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  • [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

     1 Imports System.IO
     2 Imports System.Xml
     3 Module ParsingUsingXmlTextReader
     4 Sub Main()
     5   Dim m_xmlr As XmlTextReader
     6   'Create the XML Reader
     7   m_xmlr = New XmlTextReader("C:Personalfamily.xml")
     8   'Disable whitespace so that you don't have to read over whitespaces
     9   m_xmlr.WhiteSpaceHandling = WhiteSpaceHandling.NONE
    10   'read the xml declaration and advance to family tag
    11   m_xmlr.Read()
    12   'read the family tag
    13   m_xmlr.Read()
    14   'Load the Loop
    15   While Not m_xmlr.EOF
    16     'Go to the name tag
    17     m_xmlr.Read()
    18     'if not start element exit while loop
    19     If Not m_xmlr.IsStartElement() Then
    20       Exit While
    21     End If
    22     'Get the Gender Attribute Value
    23     Dim genderAttribute = m_xmlr.GetAttribute("gender")
    24     'Read elements firstname and lastname
    25     m_xmlr.Read()
    26     'Get the firstName Element Value
    27     Dim firstNameValue = m_xmlr.ReadElementString("firstname")
    28     'Get the lastName Element Value
    29     Dim lastNameValue = m_xmlr.ReadElementString("lastname")
    30     'Write Result to the Console
    31     Console.WriteLine("Gender: " & genderAttribute _
    32       & " FirstName: " & firstNameValue & " LastName: " _
    33       & lastNameValue)
    34     Console.Write(vbCrLf)
    35   End While
    36   'close the reader
    37   m_xmlr.Close()
    38 End Sub
    39 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

     1 Imports System.IO
     2 Imports System.Xml
     3 Module ParsingUsingXmlDocument
     4 Sub Main()
     5   Try
     6     Dim m_xmld As XmlDocument
     7     Dim m_nodelist As XmlNodeList
     8     Dim m_node As XmlNode
     9     'Create the XML Document
    10     m_xmld = New XmlDocument()
    11     'Load the Xml file
    12     m_xmld.Load("C:CMSPersonalfamily.xml")
    13     'Get the list of name nodes 
    14     m_nodelist = m_xmld.SelectNodes("/family/name")
    15     'Loop through the nodes
    16     For Each m_node In m_nodelist
    17       'Get the Gender Attribute Value
    18       Dim genderAttribute = m_node.Attributes.GetNamedItem("gender").Value
    19       'Get the firstName Element Value
    20       Dim firstNameValue = m_node.ChildNodes.Item(0).InnerText
    21       'Get the lastName Element Value
    22       Dim lastNameValue = m_node.ChildNodes.Item(1).InnerText
    23       'Write Result to the Console
    24       Console.Write("Gender: " & genderAttribute _
    25         & " FirstName: " & firstNameValue & " LastName: " _
    26         & lastNameValue)
    27       Console.Write(vbCrLf)
    28     Next
    29   Catch errorVariable As Exception
    30     'Error trapping
    31     Console.Write(errorVariable.ToString())
    32   End Try
    33 End Sub
    34 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

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  • 原文地址:https://www.cnblogs.com/masonlu/p/4711666.html
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