USING XML WITH VBNET
XML File Parsing in VB.NET - The Code Project - 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>Figure1: Xml file
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
CollapseImports 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 ModuleFigure 2: Xml Parsing with XmlTextReader
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
CollapseImports 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(0).InnerText
'Get the lastName Element Value
Dim lastNameValue = m_node.ChildNodes.Item(1).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 ModuleFigure 3: Xml Parsing with XmlDocument
Compilation and Result
Make sure you have vbc.exe in your path. From the command prompt go to C:\Personal>. Compile ParsingUsingXmlTextReader.vb and ParsingUsingXmlDocument.vb.
C:\Personal>vbc /out:ParsingUsingXmlTextReadervb.exe ParsingUsingXmlTextReader.vb
C:\Personal>vbc /out:ParsingUsingXmlDocumentvb.exe ParsingUsingXmlDocument.vbWhen you run the individual program
C:\Personal>ParsingUsingXmlTextReadervb.exe OR
C:\Personal>ParsingUsingXmlDocumentvb.exeYou will see the following result for both
Gender: Male FirstName: Tom LastName: Smith
Gender: Female FirstName: Dale LastName: SmithConclusion
There are different ways to parse XML files and the best method depends on your situation and the programming style preferred.
then using datasetUsing DataSet is simple..
In the code behind add the following lines.
Dim myDataSet as New DataSet()
myDataSet.ReadXml(Server.MapPath("xmlfilename.xml"))
datagrid1.DataSource = myDataSet
datagrid1.DataBind()
In the aspx page add the following..
<asp:datagrid id="datagrid1" runat="server"
AutoGenerateColumns="False"
Font-Name="Verdana"
Font-Size="Small"
HorizontalAlign="Center">
<Columns>
<asp:BoundColumn HeaderText="First Name" DataField="firstname" />
<asp:BoundColumn HeaderText="Last Name" DataField="lastname" />
</Columns>
</asp:datagrid>
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