Calling .NET component from VB. [modified] - COM Discussion Boards

Mike Dimmick30-Mar-08 12:58

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]

"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."

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.
—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]

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

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

Member 38312474-Apr-08 3:21

Member 3831247

4-Apr-08 3:21

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

TAPI related Question

ritz123421-Mar-08 0:44

ritz1234

21-Mar-08 0:44

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. Cool | :cool:

ritz1234

Getting E_ACCESSDENIED when calling IPersistFile:Save

TClarke20-Mar-08 6:08

TClarke

20-Mar-08 6:08

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);
		// Get a pointer to the IShellLink interface. 
	hres = CoCreateInstance(CLSID_ShellLink, NULL, CLSCTX_INPROC_SERVER, 
		IID_IShellLink, (LPVOID*)&psl); 
	if (SUCCEEDED(hres)) 
	{ 
		
		IPersistFile* ppf; 

		// Set the path to the shortcut target and add the description. 
		psl->SetPath(lpszPathObj); 
		psl->SetDescription(lpszDesc); 
		psl->SetArguments(lpszArgs);

		// Query IShellLink for the IPersistFile interface for saving the 
		// shortcut in persistent storage. 
		hres = psl->QueryInterface(IID_IPersistFile, (LPVOID*)&ppf); 

		if (SUCCEEDED(hres)) 
		{ 
			WCHAR wsz[MAX_PATH]; 

			// Ensure that the string is Unicode. 
			if ( ! MultiByteToWideChar(CP_ACP, 0, lpszPathLink, -1, wsz, MAX_PATH)) {
				DisplayLastError();
			} else {

				// Save the link by calling IPersistFile::Save.
				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.

Re: Getting E_ACCESSDENIED when calling IPersistFile:Save

Nathan Holt at EMOM20-Mar-08 8:43

Nathan Holt at EMOM

20-Mar-08 8:43

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

Re: Getting E_ACCESSDENIED when calling IPersistFile:Save

Member 785300318-Apr-11 14:13

Member 7853003

18-Apr-11 14:13

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

where is the type library for IDataObject ?

Vlasta_20-Mar-08 1:05

Vlasta_

20-Mar-08 1:05

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 Frown | :(

. 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

Re: where is the type library for IDataObject ?

Nathan Holt at EMOM20-Mar-08 9:42

Nathan Holt at EMOM

20-Mar-08 9:42

Vlasta_ wrote:
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.

I can think of a couple other options. One is to provide custom marshaling for your method. Another is to just pass an IUnknown and query for IDataObject in your code. I tried to find the tlb for IDataObject and I couldn't find it either.

Nathan

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.