I said the generated schema is a normal XML Schema document, and it is. It does, however, contain a few extra attributes with the msdata prefix. These attributes help the XSD tool to generate a subclass of DataSet with convenience methods to access tables and columns in a more type-safe manner. After running the CreateDataSet program, execute this command:

xsd /dataset Coupons.xsd

The resulting file, Coupons.cs, contains the class AngusHardware, which extends DataSet, as well as a number of support classes. It’s a much more complex structure than the one we generated in Chapter 8 and Chapter 9, and with good reason; it is used to create a DataSet, not just to load XML data with XmlSerializer.

You can see the benefit of the generated DataSet if you compare the code in Example 11-5 with that in Example 11-7.

using System;

public class CreateData {
  public static void Main(string [ ] args) {

    AngusHardware dataSet = new AngusHardware( );

    dataSet.coupons.AddcouponsRow(
      "763FF", 0.5, (int)DiscountType.Fixed, new DateTime(2002,12,31));

    dataSet.WriteXml("Coupons.xml");
  }
}

The generated DataSet class contains members named after the tables and columns in the schema. To start with, the name of the main class, AngusHardware, reflects the name of the DataSet. Each DataTable of the DataSet is represented by a generated private class within the DataSet; the “coupons” table, for example, is represented by the generated class AngusHardware.couponsDataTable. The AngusHardware.coupons property provides direct access to the “coupons” DataTable instance. The AngusHardware.couponsDataTable class has a method called AddcouponsRow( ), whose parameters match the columns of the table in the order in which they were added.

The object model for the generated AngusHardware Dataset is represented by Figure 11-3.

Figure 11-3. Generated DataSet object model