How can I use DataContractSerializer to deserialize from a single node of an XMLDocument?

Question

The readers that DataContractSerializer uses in ReadObject seem to be stream-based. I already have an XMLDocument, and I would like to deserialize one part of that document.

In this code snippet, I am deserializing a MyItem object from a filestream:

Dim fs As New FileStream("c:\myinputfile.xml", FileMode.Open)
Dim reader As XmlDictionaryReader = XmlDictionaryReader.CreateTextReader(fs, New XmlDictionaryReaderQuotas())
Dim ser As New DataContractSerializer(GetType(MyItemClass))
Dim deserializedMyItem As ClassTemplate = CType(ser.ReadObject(reader, True), MyItemClass)

but what if instead I want to deserialize just a part of a document.

Dim MyItemNode as Xml.XmlNode = parentDoc.selectSingleNode("MyItemElementName")
Dim deserializedMyItem As MyItemClass = getMyItemFromNode(MyItemNode)

What does getMyItemFromNode look like?

Possibilities seem to be converting the node to a memory stream or copying it to a new document, but it seems like there should be an easier way. — pc1oad1etter, Jan 12 '11 at 15:46

score 0 · Answer 1 · edited May 23 '17 at 11:48

Unless there is a better way that streaming it, here's a solution using the memorystream:

Function getMyItemFromNode(ByVal itemNode as Xml.XmlNode) as MyItemClass
    Dim stm As New MemoryStream()
    Dim stw  As New StreamWriter(stm)
    stw.Write(itemNode.OuterXml)
    stw.Flush()
    stm.Position = 0
    Dim reader As XmlDictionaryReader = XmlDictionaryReader.CreateTextReader(stm, New XmlDictionaryReaderQuotas())
    Dim ser As New DataContractSerializer(GetType(MyItemClass))
    Return CType(ser.ReadObject(reader, True), MyItemClass)

End Function

Code for pushing it to a stream came from this response to a related question.

score 0 · Answer 2 · answered Jan 13 '11 at 00:38

Use [CreateDictionaryReader](http://msdn.microsoft.com/en-us/library/system.xml.xmldictionaryreader.createdictionaryreader.aspx) with anXmlReader` pointing to the node you want:

Dim doc As XmlDocument = new XmlDocument()
' fill it

Dim nav as XPathNavigator = doc.CreateNavigator()
Dim docReader As XmlReader = nav.ReadSubTree()
Dim reader As XmlDictionaryReader = _
    XmlDictionaryReader.CreateDictionaryReader(docReader)
Dim ser As New DataContractSerializer(GetType(MyItemClass))

How can I use DataContractSerializer to deserialize from a single node of an XMLDocument?

2 Answers2