Question

I’m still somewhat new to Visual Basic and XML so I don’t know if I’m phrasing this correctly. I have only scratched the surface of XSLT, but from what I’ve seen so far I don’t know if it can do this.

I am trying to recursively sort an XML file alphabetically by its tags in Visual Basic. For example, for an XML document, such as:

<catalog>
  <game>
      <title>Role-playing EXTREME Adventure</title>
      <platform>PC</platform>
      <type>Action/Adventure</type>
      <price>60.00</price>
  </game>
  <cd>
      <title>Music Notes</title>
      <artist>Susan Dylan</artist>
      <genre>Rock</genre>
      <company>Columbia</company>
      <year>1995</year>
      <price>10.95</price>
  </cd>
  <book>
      <title>Pictures of Things</title>
      <author>Bob Smith</author>
      <type>paper-back</type>
      <price>5.99</price>
  </book>
</catalog>

…becomes:

<catalog>
  <book>
      <author>Bob Smith</author>
      <price>5.99</price>
      <title>Pictures of Things</title>
      <type>paper-back</type>
  </book>
  <cd>
      <artist>Susan Dylan</artist>
      <company>Columbia</company>
      <genre>Rock</genre>
      <price>10.95</price>
      <title>Music Notes</title>
      <year>1995</year>
  </cd>
  <game>
      <platform>PC</platform>
      <price>60.00</price>
      <title>Role-playing EXTREME Adventure</title>
      <type>Action/Adventure</type>
  </game>
</catalog>

This sorted version should replace the contents of the XML file and be saved. This will be done for multiple, long XML files. I’m not at my work computer, so I don’t have access to the mess of Visual Basic code that I had been fiddling with. I’m beginning to think I should discard what I’ve done anyway though.

I apologize if this is answered somewhere. I spent most of the day searching and working on this. So if there is already an answer, I look forward to getting a link to it. 🙂

I saw this but it doesn’t seem to meet my needs. It must be done from within a Visual Basic and not a command line.

I appreciate any help.

Answer 1

Here’s a program you can use to sort XML (you’ll need at least .NET 3.0 to use LINQ to XML and extension methods, but this can also be accomplished with the old-style XML parsing libraries and regular methods):

Imports System.Xml.Linq
Imports System.Runtime.CompilerServices

Module Module1

Sub Main()
    Dim xe As XElement = XElement.Load("test.xml")
    Console.WriteLine("----Original XML----")
    Console.WriteLine(xe)
    xe.SortRecursive()
    Console.WriteLine("----Sorted XML----")
    Console.WriteLine(xe)
End Sub

''' <summary>
''' Sorts the subelements of an XML element, and their subelements recursively.
''' </summary>
''' <param name="xe"></param>
''' <remarks></remarks>
<Extension()>
Sub SortRecursive(xe As XElement)
    xe.Sort()
    For Each subelement As XElement In xe.Elements()
        subelement.SortRecursive()
    Next
End Sub

''' <summary>
''' Sorts the subelements of an XML element.
''' </summary>
''' <param name="xe">The element whose subelements are to be sorted.</param>
<Extension()>
Sub Sort(xe As XElement)
    ' Save off the subelements into a list, and remove them from the main element
    Dim subelements As New List(Of XElement)
    For Each subelement As XElement In xe.Elements().ToArray()
        subelement.Remove()
        subelements.Add(subelement)
    Next

    ' Sort the list of subelements
    subelements.Sort(AddressOf CompareElementNames)

    ' Add the elements back and return when done
    For Each subelement As XElement In subelements
        xe.Add(subelement)
    Next
End Sub

''' <summary>
''' Compares two XML elements by their names.
''' </summary>
''' <param name="e1">The first element.</param>
''' <param name="e2">The second element.</param>
''' <returns>positive/negative/zero depending on comparison (same as string comparison)</returns>
Function CompareElementNames(e1 As XElement, e2 As XElement) As Integer
    Return String.Compare(e1.Name.ToString(), e2.Name.ToString())
End Function
End Module