mike Dimmick30-Mar-08 12:58

Mike Dimmick

30-Mar-08 12:58

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

Re: COM Communication

HakunaMatada30-Mar-08 19:12

HakunaMatada

30-Mar-08 19:12

Thank You. Smile | :)

---

Hakuna-Matata Beer | [beer]

It means no worries for the rest of your days...
It's our problem free, Philosophy
Jig | [Dance]

BSTR variable

vc++_fragrance24-Mar-08 19:48

vc++_fragrance

24-Mar-08 19:48

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.

Re: BSTR variable

User 21559725-Mar-08 1:24

User 215597

25-Mar-08 1:24

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.

Re: BSTR variable

CPallini26-Mar-08 1:07

CPallini

26-Mar-08 1:07

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.
Smile | :)

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

C# class library

pnpfriend24-Mar-08 9:24

pnpfriend

24-Mar-08 9:24

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.

Re: C# class library

Scott Dorman25-Mar-08 15:37

Scott Dorman

25-Mar-08 15:37

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.
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Calling .NET component from VB. [modified]

SPanicker*23-Mar-08 21:38

SPanicker*

23-Mar-08 21:38

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

Re: Calling .NET component from VB.

Vi23-Apr-08 20:13

Vi2

3-Apr-08 20:13

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

How to Rreference COM object(tlb file) in VC++

Jahnson K21-Mar-08 10:05

Jahnson K

21-Mar-08 10:05

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

Re: How to Rreference COM object(tlb file) in VC++

User 21559722-Mar-08 3:02

User 215597

22-Mar-08 3:02

Use #import[^] to import TypeLibrary(.TLB file)

Sohail

modified 21-Apr-21 21:01pm.

Re: How to Rreference COM object(tlb file) in VC++

Jahnson K22-Mar-08 11:31

Jahnson K

22-Mar-08 11:31

Thanks Sohail,

Thanks for the good article.
I will implement and see.

Thanks
JK

Re: How to Rreference COM object(tlb file) in VC++

User 21559723-Mar-08 2:28

User 215597

23-Mar-08 2:28

OK. Let me know if you have further problems with this.

Cheers,

Sohail

modified 21-Apr-21 21:01pm.

Re: How to Rreference COM object(tlb file) in VC++

pnpfriend24-Mar-08 9:34

pnpfriend

24-Mar-08 9:34

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...)
}

Re: How to Rreference COM object(tlb file) in VC++

Jahnson K25-Mar-08 7:35

Jahnson K

25-Mar-08 7:35

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

Re: How to Rreference COM object(tlb file) in VC++

Jahnson K27-Mar-08 13:04

Jahnson K

27-Mar-08 13:04

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

Re: How to Rreference COM object(tlb file) in VC++

Vi23-Apr-08 20:19

Vi2

3-Apr-08 20:19

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

Re: How to Rreference COM object(tlb file) in VC++

Jahnson K7-Apr-08 8:19

Jahnson K

7-Apr-08 8:19

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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