XML Pathfinder - A Visual Basic Utility

Scott Lysle
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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:

Copy only the text contained in the current node,
Copy the path to the node formatted as a query for that attribute value, and
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:

Solution Explorer-in-windows8.gif

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)

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)

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.