[RESOLVED] Navigating through XML

[InvisibleDuncan]

I've got the following XML document that contains application settings:

<?xml version="1.0" encoding="utf-8" ?>
<Environment>

  <Live>
      <Database>LiveDB</Database>
      <Server>LiveServer</Server>
      <UserID>LiveID</UserID>
      <Password>LivePassword</Password>
      <DatabaseType>System.Data.SqlClient</DatabaseType>
  </Live>

  <UAT>
    <Database>UATDB</Database>
    <Server>UATServer</Server>
    <UserID>UATID</UserID>
    <Password>UATPassword</Password>
    <DatabaseType>System.Data.SqlClient</DatabaseType>
  </UAT>

  <Development>
    <Database>DevDB</Database>
    <Server>DevServer</Server>
    <UserID>DevID</UserID>
    <Password>DevPassword</Password>
    <DatabaseType>System.Data.SqlClient</DatabaseType>
  </Development>

</Environment>

I can get things at the end of a chain reasonably simply. For example, this code:

            Dim xpathDoc As XPathDocument = New XPathDocument("C\SettingsDocument.xml")
            Dim xmlNav As XPathNavigator = xpathDoc.CreateNavigator()
            Dim xmlNI As XPathNodeIterator

            xmlNI = xmlNav.Select("/Environment/UAT/Database")
            While xmlNI.MoveNext()
                MessageBox.Show(xmlNI.Current.Value)
            End While

... will return "UATDB". Easy.

The problem is that I'd like to get hold of a list of the environments, i.e. Live, UAT and Development. I had imagined that using the above code but swapping out the line

xmlNI = xmlNav.Select("/Environment/UAT/Database")

for

xmlNI = xmlNav.Select("/Environment")

would do it, but it doesn't - it basically retuns a string of all the end values: "LiveDBLiveServerLiveIDLivePasswordSystem.Data.SqlClientUATDBUATServerUATIDUATPasswordSystem.Data.Sq lClientDevDBDevServerDevIDDevPasswordSystem.Data.SqlClient". Not helpful.

So, does anyone know how I can get a list of the those environments out of that XML?

Much obliged.

[MattP]

Here's a couple of ways of going about it. I normally go about it using the methods shown in dev2 or dev3 depending on whether I need to have a strongly typed variable or whether an anonymous type will work.

Public Class Form1
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
 
        'Load xml file into XDocument
        Dim xdoc = XDocument.Load("C:\Temp\Environment.xml")
 
        'Select XElements from xdoc
        Dim selectedNodes = (From n In xdoc.<Environment>
                            Select n.<Live>, n.<UAT>, n.<Development>).FirstOrDefault()
 
        'Strongly typed from selectedNodes.Development
        Dim dev = (From n In selectedNodes.Development
                  Select New Development With
                         {
                             .Database = n.<Database>.Value,
                             .Server = n.<Server>.Value,
                             .UserId = n.<UserID>.Value,
                             .DevPassword = n.<Password>.Value,
                             .DatabaseType = n.<DatabaseType>.Value
                         }).FirstOrDefault()
 
        'Strongly typed from xdoc's descendant <Development>
        Dim dev2 = (From n In xdoc...<Development>
                   Select New Development With
                          {
                              .Database = n.<Database>.Value,
                              .Server = n.<Server>.Value,
                              .UserId = n.<UserID>.Value,
                              .DevPassword = n.<Password>.Value,
                              .DatabaseType = n.<DatabaseType>.Value
                          }).FirstOrDefault()
 
        'Anonymous type rather than using Development class
        Dim dev3 = (From n In xdoc...<Development>
                    Select New With
                          {
                              .Database = n.<Database>.Value,
                              .Server = n.<Server>.Value,
                              .UserId = n.<UserID>.Value,
                              .DevPassword = n.<Password>.Value,
                              .DatabaseType = n.<DatabaseType>.Value
                          }).FirstOrDefault()
    End Sub
End Class
 
Public Class Development
    Public Property Database As String
    Public Property Server As String
    Public Property UserId As String
    Public Property DevPassword As String
    Public Property DatabaseType As String
End Class

[techgnome]

I'd probably lay out the XML a little different from the start...

<Environments>
  <Environment Name="Live">
      <Database>LiveDB</Database>
      <Server>LiveServer</Server>
      <UserID>LiveID</UserID>
      <Password>LivePassword</Password>
      <DatabaseType>System.Data.SqlClient</DatabaseType>
  </Environment>
...
</Environments>

Or even

<Environments>
  <Environment Name="Live" Datablase="LiveDB" Server="LiveServer" UserID="LiveID" Password="LivePassword" Type="System.Data.SqlClient" />
...
</Environments>

-tg

[wild_bill]

I would use XML serialization.

Option Strict On
Option Explicit On

Imports System.Xml.Serialization

Namespace DataBase

    <XmlRoot("Environment")> _
    Public Class Environments

        Public Development As Information
        Public Live As Information
        Public UAT As Information

    End Class

    Public Class Information

        Public Database As String
        Public Server As String
        Public UserID As String
        Public Password As String
        Public DatabaseType As String

    End Class

End Namespace

    Private Sub frmMain_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        'get data from file
        Dim xmlData = IO.File.ReadAllText("C:\temp1\Environment.xml")
        'create object from data
        Dim o = DeserializeFromString(xmlData)

    End Sub

    Private Function DeserializeFromString(ByVal input As String) As DataBase.Environments

        'Convert to byte array
        Dim encoding As New System.Text.UTF8Encoding
        Dim bytes() As Byte = encoding.GetBytes(input)

        'read bytes into stream
        Dim ms As New System.IO.MemoryStream
        ms.Write(bytes, 0, bytes.Length)
        ms.Position = 0

        'get object from bytes
        Dim xs As New Xml.Serialization.XmlSerializer(GetType(DataBase.Environments))
        Return DirectCast(xs.Deserialize(ms), DataBase.Environments)

    End Function

[InvisibleDuncan]

Thanks for all the advice, folks. Unfortunately, MattP's code is for 2010 and Bill's seems to need me to already know what the possible environments are, when the problem is that I won't know until I extract them from the XML. It's quite possible I've misunderstood, though.

