Derik Whittaker

Originally this series was meant to be titled 'Any thing you can do I can do better', but to be honest after writing the Xml/XPath examples I realized the XLinq is really no better per say than Xml/XPath.  However, what XLinq does bring to the table that Xml/XPath does not:

• Does not need to use the XPath query syntax
• Reads like English (mostly) when creating queries
• Lower barrier to entry for someone new to Xml (my opinion)

In Part 1 of this little mini series we will examine some common data access scenario's and how XLinq's syntax compares to that of standard Xml/XPath access.

Before I get started I will show you a sample of the XML document I am using.

<?xml version='1.0'?>
<root>
  <system>
    <list>
      <subscribers>
        <subscriber Type="Random">
          <id>63425813</id>
          <Email__Address>FakeAddress@comcast.net</Email__Address>
          <EmailType>HTML</EmailType>
          <Status>InActive</Status>
          <First__Name>RAY</First__Name>
          <Last__Name>Bob</Last__Name>
          <PIN__Code>NaN</PIN__Code>
          <PIPIN>33232</PIPIN>
          <UID>418444</UID>
          <ProgNum>0</ProgNum>
          <Title />
          <Username />
          <Password />
        </subscriber>
      </subscribers>
    </list>
    <list>
      <subscribers>
          <subscriber>
          <id>1271728821</id>
          <Email__Address>FakeAddress@yahoo.com</Email__Address>
          <EmailType>HTML</EmailType>
          <Status>InActive</Status>
          <First__Name>JOHN</First__Name>
          <Last__Name>Foo</Last__Name>
          <PIN__Code>NaN</PIN__Code>
          <PIPIN>1254512</PIPIN>
          <UID>1033488</UID>
          <ProgNum />
          <Title />
          <Username />
          <Password />
        </subscriber>
      </subscribers>
    </list>
  </system>
</root>

Example 1 - Simple data access

via Xml/XPath

XmlDocument xmlDocument = XmlHelper.GetRawSnippetAsXmlDocument();

// notice the @ is on the status -- this is how u search a element
Int32 listCount = xmlDocument.SelectNodes( "//list" ).Count;
Int32 subscribersCount = xmlDocument.SelectNodes( "//subscriber[@Type='Random']" ).Count;

via XLinq

XDocument xDocument = XmlHelper.GetRawSnippetAsXDocument();

Int32 listCount = xDocument.Descendants( "list" ).Count();
Int32 subscribersCount = xDocument.Descendants( "subscriber" ).Attributes( "Type" ).Where( e => e.Value == "Random" ).Count();

As you can see both examples are pretty light on the code and are pretty straight forward.  This is one case where the new XLinq syntax is really no better/simpler then the Xml/XPath syntax.  The issue with the XPath syntax is that

Example 2 - Get a list of nodes that match our search criteria

via Xml/Xpath

// notice the @ is missing on the status -- this is how u search a node
XmlDocument xmlDocument = XmlHelper.GetRawSnippetAsXmlDocument();
XmlNodeList xmlNodeList = xmlDocument.SelectNodes( "//subscribers/subscriber[Status='InActive']" );

foreach ( XmlElement element in xmlNodeList )
{
    var id = element.SelectSingleNode( "//id" ).InnerText;
    var type = element.Attributes[ "Type" ].Value;
}

via XLinq

XDocument xDocument = XmlHelper.GetRawSnippetAsXDocument();

var item = from doc in xDocument.Descendants( "subscriber" )
           let status = (string)doc.Element( "Status" )
           where status == "InActive"
           select doc;

foreach ( XElement xElement in item )
{
    var id = xElement.Element( "id" ).Value;
    var type = xElement.Attribute( "Type" ).Value;
}

Now here is an example where I think the XLinq syntax is cleaner and easier to understand.  There is no need to know or understand the XPath syntax, which can be a pain to learn.  Also here you see how XLinq looks a lot like standard SQL syntax and should be familiar to most developers.

Well, above I have shown you a few simple examples that compare Xml/Path to XLinq, I hope you find this useful.  The next post will compare how to update/add data to a document using the both Xml/XPath and XLinq.

Till next time,