[vb.net]XML File Parsing in VB.NET

Introduction

Parsing XML files has always been time consuming and sometimes tricky. .NET framework provides powerful new ways of parsing XML. The various techniques know to parse xml files with .NET framework are using XmlTextReader, XmlDocument, XmlSerializer, DataSet and XpathDocument. I will explore the XmlTextReader and XmlDocument approach here.

The Xml File

Figure 1 outlines the xml file that will be parsed.

<?xml version="1.0" encoding="UTF-8"?>

<family>

  <name gender="Male">

    <firstname>Tom</firstname>

    <lastname>Smith</lastname>

  </name>

  <name gender="Female">

    <firstname>Dale</firstname>

    <lastname>Smith</lastname>

  </name>

</family>

Parsing XML with XMLTextReader

Using XmlTextReader is appropriate when the structure of the XML file is relatively simple. Parsing with XmlTextReader gives you a pre .net feel as you sequentially walk through the file using Read() and get data using GetAttribute() andReadElementString() methods. Thus while using XmlTextReader it is up to the developer to keep track where he is in the Xml file and Read() correctly. Figure 2 below outlines parsing of xml file with XmlTextReader

 Imports System.IO

 Imports System.Xml

 Module ParsingUsingXmlTextReader

 Sub Main()

   Dim m_xmlr As XmlTextReader

   'Create the XML Reader

   m_xmlr = New XmlTextReader("C:\Personal\family.xml")

   'Disable whitespace so that you don't have to read over whitespaces

   m_xmlr.WhiteSpaceHandling = WhiteSpaceHandling.NONE

   'read the xml declaration and advance to family tag

   m_xmlr.Read()

   'read the family tag

   m_xmlr.Read()

   'Load the Loop

   While Not m_xmlr.EOF

     'Go to the name tag

     m_xmlr.Read()

     'if not start element exit while loop

     If Not m_xmlr.IsStartElement() Then

       Exit While

     End If

     'Get the Gender Attribute Value

     Dim genderAttribute = m_xmlr.GetAttribute("gender")

     'Read elements firstname and lastname

     m_xmlr.Read()

     'Get the firstName Element Value

     Dim firstNameValue = m_xmlr.ReadElementString("firstname")

     'Get the lastName Element Value

     Dim lastNameValue = m_xmlr.ReadElementString("lastname")

     'Write Result to the Console

     Console.WriteLine("Gender: " & genderAttribute _

       & " FirstName: " & firstNameValue & " LastName: " _

       & lastNameValue)

     Console.Write(vbCrLf)

   End While

   'close the reader

   m_xmlr.Close()

 End Sub

 End Module

Parsing XML with XmlDocument

The XmlDocument class is modeled based on Document Object Model. XmlDocument class is appropriate if you need to extract data in a non-sequential manner. Figure 3 below outlines parsing of xml file with XmlDocument

 Imports System.IO

 Imports System.Xml

 Module ParsingUsingXmlDocument

 Sub Main()

   Try

     Dim m_xmld As XmlDocument

     Dim m_nodelist As XmlNodeList

     Dim m_node As XmlNode

     'Create the XML Document

     m_xmld = New XmlDocument()

     'Load the Xml file

     m_xmld.Load("C:\CMS\Personal\family.xml")

     'Get the list of name nodes

     m_nodelist = m_xmld.SelectNodes("/family/name")

     'Loop through the nodes

     For Each m_node In m_nodelist

       'Get the Gender Attribute Value

       Dim genderAttribute = m_node.Attributes.GetNamedItem("gender").Value

       'Get the firstName Element Value

       Dim firstNameValue = m_node.ChildNodes.Item().InnerText

       'Get the lastName Element Value

       Dim lastNameValue = m_node.ChildNodes.Item().InnerText

       'Write Result to the Console

       Console.Write("Gender: " & genderAttribute _

         & " FirstName: " & firstNameValue & " LastName: " _

         & lastNameValue)

       Console.Write(vbCrLf)

     Next

   Catch errorVariable As Exception

     'Error trapping

     Console.Write(errorVariable.ToString())

   End Try

 End Sub

 End Module

You will see the following result for both

Gender: Male FirstName: Tom LastName: Smith

Gender: Female FirstName: Dale LastName: Smith

http://www.codeproject.com/Articles/4826/XML-File-Parsing-in-VB-NET

巴特西

[vb.net]XML File Parsing in VB.NET

Introduction

The Xml File

Parsing XML with XMLTextReader

Parsing XML with XmlDocument

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