A VB.NET XML Retrieval Class

Category:

C#, VB.NET, ASP.NET

Type:

Classes

Difficulty:

Intermediate

Author: Anonymous

Version Compatibility: Visual Basic.NET

More information:

This class and sample test file can be used to get XML data into your program. It is simple and works. A basic test program called testXMLSimple is included in the source.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
' (None)

Code:

Imports System.IO
Imports System.Xml

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' XMLSimple: 
'
' Author....: Zachary Lewis
' Email.....: freeware@zcstr.com
'
' Disclaimer: Use this DEMO code entirely at your own risk
'             and accept all responsibility for your actions.
'
' Freeware..: Cost is Free
'
' Purpose...: This class XMLSimple Supports simple XML Element retreival.
'

Public Class XMLFile

Private myXMLFileName As String
    Private myXMLReader As XmlTextReader
    Public hasErrors As Boolean
    Public lastErrorMessage As String

Private isInitialized as boolean

'
    ' Internal reset of XML file Stream
    '
    Private Sub resetXMLFile()
        Dim tmpTextStream As StreamReader
        Dim returnResult As Boolean

returnResult = False

Try
            '
            ' My Warm in fuzz.  Not about performance, simple.
            myXMLReader = Nothing
            System.GC.Collect()

tmpTextStream = New StreamReader(myXMLFileName)
            myXMLReader = New XmlTextReader(tmpTextStream)

myXMLFileName = myXMLFileName
            returnResult = True

Catch exIO As FileNotFoundException

' Handle File not Found issue here
            ' find Message in message file based on locale
            ' 
            lastErrorMessage = exIO.ToString
            hasErrors = True

Catch exXML As XmlException
            '
            ' Handle XML issue here

lastErrorMessage = exXML.ToString
            hasErrors = True

Catch ex As Exception
            '            '
            '

lastErrorMessage = ex.ToString
            hasErrors = True

End Try

End Sub

'
' Initialize the XML File that you will be using
'
    Public Function setXMLFile(ByVal pFileName As String) As Boolean

Dim myTextStream As StreamReader
        Dim returnResult As Boolean

returnResult = False

Try
            myTextStream = New StreamReader(pFileName)
            myXMLReader = New XmlTextReader(myTextStream)

myXMLFileName = pFileName
            returnResult = True
            isInitialized = True

Catch exIO As FileNotFoundException

' Handle File not Found issue here
            ' find Message in message file based on locale
            '

lastErrorMessage = exIO.ToString
            hasErrors = True

Catch exXML As XmlException
            '
            ' Handle XML issue here

lastErrorMessage = exXML.ToString
            hasErrors = True

Catch ex As Exception
            '            '
            '

lastErrorMessage = ex.ToString
            hasErrors = True

End Try

Return returnResult

End Function

Public Function getAllElementValues(ByVal pElementName As String, ByVal pIndex As Integer, ByVal pDepth As Integer) As String

Dim tmpStr As String
        Dim hasFoundElement As Boolean
        Dim tmpIndex As Integer
        Dim resultValue As String
        If Not Me.isInitialized Then
            hasErrors = True
            Me.lastErrorMessage = "Please call setXMLFile to intialize the XML file name."

resultValue = Nothing
            Exit Function

End If

hasFoundElement = False

Try

tmpIndex = 0
            myXMLReader.Read()
            While Not myXMLReader.EOF And Not hasFoundElement

If myXMLReader.NodeType = XmlNodeType.Element Then

If myXMLReader.Name = pElementName And _
                         myXMLReader.Depth = pDepth _
                    Then

tmpIndex = tmpIndex + 1
                        If tmpIndex = pIndex Then
                            resultValue = myXMLReader.ReadElementString
                            hasFoundElement = True
                        End If

End If

If myXMLReader.EOF Then
                    '
                    ' do any cleanup
                Else

' read next
                    myXMLReader.Read()

End If

End While

Catch ex As Exception

lastErrorMessage = ex.ToString
            hasErrors = True

End Try

resetXMLFile()

Return resultValue

End Function
    Public Function getAllElementValues(ByVal pElementName As String, ByVal pDepth As Integer) As Collection
        Dim resultValue As Collection

