read an xml stream

Question

Hi. I am trying to read the following xml stream but am really struggling.

<channelSnapshot xmlns="urn:betfair:games:api:v1">
<channel gameType="BLACKJACK" id="1444077" name="Exchange BlackJack">
<status>RUNNING</status>
<game id="190675">
<round>1</round>
<bettingWindowTime>30</bettingWindowTime>
<bettingWindowPercentageComplete>100</bettingWindowPercentageComplete>
<gameData>
<object name="Player 1">
<description/>
<status>IN_PLAY</status>
<property name="Card 1" value="NOT AVAILABLE"/>
<property name="Card 2" value="NOT AVAILABLE"/>
</object>

The stream is acquired in the following way

  Dim dataStream As Stream = response.GetResponseStream()
  Dim reader As New XmlTextReader(dataStream)

If the element is between a start tag and end tag such as

 <status>RUNNING</status>

Then I can access the value ok. I have been using Select Case xmlnodetype but using this when the nodetype is a whitespace I can't get to the element beyond the whitespace.So that in the following line

 <property name="Card 1" value="NOT AVAILABLE"/>

I cant get to anything beyond the word property.

As must be obvious this is all new to me, so I would welcome all and any help.

Answer 1

You'll need to read them as attributes. See the GetAttribute() method.

For instance:

Dim cardName as String = reader.GetAttribute("name")

Answer 2

You should consider using XmlReaderSettings when creating your XmlReader to simplify parsing the underlying stream (i.e. XmlReaderSettings.IgnoreWhitespace).

Then, you should be able to parse the stream in a manner similar to the following.

using (XmlReader reader = XmlReader.Create(dataStream))
{
    while(reader.Read())
    {
        switch(reader.NodeType)
        {
            case XmlNodeType.Element:
            // do something

            case XmlNodeType.Attribute:
            // do something

            // etc...
        }
    }
}

Also, inspect the properties and methods of the XmlReader base class to determine how to get at elements, attributes, and other XML entities.

Answer 3

Your XML is not well-formed. You've got open tags with no close tags. If you had indented your XML, you would have seen that.

Also, unless you're stuck using .NET 1.1, you should not use XmlTextReader. Use XmlReader.Create.

In addition to using XmlReader directly, you might want to look at LINQ to XML, which provides a somewhat simpler model for searching XML, or the older XmlDocument, which you can load from an XmlReader.

Answer 4

How about a different approach? Processing the stream as you are currently doing seems to be pretty hard work.

If you instead read the whole stream into a string and then load that string into an XDocument you'll be able to process the file much easier.

VB allows you to access date from Xml files in a very easy way, take a look at the following code to see what I mean:

' get the response stream so we can read it
Dim responseStream = response.GetResponseStream()
' create a stream reader to read the response
Dim responseReader = New IO.StreamReader(responseStream)
' read the response text (this should be javascript)
Dim responseText = responseReader.ReadToEnd()

' load the response into an XDocument
Dim xmlDocument = XDocument.Parse(responseText)

' find all the player objects from the document
For Each playerObject In xmlDocument...<object>

    ' display the player's name (this is how you access an attribute)
    Console.WriteLine("Player name: {0}", playerObject.@name)
    ' display the player's status (this is how you access an element)
    Console.WriteLine("Player status: {0}", playerObject.<status>.Value)

Next

To get your player properties you can do the following:

' go through the player's properties
For Each playerProperty In playerObject...<property>
    ' output the values
    Console.WriteLine("Player property name: {0}", playerProperty.@name)
    Console.WriteLine("Player property value: {0}", playerProperty.@value)
Next

As somebody else mentioned, your Xml is malformed, but the XDocument will tell you about this so you'll be able to fix it.