Testing DataContractSerializer with String

Question

I'm testing sending a complex message object over a WCF service and getting various serialization errors. In order to simplify things I'm trying to cut it down to just testing the DataContractSerializer, for which I've written the following test based on the code here:

Dim message As TLAMessage = MockFactory.GetMessage
Dim dcs As DataContractSerializer = New DataContractSerializer(GetType(TLAMessage))
Dim xml As String = String.Empty

Using stream As New StringWriter(), writer As XmlWriter = XmlWriter.Create(stream)
    dcs.WriteObject(writer, message)
    xml = stream.ToString
End Using

Debug.Print(xml)

Dim newMessage As TLAMessage
Dim sr As New StringReader(xml)
Dim reader As XmlReader = XmlReader.Create(sr)
dcs = New DataContractSerializer(GetType(TLAMessage))
newMessage = CType(dcs.ReadObject(reader, True), TLAMessage) 'Error here
reader.Close()
sr.Close()

Assert.IsTrue(newMessage IsNot Nothing)

However this gets an unusual error in itself on the call to ReadObject: Unexpected end of file while parsing Name has occurred. Line 1, position 6144

It appears to be a buffering error but I can't see how to 'ReadToEnd' on the string. I've tried using a MemoryStream: Dim ms As New MemoryStream(Encoding.UTF8.GetBytes(xml)) and a StreamWriter but each of those has come with their own errors or are not compatible with the ReadObject method of the DataContractSerializer which takes a variety of different overloads.

Note that adapting the code from the MSDN page works fine but requires serializing to a file, however I wanted to serialize to and from a string but I think that I'm missing something vital.

Am I missing something obvious in the code above?

Answer 1

The data from your XmlWriter is not immediately populated to the underlying StringWriter. So you should flush the writer after writing:

dcs.WriteObject(writer, message)
writer.Flush()
xml = stream.ToString()