Microsoft KB Archive/263884

= Description of the AdoChng.exe sample that demonstrates how to write an Active Template Library (ATL) COM .dll file =

Article ID: 263884

Article Last Modified on 1/9/2006

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APPLIES TO


 * Microsoft ActiveX Data Objects 2.0
 * Microsoft ActiveX Data Objects 2.1
 * Microsoft ActiveX Data Objects 2.5
 * Microsoft ActiveX Data Objects 2.7
 * Microsoft Visual C++ 2005 Express Edition
 * Microsoft Visual C++ .NET 2003 Standard Edition
 * Microsoft Visual C++ .NET 2002 Standard Edition
 * Microsoft Visual C++ 6.0 Enterprise Edition
 * Microsoft Visual C++ 6.0 Professional Edition
 * Microsoft Visual C++ 6.0 Standard Edition

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This article was previously published under Q263884



Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry



Note Microsoft Visual C++ .NET 2002 and Microsoft Visual C++ .NET 2003 support both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model. The information in this article applies only to unmanaged Visual C++ code. Microsoft Visual C++ 2005 supports both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model.



SUMMARY
The AdoChng.exe sample demonstrates how you can write an Active Template Library (ATL) COM .dll file that will create a disconnected ADO recordset and return it to a client. The sample also demonstrates how you can make changes on the client, send only the changes to the server to minimize network traffic, and apply the changes to the database. The sample includes two different clients: a Visual C++ console application and a Microsoft Visual Basic (VBScript) client Web page that uses Remote Data Service (RDS) to connect to a remote server and instantiate the object.

The sample uses a Microsoft SQL Server 7.0 database to store its data. In order to use the VBScript client, you must have an Internet Information Services (IIS) server configured to use RDS in unsafe mode and Internet Explorer 5.0 or later on the client computer.



MORE INFORMATION
The following file is available for download from the Microsoft Download Center:

AdoChng.exe

Release Date: June 27, 2000

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

Overview
The sample consists of three parts, as described here.
 * The ATL COM object source code is in the main folder where the files are extracted. The COM object has three methods:
 * CreateTable - This method creates a table to be used on a SQL Server 7.0 database and populates it with sample data. In a production environment, it is not recommended that you allow clients to create database objects, but this method is provided to simplify the creation of the necessary table.
 * CreateRecordset - This method creates a disconnected ADO recordset and returns this recordset as an IDispatch** parameter to the client.
 * SendChanges - This method accepts an IDispatch* parameter, interprets it as an ADO recordset, reconnects to the database, and applies the changes included in the recordset. The method returns the number of records in the recordset to confirm how many records were sent by the client. As will be demonstrated in this section, if you set the marshaling option on the client to adMarshalModifiedOnly, only the changes will be sent by the client, and therefore the number of records will reflect the number of changes done on the client. It is necessary to call UpdateBatch on the client after you send the changes to the server object to clear the modified flag from the recordset on the client.
 * The Visual C++ client simply creates the COM object locally and calls its methods.
 * The VBScript client creates an RDS DataSpace object, creates the COM object on the remote IIS server, and calls the methods on the object. The client has several buttons that call procedures on the server:
 * Create Remote Object - Creates an RDS DataSpace object and creates the remote object on the server.
 * Create Table - Calls the CreateTable on the remote object.
 * Create Recordset - Calls the CreateRecordset on the remote object.
 * Send Changes - Calls the SendChanges method on the remote object and calls UpdateBatch on the client afterwards.
 * Next, Previous - Navigates the recordset.
 * Change - Changes the value of the current field to the value in the edit box.

How to Run the Sample
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To run the sample, you should follow these instructions completely:  Modify your SQL Server connection string in the AdoRsObject.h source file if necessary. For the purposes of this sample, it is better if your SQL Server is on the same computer as your IIS server if you will be using the VBSript client to minimize the administration steps needed to connect successfully. Compile the code to generate the COM object .dll file. Compile the Visual C++ client. Run the client code for the first time. Observe that UpdateChanges returns &quot;4&quot; for the number of modified records because the object is running in the same process space as the client. When an object is running in the same process space as the client, no marshaling is performed. Create an MTS Server Package or a COM+ Server Application. Install the COM object into this package. This will allow the object to run in a different process space. Rerun the Visual C++ client. Note that the number of records modified is equal to the number of changes made because only those records are marshaled to the COM object. The client calls UpdateBatch on the ADO recordset to clear the flag on the fields that marks them as modified. The next time SendChanges is called, only changes made after the UpdateBatch call are sent to the server. Configure your IIS server to allow RDS access in unsafe mode. You must also add a key called MarshalChanges.AdoRsObject under the key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters\ADCLaunch

to allow the object to be created for use by RDS. For more information about RDS, please see the &quot;References&quot; section of this article.</li> Open the TestPage.htm page in Internet Explorer on the client computer.</li> Change the location of your IIS server.</li> Click the Create Remote Object, Create Table, and Create Recordset buttons to get the ADO Recordset from the server and populate the edit controls.</li> Navigate the recordset and make changes to the value field. When you are done, click Send Changes to send the changes to the server.</li></ol>

(c) Microsoft Corporation 2000, All Rights Reserved. Contributions by Kamil Sykora, Microsoft Corporation.

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