How To Select a Single Node in an XML Document from a TreeView in Visual Basic (252514)


The information in this article applies to:

  • Microsoft XML 2.0
  • Microsoft XML 3.0
  • Microsoft XML 4.0
  • Microsoft Visual Basic Enterprise Edition for Windows 6.0
  • ActiveX Data Objects (ADO) 2.1
  • ActiveX Data Objects (ADO) 2.5
  • ActiveX Data Objects (ADO) 2.6
This article was previously published under Q252514

SUMMARY

One of the methods added to the IDOMNode object in the IXMLDOMNode interface in Microsoft Internet Explorer 5 (IE5) is the SelectSingleNode method. This method applies a specified pattern-matching operation to a node's context and returns the first matching node. This behavior is similar to the SelectNode method, which returns a list of matching nodes.

MORE INFORMATION

The following sample demonstrates one implementation of this method. This sample opens an ADO Recordset and saves the data to an XML Document file using the FileSystemObject. This XML file is subsequently opened, and a Visual Basic TreeView control is filled with its data. Subsequently, the SelectSingleNode method is implemented to select a single node in the XML Document based on an item chosen from the TreeView control.

If a newer version of MSXML has been installed in side-by-side mode, you must explicitly use the Globally Unique Identifiers (GUIDs) or ProgIDs for that version to run the sample code. For example, MSXML version 4.0 can only be installed in side-by-side mode. For additional information about the code changes that are required to run the sample code with the MSXML 4.0 parser, click the following article number to view the article in the Microsoft Knowledge Base:

305019 INFO: MSXML 4.0 Specific GUIDs and ProgIds

NOTE: The $ieq$ syntax is used here for pattern matching against a Node Element. However, the "@" syntax can be used for Attribute pattern matching.
  1. To run this sample, start a new Visual Basic Standard Exe project. Form1 is created by default.
  2. On the Project menu, under References, select the following items: Microsoft ActiveX Data Objects Library
    Microsoft XML, Version 1.0 or later
    Microsoft Scripting Runtime*
    *The FileSystemObject Object Model is contained in the Microsoft Scripting Runtime Library.

  3. From the Project menu, add a standard Module and copy the following code to create the appropriate variables needed in the project:
    Option Explicit

Public cn As New adodb.Connection
Public rs As New adodb.Recordset
Public myI As Integer
Public StrTmp As String
Public Errs1 As Errors
Public myFSO As New FileSystemObject
Public myTxtStream As TextStream
Public myfld As adodb.Field
Public domdoc As New MSXML.DOMDocument

To specify a specific version, use a declaration like the following, with the appropriate version in the ProgID:
Public domdoc As New MSXML2.DOMDocument40
  4. Draw the following controls on Form1 and set their Properties as listed below:
    Control		        Name			Caption
Command Button	        cmdOpenRS               Open ADO Recordset
Command Button	        cmdSaveRSasXML          Save RS as XML using FSO
Command Button	        cmdPopulateTview        Populate TreeView
Command Button	        cmdExit                 Exit
Label		        lblNodeSelected         Node Selected:
Text BoX                txtNodeSelected
TreeView Control*       xtvFSO
*The TreeView Control is part of the Windows Common Controls.
Therefore, you'll want to check this off in your Project-Components list.
  5. Copy the following code into the General Declarations section of the code window:NOTE: Replace your Server Name, User ID, and Password information in the Connection String. 
    Option Explicit

Private Sub cmdOpenRS_Click()
On Error GoTo AdoError

Screen.MousePointer = vbHourglass

'Check to be sure the connection is not already opened:
If cn.State = 1 Then
    cn.Close
    Set cn = Nothing
End If

cn.Open "driver={SQL Server};Server=YourServer; " & _
"uid=YourUID;pwd=YourPWD;database=Northwind"

'Check to be sure a Recordset is not already opened:
If rs.State = 1 Then
    rs.Close
    Set rs = Nothing
End If

With rs
    .CursorLocation = adUseClient
    .CursorType = adOpenStatic
    .LockType = adLockOptimistic
    .CacheSize = 50
    .Source = "Select CustomerID, " & _
    "CompanyName, ContactName, Region from Customers"
    .ActiveConnection = cn
    .Open
End With

rs.MoveLast
rs.MoveFirst

'txtFsoRecordCount.Text = rs.RecordCount
MsgBox "There are " & rs.RecordCount & " Records in RS"

Screen.MousePointer = vbNormal

Exit Sub

AdoError:

Dim errLoop As Error
Dim strError As String

myI = 1

StrTmp = StrTmp & vbCrLf & "VB Error # " & Str(Err.Number)
StrTmp = StrTmp & vbCrLf & "   Generated by " & Err.Source
StrTmp = StrTmp & vbCrLf & "   Description  " & Err.Description

' Display Error Information for each Error object.
Set Errs1 = cn.Errors
For Each errLoop In Errs1
    With errLoop
        StrTmp = StrTmp & vbCrLf & "Error #" & myI & ":"
        StrTmp = StrTmp & vbCrLf & "   ADO Error   #" & .Number
        StrTmp = StrTmp & vbCrLf & "   Description  " & .Description
        StrTmp = StrTmp & vbCrLf & "   Source       " & .Source
        myI = myI + 1
    End With
Next

