Q263884: SAMPLE: AdoChng.exe Changes Business Object Via ADO Recordset
Article: Q263884
Product(s): Microsoft C Compiler
Version(s): 2.0,2.1,2.5,2.7,6.0
Operating System(s):
Keyword(s): kbfile kbSample kbADO200 kbADO210 kbDatabase kbVC kbVC600 kbGrpDSVCDB kbGrpDSMDAC kbDSu
Last Modified: 11-JUN-2002
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The information in this article applies to:
- ActiveX Data Objects (ADO), versions 2.0, 2.1, 2.5, 2.7
- Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0
- Microsoft Visual C++, 32-bit Professional Edition, version 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
Q256986 Description of the Microsoft Windows Registry
SUMMARY
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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
(http://download.microsoft.com/download/ado/SAMPLE-A/1.0/WIN98/EN-US/AdoChng.exe)
Release Date: June 27, 2000
For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:
Q119591 How to Obtain Microsoft Support Files from Online Services
Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. After it is posted, the file is housed on
secure servers that 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
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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:
1. 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.
2. Compile the code to generate the COM object .dll file.
3. Compile the Visual C++ client. Run the client code for the first time.
Observe that UpdateChanges() returns "4" 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.
4. 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.
5. 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.
6. 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 "References" section of this article.
7. Open the TestPage.htm page in Internet Explorer on the client computer.
8. Change the location of your IIS server.
9. Click the Create Remote Object, Create Table, and Create Recordset buttons to
get the ADO Recordset from the server and populate the edit controls.
10. Navigate the recordset and make changes to the value field. When you are
done, click Send Changes to send the changes to the server.
(c) Microsoft Corporation 2000, All Rights Reserved. Contributions by Kamil
Sykora, Microsoft Corporation.
REFERENCES
==========
For additional information, click the article numbers below to view the articles
in the Microsoft Knowledge Base:
Q166277 HOWTO: Create a VB Component that Returns a Recordset in RDS
Q191741 INFO: RDS Registry/Security Settings for Custom Business Objects
Q250536 HOWTO: Configure RDS for Windows 2000
Q183315 HOWTO: Write and Validate a Custom Business Object With RDS
Additional query words: AdoChng
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Keywords : kbfile kbSample kbADO200 kbADO210 kbDatabase kbVC kbVC600 kbGrpDSVCDB kbGrpDSMDAC kbDSupport kbADO250 kbATM kbado270
Technology : kbVCsearch kbAudDeveloper kbADOsearch kbADO210 kbADO200 kbADO250 kbVC600 kbVC32bitSearch kbADO270
Version : :2.0,2.1,2.5,2.7,6.0
Issue type : kbhowto
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