CODEWITHSUNDEEP
asp.netvb.nettreeviewnodes
Emad-ud-deen
Emad-ud-deen

Reputation: 4864

Event handler to use when nodes of ASP.Net TreeView are clicked by user

Using the following web.sitemap as an example, we would like to create an event handler to catch when the user clicks on the "Teachers" link of an ASP.Net TreeView. This happens to be a parent node.

  <siteMapNode title="Teachers" url="~/DefaultTeachers.aspx" >
    <siteMapNode url="~/Teachers.aspx" title="Teachers" description="Maintain details of each Teacher." />
    <siteMapNode url="~/TeacherSchedules.aspx" title="Teacher Schedules" description="Maintain teacher schedules." />
    <siteMapNode url="~/TeacherEmailNotices.aspx" title="Email Notices To Teachers" description="Email notices to teachers." />
  </siteMapNode>

Can you tell me what event to place in the markup of the ASP.Net TreeView maybe something like this?

<asp:TreeView 
    id="TreeViewMain"
    runat="server"
    ExpandDepth="0"
    OnUserClickedTheLink="TreeViewMain_UserClickedTheLink"
    DataSourceID="KnowledgeAcademySiteMap">

    <RootNodeStyle ImageUrl="/Images/book.png" />
    <ParentNodeStyle ImageUrl="/Images/book.png" />
    <LeafNodeStyle ImageUrl="/Images/book.png" />
</asp:TreeView>

Also in the code-behind file we would like to place e.Node or something like that in an "If" statement to test what node was actually clicked:

If e.Node.Text = "Teachers" Then

    ' We will close all other nodes and open up the 3 leaf nodes under "Teachers" here.
    '----------------------------------------------------------------------------------
End If

Upvotes: 0

Views: 1836

Answers (1)

Denys Wessels
Denys Wessels

Reputation: 17039

The problem is that the TreeView can perform only one of two functions, which are:

  1. Post back
  2. Navigate

Since you're setting the tree view data source to a site map it will perform the Navigate function and will not fire any post back event. It will simply say - oh you cliked on the Teachers node I'm just going to take you to the Teachers page and nothing more.

There's a number of things you can try:

  1. Handle the processing inside the Load event of the teachers page. When this event fires it obviously means that the Teachers page is being loaded at which point you can write the code to expand and collapse certain tree view items.
  2. Another option is to get rid of the sitemap and use an XmlDataSource which maps to a custom xml file, this way your tree view will have the Post back behavior and you will be able to check every clicked node in the OnSelectedNodeChanged event:

Sample xml file:

<menu name="menu">
  <teachers name="teachers">
    <teacher name="teacher1" />
    <teacher name="teacher2" />
    <teacher name="teacher3" />
  </teachers>
</menu>

Code behind:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not Page.IsPostBack Then
        Dim ds As XmlDataSource = New XmlDataSource
        ds.DataFile = Server.MapPath("~/App_Data/menu.xml")
        TreeViewMain.DataSource = ds
        TreeViewMain.DataBind()
    End If
End Sub

Protected Sub SelectionChanged(sender As Object, e As EventArgs) Handles TreeViewMain.SelectedNodeChanged
    Dim selected As String = TreeViewMain.SelectedValue
    If selected.Equals("teachers") Then
        'Do any required processing and then manually redirect to the Teachers Page
    End If
End Sub

The problem with this approach of course is that you'll need to check every clicked item and manually redirect the user to a particular page which won't be acceptable if you have many tree view items to evaluate

Upvotes: 1

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