MsgBox StrTmp

End Sub

Private Sub cmdExit_Click()
If cn.State = 1 Then
    cn.Close
    Set cn = Nothing
End If

If rs.State = 1 Then
    rs.Close
    Set rs = Nothing
End If

Unload Me

End Sub

Private Sub cmdSaveRSasXML_Click()
Screen.MousePointer = vbHourglass

'If the file already exists, first Kill it.
'then create it:
'If it does not already exist, simply create it:
On Error GoTo mdkNoSeeEm
Const mdkNoSeeEm = 53 'File Not Found
Kill "Customers.xml"

'Create a Text file using the FileSystemObject:

Set myTxtStream = myFSO.CreateTextFile(App.Path & "\Customers.xml", 

True, True)

'Write data to the Text File to compile
'the XML Document using the TextStream:

myTxtStream.WriteLine "<?xml version=""1.0"" standalone=""yes""?>"
myTxtStream.WriteLine "<Customers>"
rs.MoveFirst

    Do While Not rs.EOF
myTxtStream.WriteLine "<Customer>"
myTxtStream.WriteLine "<CustomerID>" & 

ReplaceEntXMLSpecChar(rs.Fields("CustomerID") & "", "&", "amp;") & 

"</CustomerID>"
myTxtStream.WriteLine "<CompanyName>" & 

ReplaceEntXMLSpecChar(rs.Fields("CompanyName") & "", "&", "amp;") & 

"</CompanyName>"
myTxtStream.WriteLine "<ContactName>" & 

ReplaceEntXMLSpecChar(rs.Fields("ContactName") & "", "&", "amp;") & 

"</ContactName>"
myTxtStream.WriteLine "<Region>" & 

ReplaceEntXMLSpecChar(rs.Fields("Region") & "", "&", "amp;") & 

"</Region>"
myTxtStream.WriteLine "</Customer>"
rs.MoveNext
Loop
rs.MoveFirst

myTxtStream.WriteLine "</Customers>"

myTxtStream.Close

Screen.MousePointer = vbNormal

Exit Sub

mdkNoSeeEm:
    If Err.Number = mdkNoSeeEm Then
        Resume Next
    End If
    
Screen.MousePointer = vbNormal

End Sub

Private Function ReplaceEntXMLSpecChar(ByVal strSource As String, ByVal 

strSearchFor As String, ByVal strReplace As String) As String
    Dim lngPointer As Long, strNew As String
    lngPointer = InStr(strSource, strSearchFor)
    If lngPointer = 0 Then
        ReplaceEntXMLSpecChar = strSource
    Else
        strNew = Left$(strSource, lngPointer - 1) & strReplace & 

Mid(strSource, lngPointer + 1, Len(strSource))
        ReplaceEntXMLSpecChar = strNew
    End If
End Function

Private Sub cmdPopulateTview_Click()
On Error GoTo MyXMLPerr

'Fill The TreeView with data from the XML Document:

With domdoc
    .async = False
    .Load App.Path & "\customers.xml"
End With

If domdoc.readyState = 4 Then
    xtvFSO.Nodes.Clear
    AddNode domdoc.documentElement
End If

Exit Sub

MyXMLPerr:
    MsgBox domdoc.parseError.reason & vbCrLf & " Line Number In 

Document: " & domdoc.parseError.Line & vbCrLf & 

domdoc.parseError.srcText
End Sub

Private Sub xtvFSO_DblClick()

Dim mytempTVnode As String
Dim SelectedNode As IXMLDOMNode

mytempTVnode = xtvFSO.SelectedItem
Set SelectedNode = 

domdoc.documentElement.SelectSingleNode("//Customers/Customer[CustomerI

D $ieq$ '" & mytempTVnode & "']")
txtNodeSelected.Text = SelectedNode.childNodes(2).Text
End Sub<BR/>
<BR/>
Private Sub AddNode(ByRef myNode As IXMLDOMNode, Optional ByRef TreeNode As Node)

Dim tvcusterrNode As Node
Dim tvcusterrNodeList As IXMLDOMNodeList
Dim i As Long
             
    If TreeNode Is Nothing Then
        Set tvcusterrNode = xtvFSO.Nodes.Add
    Else
        Set tvcusterrNode = xtvFSO.Nodes.Add(TreeNode, tvwChild)
    End If
       
    tvcusterrNode.Expanded = True
    tvcusterrNode.Text = myNode.nodeName
       
    If tvcusterrNode.Text = "#text" Then
           tvcusterrNode.Text = myNode.nodeTypedValue
    Else
           tvcusterrNode.Text = "<" & tvcusterrNode.Text & ">"
    End If

    Set tvcusterrNodeList = myNode.childNodes
    For i = 0 To tvcusterrNodeList.length - 1
        AddNode tvcusterrNodeList.Item(i), tvcusterrNode
    Next
End Sub
  6. Run the project.
  7. Click the Open ADO Recordset Commandbutton to open a Connection and Recordset, displaying the RecordCount Property.
  8. Click the Save RS as XML Commandbutton to create the XML Document file.
  9. Click the Populate TreeView Commandbutton to fill the TreeView control.
  10. Double-click on any Customer ID in the TreeView, and note that the Contact Name for that Customer ID is displayed in the Text Box.
Modification Type:MinorLast Reviewed:7/13/2004
Keywords:kbhowto KB252514
©2004 Microsoft Corporation. All rights reserved.