XML Pathfinder - A Visual Basic Utility

Introduction:

This article discusses the construction of a simple utility that may be used to locate and evaluate paths within an XML document, and to test queries against those paths. The application allows the user to open an XML document into a TreeView control for easy viewing of the structure; the user may right click on any node within the TreeView to expose a context menu that will allow the user to copy the current path to that node. The user may then open a test window up and paste the copied path into an expression text box. Once the path has been pasted into the text box, the user may test the path directly, or may edit the path and test the edit.

The project includes a collection of sample XML documents which may be used to try out the application.

To use the application, open the main form and use the file menu to open an xml document. The document will be displayed in the main form using a TreeView control. The user may click on any node in the TreeView and the path to that node as well as the node type will be displayed in the status bar at the bottom of the window. The user may right click on any selected node and select from one of three options:

1. Copy only the text contained in the current node,
    
2. Copy the path to the node formatted as a query for that attribute value, and
    
3. Copy the full path exactly as it is.

Figure 1: Context Menu



Figure 2: The Main Form



Figure 3: The Test Form (Example shows use of the "Copy Full Path to Query an Attribute" context menu option)



Figure 4: Editing a path manually to test alternative paths ("/description" added to path shown in Figure 3)

The intent of the application was to provide a simple tool that may be used to test paths for XPath based queries; it is intended to simplify viewing the XML and to make it easier to identify specific paths within an XML document.

Getting Started:

In order to get started, unzip the included project and open the solution in the Visual Studio 2005 environment. In the solution explorer, you should note these files:



Figure 5: Solution Explorer

The Main Form (frmXmlPathfinder.vb).

The main form is used to open XML documents and to display them in TreeView format; form also provides the interface necessary to copy node paths and to open a test window which may be used to test XPath based queries against the XML document's content. The code is annotated and should be easy enough to follow from the descriptions provided:
If you'd care to open the code view up in the IDE you will see that the code file begins as follows:

Imports System.Xml
Imports System.Xml.XPath

Note that the additions of the System.Xml and System.Xml.XPath libraries are the only departure from the default.

Following the imports, class is defined and a constructor added. A local string variable it declared and used to hold the path to the XML document.

Public Class frmXmlPathfinder

    ' Member variables
    Private mFilePath As String

    ''' <summary>
    ''' Constructor
    ''' </summary>
    ''' <remarks></remarks>

    Public Sub New() 

        ' This call is required by the Windows Form Designer.
 

        InitializeComponent()

 

        ' Add any initialization after the InitializeComponent() call.

 

        ' init the file path as empty

        mFilePath = String.Empty

 

    End Sub

Next up is the method used to exit the application.
 

    ''' <summary>

    ''' Exit the Application

    ''' </summary>

    ''' <param name="sender"></param>

    ''' <param name="e"></param>

    ''' <remarks></remarks>

    Private Sub tspExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tspExit.Click

 

        Application.Exit()

 

    End Sub

The next section of the code is used to load the XML document into the TreeView control.
 

    ''' <summary>

    ''' Write the xml document into a treeview to make

    ''' easier to read and navigate, starting with the top

    ''' of the document, the method uses recursion to

    ''' populate the treeview with all the child nodes

    ''' </summary>

    ''' <param name="currentNode"></param>

    ''' <param name="nodCollection"></param>

    ''' <remarks></remarks>

    Private Sub PushToTreeView(ByVal currentNode As XmlNode, _ ByVal nodCollection As TreeNodeCollection)

 

        Try
       

            Dim insertNode As TreeNode = nodCollection.Add(currentNode.Name)

 

            Select Case (currentNode.NodeType)

 

                Case XmlNodeType.Element

                    insertNode.Text = currentNode.Name

                    insertNode.Tag = "Element"

                    insertNode.ImageIndex = 1

                Case XmlNodeType.Attribute

                    insertNode.Text = "@" + currentNode.Name

                    insertNode.Tag = "Attribute"

                    insertNode.ImageIndex = 2

                Case XmlNodeType.Text

                    insertNode.Text = currentNode.Value

                    insertNode.Tag = "Text"

                    insertNode.ImageIndex = 3

                Case XmlNodeType.CDATA

                    insertNode.Text = currentNode.Value

                    insertNode.Tag = "CDATA"

                    insertNode.ImageIndex = 4

                Case XmlNodeType.Comment

                    insertNode.Text = currentNode.Value

                    insertNode.Tag = "Comment"

                    insertNode.ImageIndex = 5

                Case XmlNodeType.Entity

                    insertNode.Text = currentNode.Value

                    insertNode.Tag = "Entity"

                    insertNode.ImageIndex = 6

                Case XmlNodeType.Notation

                    insertNode.Text = currentNode.Value

                    insertNode.Tag = "Notation"

                    insertNode.ImageIndex = 7

                Case Else

                    ' do nothing

 

