C# 4 and .NET 4

eading and Writing streamed XMl ❘ 911
settings.ValidationType = ValidationType.Schema;
settings.ValidationEventHandler +=
new System.Xml.Schema.ValidationEventHandler(settings_ValidationEventHandler);
XmlReader rdr = XmlReader.Create("books.xml", settings);
while (rdr.Read())
{
if (rdr.NodeType == XmlNodeType.Text)
richTextBox1.AppendText(rdr.Value + "\r\n");
}
}
code download XMLReaderSample.sln
After the XmlReaderSettings object setting is created, the schema books.xsd is added to the
XmlSchemaSet object. The Add method for XmlSchemaSet has four overloads. One takes an XmlSchema
object. The XmlSchema object can be used to create a schema on the fly, without having to create the schema
file on disk. Another overload takes another XmlSchemaSet object as a parameter. Another takes two
string values: the first is the target namespace and the other is the URL for the XSD document. If the target
namespace parameter is null, the targetNamespace of the schema will be used. The last overload takes
the targetNamespace as the first parameter as well, but it uses an XmlReader-based object to read in the
schema. The XmlSchemaSet preprocesses the schema before the document to be validated is processed.
After the schema is referenced, the XsdValidate property is set to one of the ValidationType enumeration
values. These valid values are DTD, Schema, or None. If the value selected is set to None, then no validation
will occur.
Because the XmlReader object is being used, if there is a validation problem with the document, it will
not be found until that attribute or element is read by the reader. When the validation failure does
occur, an XmlSchemaValidationException is raised. This exception can be handled in a catch block;
however, handling exceptions can make controlling the flow of the data difficult. To help with this, a
ValidationEvent is available in the XmlReaderSettings class. This way, the validation failure can be
handled without your having to use exception handling. The event is also raised by validation warnings,
which do not raise an exception. The ValidationEvent passes in a ValidationEventArgs object that
contains a Severity property. This property determines whether the event was raised by an error or a
warning. If the event was raised by an error, the exception that caused the event to be raised is passed in as
well. There is also a message property. In the example, the message is displayed in a MessageBox.
using the XmlWriter Class
The XmlWriter class allows you write XML to a stream, a file, a StringBuilder, a TextWriter, or
another XmlWriter object. Like XmlTextReader, it does so in a forward-only, noncached manner.
XmlWriter is highly configurable, allowing you to specify such things as whether or not to indent content,
the amount to indent, what quote character to use in attribute values, and whether namespaces are
supported. Like the XmlReader, this configuration is done using an XmlWriterSettings object.
Here’s a simple example that shows how the XmlTextWriter class can be used:
private void button9_Click(object sender, EventArgs e)
{
XmlWriterSettings settings = new XmlWriterSettings();
settings.Indent = true;
settings.NewLineOnAttributes = true;
XmlWriter writer = XmlWriter.Create("newbook.xml", settings);
writer.WriteStartDocument();
//Start creating elements and attributes
writer.WriteStartElement("book");
writer.WriteAttributeString("genre", "Mystery");
writer.WriteAttributeString("publicationdate", "2001");
writer.WriteAttributeString("ISBN", "123456789");
www.it-ebooks.info