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:\Personal\family.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:\CMS\Personal\family.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