            End Select

 

            ' Recursive stuff

 

            ' check the current node for attributes

            If Not currentNode.Attributes Is Nothing Then

 

                ' write out the attributes to the treeview

                Dim attribute As XmlAttribute

                For Each attribute In currentNode.Attributes

                    PushToTreeView(attribute, insertNode.Nodes)

                Next

 

            End If

 

            ' check the current node for child nodes

            If Not currentNode Is Nothing And currentNode.HasChildNodes Then

 

                ' write out the child nodes to the treeview

                Dim childNode As XmlNode

                For Each childNode In currentNode.ChildNodes

                    PushToTreeView(childNode, insertNode.Nodes)

                Next

 

            End If

 

        Catch ex As Exception

 

            MessageBox.Show(ex.Message, "Error Reading XML Document")

 

        End Try

 

    End Sub

The next method is used to load up a new XML document into the form.
 

    ''' <summary>

    ''' Open an xml document into the treeview

    ''' </summary>

    ''' <param name="sender"></param>

    ''' <param name="e"></param>

    ''' <remarks></remarks>

    Private Sub tspOpen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tspOpen.Click

 

        Try

 

            openFileDialog1.Title = "Open XML File"

            openFileDialog1.Filter = "XML Files|*.xml"

            openFileDialog1.DefaultExt = "XML"

            openFileDialog1.FileName = ""

 

            openFileDialog1.ShowDialog()

 

            If openFileDialog1.FileName = "" Then

                Return

            End If

 

            ' set the file path member var

            mFilePath = openFileDialog1.FileName

 

            ' Clear the treeview.

            treeXml.Nodes.Clear()

 

            ' set the wait cursor

            Me.Cursor = Cursors.WaitCursor

 

            ' create a new xml doc

            Dim doc As New XmlDocument()

 

            Try

 

                ' load the xml doc

                doc.Load(mFilePath)

 

                ' set the form text to include

                ' the file name

                Me.Text = "XML Pathfinder - " + mFilePath

 

                ' return the cursor

                Me.Cursor = Cursors.Default

 

            Catch ex1 As Exception

 

                ' return the cursor

                Me.Cursor = Cursors.Default

 

                ' tell a story

                MessageBox.Show(ex1.Message, "Error Opening XML File")

                Return

 

            End Try
 

            ' open the doc into the treeview for

            ' inspection

            PushToTreeView(doc, treeXml.Nodes)

 

            ' restore the cursor

            Me.Cursor = Cursors.Default 

 

        Catch ex2 As Exception

 

            ' snitch

            MessageBox.Show(ex2.Message, "Unable to Open Document")

 

        End Try

 

    End Sub

The next bit of code is used display the selected node's path within the context of the XML document; the path shown is a cleaned up version of what appears in the TreeView. This code will display both the path as well as the selected node's type (e.g., Element, or Attribute).
 

    ''' <summary>

    ''' Update the status bar when a new node is selected

    ''' </summary>

    ''' <param name="sender"></param>

    ''' <param name="e"></param>

    ''' <remarks></remarks>

    Private Sub treeXml_AfterSelect(ByVal sender As System.Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles treeXml.AfterSelect

 

        Try

 

            Dim tmp As String = treeXml.SelectedNode.FullPath

            tmp = tmp.Replace("#document", "/")

 

            ' show the path in the status bar

            statusPath.Text = "Selected Path: " + tmp

 

            ' show the selected node type in the status bar

            statusType.Text = "Selected Type: " +  treeXml.SelectedNode.Tag

 

        Catch

 

            ' skip this update

 

        End Try

    End Sub

The next three methods are used to format the path and to copy it into the clipboard making it possible to then paste the selected path directly into the expression test text box on the test form.
 

    ''' <summary>

    ''' Update the status bar when a new node is selected

    ''' </summary>

    ''' <param name="sender"></param>

    ''' <param name="e"></param>

    ''' <remarks></remarks>

    Private Sub treeXml_AfterSelect(ByVal sender As System.Object, ByVal e As

    System.Windows.Forms.TreeViewEventArgs) Handles treeXml.AfterSelect

 

        Try

 

            Dim tmp As String = treeXml.SelectedNode.FullPath

            tmp = tmp.Replace("#document", "/")

 

            ' show the path in the status bar

            statusPath.Text = "Selected Path: " + tmp

 

            ' show the selected node type in the status bar

            statusType.Text = "     Selected Type: " +

            treeXml.SelectedNode.Tag

 

        Catch

 

            ' skip this update

 

        End Try

 

    End Sub

The last two methods in the main form are used to either open a help window or to open a test window.

