Anyone know Linq to XML?

[Durbs]

I need to parse some monster XML docs and have had a play with Linq to XML this morning - not used it before but looks good!

Can anyone point me in the right direction here, say i've got a simple XML doc:

<?xml version="1.0" ?> 
<SomeMetadata xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Versions>
<Version name="TheVersionName" description="TheVersionDesc">
<Properties>
<Property name="Version Name">TheVersionName</Property>
<Property name="Version Status">Working</Property>
</Properties>
<Hierarchies>
<Hierarchy name="Period" description="Period Hierarchy">
<Properties>
<Property name="Hier Name">Period</Property>
<Property name="Hierarchy Status">Working</Property> 
</Properties>
</Hierarchy>
<Hierarchy name="Currency" description="Currency Hierarchy">
<Properties>
<Property name="Hier Name">Currency</Property> 
<Property name="Hierarchy Status">Working</Property>
</Properties>
</Hierarchy>
</Hierarchies>
</Version>
</Versions>
</SomeMetadata>

I want to find out what the Version attributes are so i try:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim TheXmlDoc As New XDocument
        TheXmlDoc = XDocument.Load(Server.MapPath("XML/Test.xml"))

        Dim versions = From version In TheXmlDoc.Descendants("Version") _
                          Select VersionName = version.Attribute("name").Value, _
        VersionDesc = version.Attribute("description").Value, _
        VersionStatus = version.Element("Properties").Value

        For Each item In versions
            Response.Write("Version Name: " & item.VersionName & "<br />Version Description: " & item.VersionDesc _
                            & "<br />Version Status: " & item.VersionStatus)
        Next
End Sub

This returns:

Version Name: TheVersionName
Version Description: TheVersionDesc
Version Status: TheVersionNameWorking

What should my incorrect line 'VersionStatus = version.Element("Properties").Value' be so i can just grab the property value: name="Version Status" and get Version Status: Working? i.e i need to filter on the name value of the property attributes.

Ta.

[lightng]

Ahhh Lambda expressions.

Bit of a mouthful in programming terms, but try...


VersionStatus = version.Element("Properties").Elements("Property") .Where(Function(i) i.Attribute("name").Value = "Version Status").Value

[Durbs]

Ahhh Lambda expressions.

Bit of a mouthful in programming terms, but try...


VersionStatus = version.Element("Properties").Elements("Property") .Where(Function(i) i.Attribute("name").Value = "Version Status").Value

That only fookin works!!

You are a genius Mr Lightng and wasted in permiedom!!

[Weltchy]

Ahhh Lambda expressions.

Where(Function(i) i.Attribute("name").

Does the shorter version of Where(i=>i blah blah blah) still work?

[lightng]

Does the shorter version of Where(i=>i blah blah blah) still work?

In C#, yes.

[themistry]

When you say monster XML docs, how big are we talking?

Linq To XML doesn't stream the XML, meaning if your docs are 100mb in size (the infoset is approx 10x larger in memory), and your system is attempting to open a few of these at once... out of memory exceptions are likely.

Similarily, if you are trying to process 100 xml docs that are only 1mb each, thats roughly 1gb in memory.

Just something to think about in case it affects you.

TM

[Durbs]

When you say monster XML docs, how big are we talking?

Quite small really, not much data.

The monster bit is the data itself which is a load of separate interrelated hierarchies which i need to piece back together. This is no fun so i thought i'd have a play with Linq to see if it can help in other areas.

Cheers for the heads up though - whilst the data is currently viewed as minimal, we were planning to test with a very large dataset to see if it copes so i'll see if that causes issues.

[lightng]

LINQ is good but I tend to use the old .NET XML libraries to manipulate my XML. LINQ does enable developers to use the same methods to work with data whatever source it comes from but I think if developers are used to using XPATH, they'll tend to favour that over LINQ. One thing I like about XPATH is that you can avoid hard-coding queries; I also find it very readable.

I use LINQ to objects (business objects) a lot but I'm personally not that keen on LINQ to XML or LINQ to SQL.

[Durbs]

Was just Googling performance following themistry's post as was thinking i don't know how this data will grow:

http://www.nearinfinity.com/blogs/pa...linq_to_sql_vs

Guess i'll probably stick to the Reader just in case.

[themistry]

Was just Googling performance following themistry's post as was thinking i don't know how this data will grow:

http://www.nearinfinity.com/blogs/pa...linq_to_sql_vs

Guess i'll probably stick to the Reader just in case.

Using the XmlReader also has its challenges. Of the top of my head (I may have this confused with something else) it's a forward only reader, so xpaths that require lookups across axes, counts etc are not possible.

It's also harder to work with. I'd suggest sticking with your Linq direction, but run through some larger example files to ensure its ok.

Most XML files I have worked with are sub 100Kb, so unless you are doing anything extraordinary, i'd suggest saving yourself the hastle and using Linq to XML.

TM