C# 4 and .NET 4

930 ❘ ChaPTer 33 mAnipulAtinG xml
The XmlDataDocument is based on the XmlDocument class, so it has all of the functionality that the
XmlDocument class has. One of the main differences is the overloaded constructor that the
XmlDataDocument has. Note the line of code that instantiates XmlDataDocument (doc):
doc = new XmlDataDocument(ds);
It passes in the DataSet object that you created, ds, as a parameter. This creates the XML document
from the DataSet, and you do not have to use the Load() method. In fact, if you instantiate a new
XmlDataDocument object without passing in a DataSet as the parameter, it will contain a DataSet with
the name NewDataSet that has no DataTables in the tables collection. There is also a DataSet property,
which you can set after an XmlDataDocument-based object is created.
Suppose that you add the following line of code after the DataSet.Fill() call:
ds.WriteXml("c:\\test\\sample.xml", XmlWriteMode.WriteSchema);
In this case, the following XML file, sample.xml, is produced in the folder c:\test:
HL Road Frame-Black, 58
1059.3100
HL Road Frame-Red, 58
1059.3100
Sport-100 Helmet, Red
13.0863
Only the first couple of Products elements are shown. The actual XML file would contain all of the
products in the Products table of Northwind database.
Converting relational Data
This looks simple enough for a single table, but what about relational data, such as multiple DataTables
and Relations in the DataSet It all still works the same way. Here is an example using two related tables:
private void button5_Click(object sender, EventArgs e)
{
XmlDocument doc = new XmlDocument();
DataSet ds = new DataSet("XMLProducts");
SqlConnection conn = new SqlConnection(_connectString);
www.it-ebooks.info