C# 4 and .NET 4

eading and Writing streamed XMl ❘ 907
}
}
richTextBox1.AppendText(rdr.Value + "\r\n");
code download XMLReaderSample.sln
As previously discussed, XmlReader is an abstract class. So in order to use the XmlReader class directly, a
Create static method has been added. The Create method returns an XmlReader object. The overload list
for the Create method contains nine entries. In the preceding example, a string that represents the filename
of the XmlDocument is passed in as a parameter. Stream-based objects and TextReader-based objects can
also be passed in.
An XmlReaderSettings object can also be used. XmlReaderSettings specifies the features of the
reader. For example, a schema can be used to validate the stream. Set the Schemas property to a valid
XmlSchemaSet object, which is a cache of XSD schemas. Then the XsdValidate property on the
XmlReaderSettings object can be set to true.
You can use several Ignore properties to control the way the reader processes certain nodes and values.
These properties include IgnoreComments, IgnoreIdentityConstraints, IgnoreInlineSchema,
IgnoreProcessingInstructions, IgnoreSchemaLocation, and IgnoreWhitespace. These properties
can be used to strip certain items from the document.
read Methods
Several ways exist to move through the document. As shown in the previous example, Read() takes you to
the next node. You can then verify whether the node has a value (HasValue()) or, as you will see shortly,
whether the node has any attributes (HasAttributes()). You can also use the ReadStartElement()
method, which verifies whether the current node is the start element and then positions you on the next
node. If you are not on the start element, an XmlException is raised. Calling this method is the same as
calling the IsStartElement() method followed by a Read() method.
ReadElementString() is similar to ReadString(), except that you can optionally pass in the name of an
element. If the next content node is not a start tag, or if the Name parameter does not match the current node
Name, an exception is raised.
Here is an example of how ReadElementString() can be used. Notice that this example uses
FileStreams, so you will need to make sure that you include the System.IO namespace via a using
statement:
private void button6_Click(object sender, EventArgs e)
{
richTextBox1.Clear();
XmlReader rdr = XmlReader.Create("books.xml");
while (!rdr.EOF)
{
//if we hit an element type, try and load it in the listbox
if (rdr.MoveToContent() == XmlNodeType.Element && rdr.Name == "title")
{
richTextBox1.AppendText(rdr.ReadElementString() + "\r\n");
}
else
{
//otherwise move on
rdr.Read();
}
}
}
code download XMLReaderSample.sln
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