ADO 2.5 Streams and XML - 15 Nov 2001

Description: This sample demonstrates how to use the new Stream object in ADO 2.5 to read a recordset into XML and vice versa.

More Details

A Stream object provides the means to read, write, and manage the binary stream of bytes or text that comprise a file or message stream. In ADO 2.1 you can save a recordset to XML that is persisted to disk using the Save method and the adPersistXML option.
rst.Save "pubs.xml", adPersistXML

You can open a recordset based on the XML file with the Open method. rst.Open "pubs.xml"

In ADO 2.5 you can use the Stream object to work with XML without having to write it to disk first. The Stream object exists in memory. In this sample the contents of a recordset are converted to XML and then written to the Stream object, which is named 'st' here.
rs.Save st, adPersistXML

Just as a recordset can be opened from an XML file, it can also be opened based on the XML in a Stream.
rs.Open st

Setup

The sample retrieves data from the SQL Server 7.0 Northwind sample database. The connection string in the procedure btnRetrieve_Click has the following:
DataSource=(local);

If the SQL Server you are using is on a different machine you must use the name of that machine instead, for example if SQL Server is on a machine named Cocoa, you would use the following:
DataSource=Cocoa;

Browser/Platform Compatibility

This sample requires Visual Basic 6.0 and Active Data Objects (ADO) 2.5. It can be run under Windows 98, Windows NT 4.0, or Windows 2000. ADO 2.5 ships with Windows 2000 and will also be downloadable from Universal Data Access Online.
Note: This content uses a beta of ADO 2.5 and is therefore for preview only and subject to change.

Usage

The sample consists of a single form. Choose Retrieve to run a query and populate a grid with a list of products. The data resides in an ADO recordset. To apply a filter to the product list enter the filter expression and choose Apply. For example you might enter the following as a filter expression:
unitprice > 10
Only the records that meet the filter criteria appear in the grid. To remove the filter choose Clear.
To convert the contents of the ADO recordset to XML, choose ADO -> XML. The contents of the XML appear in the bottom half of the form.

To create an ADO recordset from the XML choose XML -> ADO. The contents of the recordset are displayed in the grid.