I've tweaked the XML slightly (not quite as suggested by TG), and I've now been able to do what I was after:

<Environments>
  <Environment>
      <EnvironmentName>Live</EnvironmentName>
      <Database>LiveDB</Database>
      <Server>LiveServer</Server>
      <UserID>LiveID</UserID>
      <Password>LivePassword</Password>
      <DatabaseType>System.Data.SqlClient</DatabaseType>
  </Environment>
...
</Environments>

    Public Shared Function GetEnvironments() As List(Of String)
        Dim Environments As List(Of String) = New List(Of String)

        Try
            '# Our configuration file holds properties based on the environment.
            '# Return a list of these environments.
            Dim xmlDoc = XDocument.Load(SettingsDocument)

            For Each EnvironmentXML In xmlDoc...<Environment>
                Environments.Add(EnvironmentXML...<EnvironmentName>.Value)
            Next

            Return Environments

        Catch ex As Exception
            WriteLog(ex)
            Return Environments
        End Try

    End Function

The only problem is, I now can't do something which I could with the original layout - that is, to find a specific element while using a variable:

    Public Shared Function GetApplicationSetting(ByVal settingName As String) As String

        Dim Setting As String = String.Empty
        Try
            '# Setting is held in the configuration file as a global setting.
            Dim xpathDoc As XPathDocument = New XPathDocument(SettingsDocument)
            Dim xmlNav As XPathNavigator = xpathDoc.CreateNavigator()
            Dim xmlNI As XPathNodeIterator

            xmlNI = xmlNav.Select("/Environment/Global/" & settingName)
            While xmlNI.MoveNext()
                Setting = xmlNI.Current.Value
            End While

            Return Setting

        Catch ex As Exception
            WriteLog(ex)
            Return Setting
        End Try

    End Function

Stepping though this shows that it steps straight out of the loop, meaning that there's no .MoveNext to be performed. The xmlNI.Current.Value is back to being "LiveDBLiveServerLiveIDLivePasswordSystem.Data.SqlClientUATDBUATServerUATIDUATPasswordSystem.Data.Sq lClientDevDBDevServerDevIDDevPasswordSystem.Data.SqlClient".

I think I'm just making matters worse!

[InvisibleDuncan]

By the way, I can obviously see why that old code isn't working - I just can't see what I need to change it to.

[InvisibleDuncan]

Okay, I've managed to get something working having rejigged my XML as suggested by TG.

        Try

            Dim xmlDoc As Xml.XmlDocument = New Xml.XmlDocument
            xmlDoc.Load(SettingsDocument)

            Dim MainNodes As Xml.XmlNodeList = xmlDoc.GetElementsByTagName("Environment")

            For Each ChildNode As Xml.XmlNode In MainNodes
                Debug.Print(ChildNode.Attributes.GetNamedItem("Name").Value) '# Environment name: Live, UAT etc
                For Each InnerNode As XmlNode In ChildNode.ChildNodes
                    Debug.Print(InnerNode.LocalName & " = " & InnerNode.InnerText) '# Element, e.g. UserID = LiveUserID
                Next InnerNode
            Next ChildNode

        Catch ex As Exception
        End Try

It's a little clumsy as it needs to loop through to find everything rather than jumping to the correct node to start with, but at least it works.

[MattP]

Unfortunately, MattP's code is for 2010

It should work under 2008 with the addition of underscores at the line breaks.

Glad you got a solution that works for you though.

[InvisibleDuncan]

Thanks, Matt - I hadn't realised that. I think I might investigate your suggestion a bit more, because it looks very interesting and completely different to what I've tried before. I'm all for learning something new.

In the meantime, I did find a simple way of getting at individual elements:

        Dim xmlDoc As Xml.XmlDocument = New Xml.XmlDocument
        xmlDoc.Load(SettingsDocument)

        Dim MainNodes As Xml.XmlNodeList = xmlDoc.SelectNodes("/Environments/Environment[@Name='Development']")

        For Each ChildNode As Xml.XmlNode In MainNodes
            Debug.Print(ChildNode.Attributes.GetNamedItem("Name").Value) '# Environment name: Live, UAT etc
            Debug.Print(ChildNode.SelectSingleNode("Database").InnerXml)
            Debug.Print(ChildNode.SelectSingleNode("Server").InnerXml)
            Debug.Print(ChildNode.SelectSingleNode("UserID").InnerXml)
            Debug.Print(ChildNode.SelectSingleNode("Password").InnerXml)
        Next ChildNode

Thanks to everyone for their help - it's much appreciated.

[techgnome]

yeah, you shouldn't have to loop through the nodes to find the one you want... you really only need to loop when you want them all, or not sure what you're looking for... the xQuery you have there should be perfect, and would be how I'd roll with it too ... until someone like Matt comes along and points out the LINQ version, and I'd go "oh sweet!" and then re-write everything... :P

-tg