.NET & XML

Reading Data Into a DOM Tree

There’s another way to read XML directly from a database. The XmlDataDocument, which extends XmlDocument, presents the contents of a DataSet as an XML document. At that point, the data can be treated just like any other XmlDocument, including navigating to specific nodes with XPath, writing it to any sort of Stream, transforming it with XSLT, and in fact any of the other techniques I’ve shown you in this book. Example 11-11 shows a program that executes the same query from example 11-10 and writes the resulting XML to the console.

Example 11-11. Reading data as XML using XmlDataDocument

using System;
using System.Data;
using System.Data.SqlClient;
using System.Xml;

public class ReadDataAsXml {
  public static void Main(string [ ] args) {
    
    DataSet dataSet = new DataSet("AngusHardware");
    
    SqlConnection connection = new SqlConnection(
      "Initial Catalog=AngusHardware; User ID=sa");
    
    string command = "SELECT name, redemption_date, total_discount " +
      "FROM coupon_redemptions a, customers b " +
      "WHERE a.customer_id = b.customer_id";
    SqlDataAdapter adapter = new SqlDataAdapter(command, connection);
    
    adapter.Fill(dataSet, "CouponsRedeemed");

    XmlDataDocument doc = new XmlDataDocument(dataSet);   

    XmlTextWriter writer = new XmlTextWriter(Console.Out);
    writer.Formatting = Formatting.Indented;
    doc.WriteTo(writer);
  }
}

You’ve seen most of this before, but here’s a quick look at some of the more important steps. First, you create the DataSet, the SqlConnection, a SQL select command, ...