    ''' <summary>

    ''' Open the test file if there is an active

    ''' xml file open in the main form

    ''' </summary>

    ''' <param name="sender"></param>

    ''' <param name="e"></param>

    ''' <remarks></remarks>

    Private Sub tspOpenTest_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tspOpenTest.Click

 

        If mFilePath <> String.Empty Then

 

            Dim f As New frmTest(mFilePath)

            f.Show()

 

        Else

 

            MessageBox.Show("Open an xml document prior to starting a test.",

            "Invalid File")

 

        End If

 

    End Sub 

 

    ''' <summary>

    ''' Open the help file

    ''' </summary>

    ''' <param name="sender"></param>

    ''' <param name="e"></param>

    ''' <remarks></remarks>

    Private Sub tspOpenHelp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tspOpenHelp.Click

 

        Dim f As New frmHelp()

        f.Show()

 

    End Sub

 

End Class

The Test Form (frmTest.vb).

The test form is used to test paths within open XML documents and to display of any XPath type queries executed against the XML document.

If you'd care to open the code view up in the IDE you will see that the code file begins as follows:

 

Imports System.IO

Imports System.Text

Imports System.Xml

Imports System.Xml.XPath

The imports are primarily per the default configuration for a Windows application; the System.Xml and System.Xml.XPath library import are the only departure from the default.

Following the imports, the class is declared and a constructor added. A local string variable it declared and used to hold the path to the XML document.

Public Class frmTest

 

    ' the document opened for examination

    Dim doc As New XmlDocument()

 

    ''' <summary>

    ''' Constructor

    '''

    ''' Uses the same xml document as is opened

    ''' in the main form of the application; this

    ''' is passed upon creating a new instance

    ''' of this test form

    '''

    ''' </summary>

    ''' <param name="filePath"></param>

    ''' <remarks></remarks>

    Public Sub New(ByVal filePath As String)

 

        InitializeComponent()

 

        ' Load the xml document for use in

        ' this form

        Try

 

            doc.Load(filePath)

            Me.Text = "Testing - " & filePath

 

        Catch ex As Exception

 

            MessageBox.Show(ex.Message, "Error Loading XML document")

 

        End Try

 

    End Sub

The next bit of code is the button click event handler for the test itself. This code uses the expression text box content as path; whatever is captured from the resulting query is displayed in the result section of the form. This is accomplished by creating an XPathNavigator and using the XML document's CreateNavigator method. Once the navigator is declared, we can send the expression search term directly to the navigator's select method to test it.
 

    ''' <summary>

    ''' Tests the statement entered into the expression

    ''' test box and display the results in the

    ''' results panel

    ''' </summary>

    ''' <param name="sender"></param>

    ''' <param name="e"></param>

    ''' <remarks></remarks>

    Private Sub btnTest_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnTest.Click

 

        rtbResults.Text = String.Empty

 

        ' get an xpath navigator  

        Dim navigator As XPathNavigator

        navigator = doc.CreateNavigator

 

        ' contain the results in a stringbuilder

        Dim sb As New StringBuilder() 

 

        Try

 

            ' look for the path and use an iterator to capture the results

            Dim nodes As XPathNodeIterator =

            navigator.Select(txtTestExpression.Text)

 

            While (nodes.MoveNext())

 

                Dim node As XPathNavigator = nodes.Current

 

                ' depending upon which radio button is checked,

                ' write the results to the string builder

                If optInnerXml.Checked = True Then

 

                    sb.Append(node.InnerXml & Environment.NewLine)

 

                ElseIf optOuterXml.Checked = True Then

 

                    sb.Append(node.OuterXml & Environment.NewLine)

 

                Else

 

                    sb.Append(node.Value & Environment.NewLine)

 

                End If

 

            End While 

 

        Catch ex As Exception

 

            MessageBox.Show(ex.Message, "XPath Error")

 

        End Try 

 

        ' post any results to the results box

        rtbResults.Text = sb.ToString()

 

    End Sub

The last bit of the class is used to close the form.
 

    ''' <summary>

    ''' Close this form

    ''' </summary>

    ''' <param name="sender"></param>

    ''' <param name="e"></param>

    ''' <remarks></remarks>

    Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click

 

        Me.Dispose()

 

    End Sub

The only remaining forms are used to display the help. The help file contains access to an RTF document which contains instructions and samples showing a few ways in which it is possible to use the utility.

Summary.

This application was provided as a starter utility application that may be used to evaluate paths when writing XPath based queries against an existing XML document. There are a lot of other things that one could add to the application to make it more useful; a better interface for defining and testing more elaborate queries would be a good enhancement.