Using CreateData() to Build a List of KinFolk Objects in VS .NET

Create Quick Response Code in VS .NET Using CreateData() to Build a List of KinFolk Objects

Public Function CreateData() As List(Of KinFolk) Dim nn As New List(Of KinFolk) nnAdd(New KinFolk With {FName = Dave , Father = Ron , Gender = m }) nnAdd(New KinFolk With {FName = Karen , Father = Ron , Gender = f }) nnAdd(New KinFolk With {FName = Amy , Father = Mike , Gender = f }) nnAdd(New KinFolk With {FName = Meghann , Father = Mike , Gender = f }) nnAdd(New KinFolk With {FName = Holly , Father = Mike , Gender = f }) nnAdd(New KinFolk With {FName = Kurtis , Father = Paul , Gender = m }) nnAdd(New KinFolk With {FName = Rachel , Father = Paul , Gender = f }) nnAdd(New KinFolk With {FName = Elaine , Father = Stan , Gender = f }) nnAdd(New KinFolk With {FName = Brenda , Father = Stan , Gender = f }) nnAdd(New KinFolk With {FName = Julie , Father = Stan , Gender = f }) nnAdd(New KinFolk With {FName = Jaclyn , Father = Stan , Gender = f }) Return nn End Function

LINQ to XML can generate a complete, well-formed XML file based on almost any data you provide In this example, you use the list of KinFolk objects from Listing 7-2 It could just as easily be rows of data from a database Follow these steps to read the data, build an XML document, and save the XML to a file: 1 In createxmlaspx (added in the preceding section), switch to Design view and double-click an empty area of the page to create an event handler for the Page Load event 2 Inside the Page_Load() subroutine, add the code in Listing 7-3 3 At the top of the source code, add the following directives: <%@ Import Namespace= SystemCollectionsGeneric %> <%@ Import Namespace= SystemXMLLinq %> 4 If your project doesn t already have an App_Data folder, create one (Right-click the project name and then choose Add ASPNET Folder App_Data)

5 Browse to createxmlaspx A new file named niecesandnephewsxml appears in the App_Data folder (You may need to refresh Solution Explorer to see the new file) Here s a sample of the XML file s contents: <kinfolk> <kin> <fname gender= m >Dave</fname> <father>Ron</father> </kin> </kinfolk>

Listing 7-3:

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Dim nn = CreateData() Dim kfdoc As New XDocument(New XDeclaration( 10 , Nothing, Nothing)) kfdocAdd(New XComment( LINQ to XML Generated File )) Dim kfrootelement As New XElement( kinfolk ) Dim kfitem As XElement Dim kffirstname As XElement Dim kffather As XElement Dim kfgender As XAttribute For Each n In nn kfitem = New XElement( kin ) kffirstname = New XElement( fname , nFName) kfgender = New XAttribute( gender , nGender) kffirstnameAdd(kfgender) kfitemAdd(kffirstname) kffather = New XElement( father , nFather) kfitemAdd(kffather) kfrootelementAdd(kfitem) Next kfdocAdd(kfrootelement) Try kfdocSave(ServerMapPath( ~/App_Data/niecesandnephewsxml )) Label1Text = File written Catch exc As Exception Label1Text = Problem: & excMessage End Try

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Here s how Listing 7-3 works:

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The CreateData() subroutine gets the data to use in the XML file The variable kfdoc holds a new XDocument object that includes an XML declaration created with an XDeclaration object The kfrootelement establishes the root node of the XML (which renders as <kinfolk> in the XML file) The Dim statements declare several variables as XElement types so they can be used in the For Each loop, where most of the work takes place

KinFolk objects as represented by variable nn On each pass through the loop, the code creates a <kin> element and adds an <fname> element with the value held in the FName property of the object Notice that using the XAttribute object creates a gender attribute that goes becomes part of the <fname> element by calling kffirstnameAdd()

After creating the <father> element and including its value from nFather, the entire node is added to the parent element, which in turn is added to the root element This part is wrapped in a TryCatchEnd Try sequence so the page doesn t crash if the ASPNET account doesn t have write permission in the destination folder