If Not Me.isInitialized Then
            hasErrors = True
            Me.lastErrorMessage = "Please call setXMLFile to intialize the XML file name."

resultValue = Nothing
            Exit Function

End If
        Try

myXMLReader.Read()
            While Not myXMLReader.EOF
                If myXMLReader.NodeType = XmlNodeType.Element Then

If myXMLReader.Name = pElementName And _
                         myXMLReader.Depth = pDepth _
                    Then

If resultValue Is Nothing Then
                            resultValue = New Collection
                        End If
                        resultValue.Add(myXMLReader.ReadElementString)

End If

If myXMLReader.EOF Then
                    '
                    ' do any cleanup
                Else

' read next
                    myXMLReader.Read()

End If

End While

Catch ex As Exception

lastErrorMessage = ex.ToString
            hasErrors = True

End Try
        resetXMLFile()
        Return resultValue

End Function

Public Function getElementValue(ByVal pElementName As String, ByVal pIndex As Integer, ByVal pDepth As Integer) As String

Dim tmpStr As String
        Dim hasFoundElement As Boolean
        Dim tmpIndex As Integer
        Dim resultValue As String

If Not Me.isInitialized Then
            hasErrors = True
            Me.lastErrorMessage = "Please call setXMLFile to intialize the XML file name."

resultValue = Nothing
            Exit Function

End If
        hasFoundElement = False

Try

tmpIndex = 0
            myXMLReader.Read()
            While Not myXMLReader.EOF And Not hasFoundElement

If myXMLReader.NodeType = XmlNodeType.Element Then

If myXMLReader.Name = pElementName And _
                         myXMLReader.Depth = pDepth _
                    Then

End If

If myXMLReader.EOF Then
                    '
                    ' do any cleanup future

Else

' read next XML Line 
                    myXMLReader.Read()

End If

End While

Catch ex As Exception

lastErrorMessage = ex.ToString
            hasErrors = True

End Try

resetXMLFile()

Return resultValue

End Function

'
    ' Returns a collection of hashtables matching the requested Node Element Names and Depth
    '
    Public Function getAllElementValues(ByVal pElementNames As Collection) As Collection
        Dim resultValue As Collection
        Dim tmpElementList As Collection

Dim tmpResultHashTable As Hashtable

Try

myXMLReader.Read()
            While Not myXMLReader.EOF
               
                   
                If myXMLReader.NodeType = XmlNodeType.Element Then

For Each tmpStr As String In pElementNames

If myXMLReader.Name = tmpStr _
                        Then
                            If resultValue Is Nothing Then
                                resultValue = New Collection
                            End If

Dim tmpStr2 As String
                            tmpStr2 = myXMLReader.ReadElementString

If tmpResultHashTable Is Nothing Then

tmpElementList = New Collection
                                tmpResultHashTable = New Hashtable

tmpElementList.Add(tmpStr2)

tmpResultHashTable.Add(tmpStr, tmpElementList)
                                resultValue.Add(tmpResultHashTable)

Else

tmpElementList = tmpResultHashTable(tmpStr)
                                If tmpElementList Is Nothing Then
                                    tmpElementList = New Collection
                                    tmpElementList.Add(tmpStr2)

Else

tmpElementList.Add(tmpStr2)

End If

'
                                ' Must be a better way to update a Hashtable
                                '
                                If tmpResultHashTable(tmpStr) Is Nothing Then

tmpResultHashTable.Add(tmpStr, tmpElementList)

Else

tmpResultHashTable.Remove(tmpStr)
                                    tmpResultHashTable.Add(tmpStr, tmpElementList)

End If

resultValue.Add(tmpResultHashTable.Clone)

tmpResultHashTable.Clear()
                                tmpElementList = Nothing

End If

End If
                    Next

End If

If myXMLReader.EOF Then
                    '
                    ' do any cleanup
                Else

' read next
                    myXMLReader.Read()

End If

End While

Catch ex As Exception

lastErrorMessage = ex.ToString
            hasErrors = True

End Try
        resetXMLFile()
        Return resultValue

End Function

End Class