IntroductionParsingxmlfiles has always been time consuming and sometimes tricky. .NET frameworkPRovides powerful new ways of parsing XML. The various techniques know to parse xml files with .NET framework are usingXmlTextReader,XmlDocument,XmlSerializer,DataSetandXpathDocument. I will explore theXmlTextReaderandXmlDocumentapproach here.
The Xml FileFigure 1 outlines the xml file that will be parsed.
<?xml version="1.0" encoding="UTF-8"?><family><namegender="Male"><firstname>Tom</firstname><lastname>Smith</lastname></name><namegender="Female"><firstname>Dale</firstname><lastname>Smith</lastname></name></family>
Parsing XML with XMLTextReaderUsingXmlTextReaderis appropriate when the structure of the XML file is relatively simple. Parsing withXmlTextReadergives you a pre .net feel as you sequentially walk through the file usingRead()and get data usingGetAttribute()andReadElementString()methods. Thus while usingXmlTextReaderit is up to the developer to keep track where he is in the Xml file andRead()correctly. Figure 2 below outlines parsing of xml file withXmlTextReader
1ImportsSystem.IO2ImportsSystem.Xml3ModuleParsingUsingXmlTextReader4SubMain()5Dimm_xmlrAsXmlTextReader6'Create the XML Reader7m_xmlr =NewXmlTextReader("C:\Personal\family.xml")8'Disable whitespace so that you don't have to read over whitespaces9m_xmlr.WhiteSpaceHandling =WhiteSpaceHandling.NONE10'read the xml declaration and advance to family tag11m_xmlr.Read()12'read the family tag13m_xmlr.Read()14'Load the Loop15WhileNotm_xmlr.EOF16'Go to the name tag17m_xmlr.Read()18'if not start element exit while loop19IfNotm_xmlr.IsStartElement()Then20ExitWhile21EndIf22'Get the Gender Attribute Value23DimgenderAttribute = m_xmlr.GetAttribute("gender")24'Read elements firstname and lastname25m_xmlr.Read()26'Get the firstName Element Value27DimfirstNameValue = m_xmlr.ReadElementString("firstname")28'Get the lastName Element Value29DimlastNameValue = m_xmlr.ReadElementString("lastname")30'Write Result to the Console31Console.WriteLine("Gender:"&genderAttribute _32&"FirstName:"& firstNameValue &"LastName:"_33&lastNameValue)34Console.Write(vbCrLf)35EndWhile36'close the reader37m_xmlr.Close()38End Sub39End Module
Parsing XML with XmlDocumentTheXmlDocumentclass is modeled based on Document Object Model.XmlDocumentclass is appropriate if you need to extract data in a non-sequential manner. Figure 3 below outlines parsing of xml file withXmlDocument
1ImportsSystem.IO2ImportsSystem.Xml3ModuleParsingUsingXmlDocument4SubMain()5Try6Dimm_xmldAsXmlDocument7Dimm_nodelistAsXmlNodeList8Dimm_nodeAsXmlNode9'Create the XML Document10m_xmld =NewXmlDocument()11'Load the Xml file12m_xmld.Load("C:\CMS\Personal\family.xml")13'Get the list of name nodes14m_nodelist = m_xmld.SelectNodes("/family/name")15'Loop through the nodes16ForEachm_nodeInm_nodelist17'Get the Gender Attribute Value18DimgenderAttribute = m_node.Attributes.GetNamedItem("gender").Value19'Get the firstName Element Value20DimfirstNameValue = m_node.ChildNodes.Item(0).InnerText21'Get the lastName Element Value22DimlastNameValue = m_node.ChildNodes.Item(1).InnerText23'Write Result to the Console24Console.Write("Gender:"&genderAttribute _25&"FirstName:"& firstNameValue &"LastName:"_26&lastNameValue)27Console.Write(vbCrLf)28Next29CatcherrorVariableAsException30'Error trapping31Console.Write(errorVariable.ToString())32EndTry33End Sub34End 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