Synchronizing Data
Take a look at the following code snippet:
AngusHardware dataSet = new AngusHardware( ); XmlDataDocument doc = new XmlDataDocument(dataSet); doc.Load("HierarchicalCoupons.xml"); XmlTextWriter writer = new XmlTextWriter(Console.Out); writer.Formatting = Formatting.Indented; dataSet.WriteXml(writer);
You’ve already seen code that uses this pattern It
creates an instance of a DataSet
, specifically the
one we generated for the Angus Hardware coupon database. Then it
loads the DataSet
with data from an XML file by
creating an XmlDataDocument
for it. When the data
is written to the console, it appears in a relational XML format.
But if you change the last line, as shown below, you get hierarchical
XML output that matches the format and content of the document you
loaded into the XmlDataDocument
:
doc.WriteTo(writer);
The
XmlDataDocument
knows how to map between the
relational form of the DataSet
and the
hierarchical form of the document it’s been loaded
with, as long as the element names are the same. In fact, it handily
ignores any elements it’s not familiar with from the
schema in the DataSet
when it writes the
relational XML.
This is handy because you can read in XML from the hierarchical
format and edit it using the DataSet
, then output
it back into the hierarchical XML. In other words, you can accomplish
all the work this lengthy bit of DOM code does:
dataSet.EnforceConstraints = false; XmlElement coupons = doc.CreateElement("coupons"); doc.DocumentElement.AppendChild(coupons); ...
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