XAML 2009 Features: Node Loop flexibility
[This is part of a series on New WPF\XAML Features]
So by now most of you must have noticed the System.Xaml dll as part of your .NET 4 WPF projects. It’s a well componentized XAML stack that provides a lot of flexibility working with XAML. So at the core we a System.Xaml.XamlReader and XamlWriter which provide the base implementation and definition for a reader and writer. XamlXmlReader is a reader that reads in XAML and produces a XAML node stream. This stream is then consumed by a
XamlXmlWriter XamlObjectWriter to produce the object graph. Similarly for the Save path, you have the XamlObjectReader and XamlXmlWriter.
So the Load Path looks like
XAML à XXR à Node Stream à XOW à Object Graph
The Save path would look like
Object Graph à XOR à Node Stream à XXW à XAML
Prior to .NET 4, you didn’t have access to the internals; the access points were XamlReader.Load and XamlWriter.Save in PresentationFramework. In .NET 4, we provide access to the node stream and you could manipulate this node loop. There are 7 XamlNodeType’s that you need to look out for in this node loop.
An example of a node loop could be filtering out events and unknown elements. Wouldn’t that make a nice feature in XamlPadX J..
The code below shows how we could replace the Window in the Xaml passed with a Page.
XmlReader xmlReader = XmlReader.Create(input);
XamlXmlReader reader = new XamlXmlReader(xmlReader, System.Windows.Markup.XamlReader.GetWpfSchemaContext());
XamlObjectWriter writer = new XamlObjectWriter(reader.SchemaContext);
writer.WriteStartObject(new XamlType(typeof(Page), reader.SchemaContext));
Attached is a project that shows how events\unknown elements could be filtered.