C / C++ / MFC

6-Aug-02 1:29

This is a simple question regarding registering a DLL that spurned from a current article about plugins:
http://www.codeproject.com/dll/PlugIn.asp

I thought that only COM DLLs needed registering with the OS. Regular DLLs
can be used as is, and registering is pointless. Am I completely wrong?

I wonder if someone would explain this to me as it has been bugging me for a while.

chin

Happy, Happy, Joy, Joy.

Tomasz Sowinski6-Aug-02 1:41

Tomasz Sowinski

6-Aug-02 1:41

Rchin wrote:
Regular DLLs can be used as is, and registering is pointless. Am I completely wrong?

You're right. I've searched the article text, and there's no mention about 'registering' the plugin dlls. Did I miss something? Smile | :)

Tomasz Sowinski -- http://www.shooltz.com

What is "scratch" and why can everything be made from it?

RChin6-Aug-02 1:50

6-Aug-02 1:50

One of the article's response thread entitled 'Registering a dll in Windows 2000' got me thinking on a tangent about registering DLLs in general.

I just wanted someone to confirm (or deny) that the registration process for DLLs is only applicable to COM components with the DLL file extension.

One of the most frequently asked question around my office when installing a piece of software is 'Have you registered this/that DLL'. I am convinced that this is not a necessary practice for regular DLL libraries.

thanx for the reply.
chin

Joel Lucsy6-Aug-02 3:05

Joel Lucsy

6-Aug-02 3:05

You are correct. Anything to do with COM typically should be registered. There are ways to deal with COM without registering, but it's more problems then it's worth.
COM files come in many flavors however: dll,ocx,exe. Actually, you could call the file anything you want. But it must export (some) the functions DllRegisterServer, DllCanUnloadNow, DllGetClassObject, DllUnregisterServer.
Regular DLL's can't be registered since they wouldn't have those functions.

Joel Lucsy (jjlucsy@ameritech.net)

RChin6-Aug-02 3:13

6-Aug-02 3:13

Thank you.
That helps.

chin

ADO exception problem

unknown soldier6-Aug-02 1:17

unknown soldier

6-Aug-02 1:17

I am writing a simple DOS applicaion that is using ADO to connect to data source. The COM libraries are initializing successfully and the connection to database by connection pointer is also established.

But when i try to run a "query" using connection pointer, the following exception is raised:

Error:800a0e81.
ErrorMessage:Unknown error 0x800A0E81.
Source:ADODB.Connection.
Description:Operation cannot be performed while connecting asynchronously..

Can any one tell me why this happens ???

Here is my code:

	_bstr_t bstrQuery("SELECT * FROM Customers");
	_variant_t vRecsAffected(0L);
	_RecordsetPtr pRecordSet;

pRecordSet = m_pConnection->Execute(bstrQuery, &vRecsAffected, adOptionUnspecified);

RChin6-Aug-02 1:36

6-Aug-02 1:36

Just a stab in the dark, but you might need to create an instance of the
Recordset object

_RecordsetPtr pRecordset = NULL;

// Create COM instance. You should also test the return code for
// this for success.
pRecordset.CreateInstance(__uuidof(Recordset));

//
// etc. etc..

chin

unknown soldier6-Aug-02 2:11

unknown soldier

6-Aug-02 2:11

Not worked

RChin6-Aug-02 4:04

6-Aug-02 4:04

Your original error message mentions something about an asyncronous connection. This may be the root of all your evils Mad | :mad:

An asyncronous ADO connection requires a lot more construction code that
your entire program may be missing.

I have done a quick test and it seems to work ok.
I've provided the console function below for you to look at.

void ConnectAndDisplay()
{
	CString strSQL;				// SQL statement string
	_variant_t vtAffected;			// 
	_variant_t vtField;			// 
		
	_ConnectionPtr pConnection = NULL;	// connection smart pointer
	_RecordsetPtr pRecordset = NULL;	// recordset smart pointer

	strSQL = "Select [Name] From [CustomerTable]";

	try
	{
		TESTHR( pConnection.CreateInstance(__uuidof(Connection)) );
		TESTHR( pRecordset.CreateInstance(__uuidof(Recordset)) );
		TESTHR( pConnection->Open( _bstr_t(_T("File \\MyConnection.udl;")), "", "", NULL ) );

		// Execute pre-prepared SQL statement
		pRecordset = pConnection->Execute((LPCTSTR)strSQL, &vtAffected,adOptionUnspecified);

		// display returned results
		while( pRecordset->ADOEOF != VARIANT_TRUE )
		{
			_variant_t vtField;
			CString strField;

			vtField = pRecordset->Fields->GetItem("Name")->Value;
			/////////////////////////////////////////
			ASSERT( vtField.vt == VT_BSTR );		// we are expecting a string!!
			////////////////////////////////////////
			strField = vtField.bstrVal;

			cout<< (LPCTSTR)strField << endl;
			pRecordset->MoveNext();
		}

		pConnection->Close();
	}
	catch(_com_error e)
	{
		CString strMessage;
		strMessage.Format("Error: %s\n", e.ErrorMessage());
		AfxMessageBox(strMessage);
	}
	return;
}

Chin