How to use the TreeNode object in selection mode in ASP.NET in VB.NET

You can use TreeNode in one of two modes:

– In selection mode, clicking the node posts back the page and raises the TreeView.SelectedNodeChanged event. This is default mode for all nodes.

– In navigation mode, clicking a node navigates to a new page, and the SelectedNodeChanged event is not raised. You place the TreeNode in navigation mode by setting the NavigateUrl property to anything other than an empty string.

The next example illustrates how you can use the TreeNode in selection mode. In the example as a source of data for the TreeView control an xml file named BooksList.xml which is placed in the folder App_Data is used.

 

Xml file BooksList.xml

 

<?xml version=”1.0″ encoding=”utf-8″?>

<BooksList>

<Book ISBN-13=”978-0545139700″>

<Title>Harry Potter and the Deathly Hallows</Title>

<Author>J.K. Rowling</Author>

<Price>14.99</Price>

<Available>True</Available>

<AdditionalInfo>

<Pages>784</Pages>

<Publisher>Arthur A. Levine Books</Publisher>

<Date>July 7, 2009</Date>

</AdditionalInfo>

</Book>

<Book ISBN-13=”978-1451648539″>

<Title>Steve Jobs</Title>

<Author>Walter Isaacson</Author>

<Price>14.88</Price>

<Available>True</Available>

<AdditionalInfo>

<Pages>656</Pages>

<Publisher>Simon and Schuster</Publisher>

<Date>October 24, 2011</Date>

</AdditionalInfo>

</Book>

<Book ISBN-13=”978-0765309761″>

<Title>Tunnel Vision</Title>

<Author>Gary Braver</Author>

<Price>14.15</Price>

<Available>False</Available>

<AdditionalInfo>

<Pages>383</Pages>

<Publisher>Forge</Publisher>

<Date>June 21, 2011</Date>

</AdditionalInfo>

</Book>

</BooksList>

 

File TreeViewTest.aspx

<body>

<form id=”form1″ runat=”server”>

<div>

<asp:Label ID=”LblInfo” runat=”server” Text=””></asp:Label>

<asp:TreeView ID=”TreeView1″ runat=”server”

onselectednodechanged=”TreeView1_SelectedNodeChanged”>

</asp:TreeView>

</div>

</form>

</body>

In the example TreeNode structure is created by hand:

 

File TreeViewTest.aspx.vb

 

Imports System.Collections.Generic

Imports System.Linq

Imports System.Web

Imports System.Web.UI

Imports System.Web.UI.WebControls

Imports System.Data

Imports System.IO

 

Namespace TreeViewVB

Public Partial Class TreeViewTest

Inherits System.Web.UI.Page

Protected Sub Page_Load(sender As Object, e As EventArgs)

 

If Not Page.IsPostBack Then

‘ Fill a DataSet with two DataTable objects, representing

‘ the Books and Additional Info tables.

Dim file As String = Path.Combine(Request.PhysicalApplicationPath, “App_Data\BooksList.xml”)

Dim fs As New FileStream(file, FileMode.Open)

Dim ds As New DataSet()

ds.ReadXml(fs)

 

‘ Loop through the books records.

For Each row As DataRow In ds.Tables(“Book”).Rows

‘ Use the constructor that requires just text

‘ and a nondisplayed value.

Dim nodeBook As New TreeNode(“ISBN-13:” & row(“ISBN-13”).ToString(), row(“ISBN-13”).ToString())

Dim nodeTitle As New TreeNode(“Title: ” & row(“Title”).ToString())

Dim nodeAuthor As New TreeNode(“Author: ” & row(“Author”).ToString())

Dim nodeAddInfo As New TreeNode(“Additional info”)

nodeBook.ChildNodes.Add(nodeTitle)

nodeBook.ChildNodes.Add(nodeAuthor)

nodeBook.ChildNodes.Add(nodeAddInfo)

TreeView1.Nodes.Add(nodeBook)

 

‘ Get the children (additional information) for this parent (book).

Dim childRows As DataRow() = row.GetChildRows(ds.Relations(0))

 

‘ Loop through all information about this book.

For Each childRow As DataRow In childRows

Dim nodePublisher As New TreeNode(“Publisher: ” & childRow(“Publisher”).ToString())

Dim nodePages As New TreeNode(“Pages: ” & childRow(“Pages”).ToString())

nodeAddInfo.ChildNodes.Add(nodePublisher)

nodeAddInfo.ChildNodes.Add(nodePages)

Next

 

‘ Keep all books collapsed (initially).

nodeBook.Collapse()

Next

End If

End Sub

 

Protected Sub TreeView1_SelectedNodeChanged(sender As Object, e As EventArgs)

If TreeView1.SelectedNode Is Nothing Then

Return

End If

If TreeView1.SelectedNode.Depth = 0 Then

LblInfo.Text = “You selected Book ID: “

ElseIf TreeView1.SelectedNode.Depth = 1 Then

LblInfo.Text = “You selected Additional info ID: “

End If

LblInfo.Text += TreeView1.SelectedNode.Value

End Sub

End Class

End Namespace

The next picture presents the results:

 

Filling a TreeView with data from XML file in VB.NET

Filling a TreeView with data from XML file in VB.NET