Trying to count named XML elements filtered by parent element name and index value

Question

I have been just about managing to manipulate XML in VB.net but I've run into a problem I'm really struggling with, so I'm reaching out for a little guidance please?!

With this example XML...

<?xml version="1.0" encoding="utf-8"?>
<dataset>
  <packages>
    <package index="1">
      <desc>First Package</desc>
      <rmabool>1</rmabool>
      <rmaref>RMACASE1</rmaref>
      <bootfiles>1</bootfiles>
      <image>1</image>
      <driver>3</driver>
      <driver>4</driver>
    </package>
    <package index="2">
      <desc>Second Package</desc>
      <bootfiles>2</bootfiles>
      <image>2</image>
      <driver>3</driver>
    </package>
    <package index="3">
      <desc>Third Package</desc>
      <bootfiles>3</bootfiles>
      <image>2</image>
      <driver>3</driver>
    </package>
  </packages>
</dataset>

...I would like to count how many elements, named 'driver', are contained in an element named 'package' with an index matching "1". I would expect the result to be returned is "2", or if I change the search to match index with "3" then I would expect the result is "1".

Elsewhere I have a simple sub which returns a count of elements only matching a name, below is my effort to modify this but I cannot get it to work...

Public Function CountElementDescendents(ByVal CFGFile As String,_ 'Path to Config.xml
                                        ByVal Perent As String,_ 'Name of element to search descendents eg. 'package'
                                        ByVal ParentIndex As String,_ 'Index value of element to search descendents eg. '1'
                                        ByVal ElementCount As String_ 'Name of descendent elements to count 'eg. 'driver'
                                        ) As Integer 'Return number of matching elements eg. '2'
    Dim ReturnValue As Integer = 0
    Dim Xe As XElement

    Xe = XElement.Load(CFGFile)
    Dim Query As IEnumerable(Of XElement) = Xe.Elements(Perent).Attribute("index="&ParentIndex).Descendants(ElementCount)
    
    ReturnValue = Query.Count()
    CountElementDescendents = ReturnValue
End Function

I'm not sure if this is possible or even if I have taken the best approach of structuring my XML, can someone offer some assistance or advice please? Thanks!

Thanks to @dbasnett and @Craig for their help, you're awesome! I'll mark this as answered.

dbasnett · Accepted Answer · 2020-06-23T16:32:14.280

Give this a try. The LINQ query examines all driver elements and selects those whose parent is a package with an index of 1.

    'for testing use XML literal
    Dim xe As XElement
    xe = <dataset>
             <packages>
                 <package index="1">
                     <desc>First Package</desc>
                     <rmabool>1</rmabool>
                     <rmaref>RMACASE1</rmaref>
                     <bootfiles>1</bootfiles>
                     <image>1</image>
                     <driver>3</driver>
                     <driver>4</driver>
                 </package>
                 <package index="2">
                     <desc>Second Package</desc>
                     <bootfiles>2</bootfiles>
                     <image>2</image>
                     <driver>3</driver>
                 </package>
                 <package index="3">
                     <desc>Third Package</desc>
                     <bootfiles>3</bootfiles>
                     <image>2</image>
                     <driver>3</driver>
                 </package>
             </packages>
         </dataset>

    ' I would like to count how many elements, named 'driver', 
    '  are contained in an element named 'package' with an index matching "1". 
    '
    Dim ie As IEnumerable(Of XElement)
    ie = From el In xe...<driver>
         Where el.Parent.Name.LocalName = "package" AndAlso el.Parent.@index = "1"
         Select el

edit: As function

Private Function Srch(ElementToSearch As XElement,
                         ParentName As String,
                         ParentIndex As String) As IEnumerable(Of XElement)

    Dim ie As IEnumerable(Of XElement)
    ie = From el In ElementToSearch...<driver>
         Where el.Parent.Name.LocalName = ParentName AndAlso el.Parent.@index = ParentIndex
         Select el

    Return ie

End Function

edit 2 - updated function

Private Function Srch(ElementToSearch As XElement,
                         FindThis As String,
                         ParentName As String,
                         ParentIndex As String) As IEnumerable(Of XElement)

    Dim ie As IEnumerable(Of XElement)

    ie = From el In ElementToSearch.Descendants(FindThis)
         Where el.Parent.Name.LocalName = ParentName AndAlso el.Parent.@index = ParentIndex
         Select el

    Return ie

End Function

Tested with

    Dim rslts As IEnumerable(Of XElement)
    rslts = Srch(xe, "bootfiles", "package", "1")

Hi dbasnett, that's fantastic and works a treat, thank you so much! I have just one last question, I've modified the query so I can search using the subroutines variables like this `ie = From el In xe... Where (el.Parent.Name.LocalName = Perent AndAlso el.Parent.@index = ParentIndex) Select el` but I'm not sure how to pass 'driver' from outside the subroutine, is this also possible? — Darryl, Jun 23 '20 at 13:19
That looks good also, but what if i need to count 'bootfiles' instead of 'drivers' will that do it? — Darryl, Jun 23 '20 at 13:54
I don't know if it would work in this context, but the usual way of doing inline code-to-XML is usually to enclose in '<%=' and '%>'; I've only done that for values, so I'm not sure it it would work the same way for tags. — Craig, Jun 23 '20 at 14:03
Thank you Craig, that looks like the kind of solution I need, however, I'm getting an 'XML name expected' error using that method, sorry. — Darryl, Jun 23 '20 at 14:18
@dbasnett thank you, that's much more elegant than my work-around! — Darryl, Jun 23 '20 at 16:41

Trying to count named XML elements filtered by parent element name and index value

1 Answers1