CODEWITHSUNDEEP
asp.netvb.nettreeviewcode-behindexpand
Emad-ud-deen
Emad-ud-deen

Reputation: 4864

Expanding an ASP.Net TreeView node from code-behind

I'm learning how to access the controls of an ASP.Net master page and trying to expand a particular TreeView node. I'm doing this from another page that is not a master page.

objContentPlaceHolder, objLoginView and objTreeView all have a value as confirmed by using the debugger.

Can you look at this code and let us know why the code in the for loop is not executing? It reaches the for loop but just skips over the for loop at that point.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    Dim objContentPlaceHolder As ContentPlaceHolder
    Dim objLoginView As LoginView
    Dim objTreeView As TreeView

    objContentPlaceHolder = CType(Master.FindControl("ContentPlaceHolderBody"), ContentPlaceHolder)

    If Not objContentPlaceHolder Is Nothing Then

        objLoginView = CType(objContentPlaceHolder.FindControl("loginViewMain"), LoginView)

        If Not objLoginView Is Nothing Then
            objTreeView = CType(objLoginView.FindControl("TreeViewMain"), TreeView)

            ' Make sure all nodes for Maintenance are expanded.
            '--------------------------------------------------
            For Each treenode As TreeNode In objTreeView.Nodes
                If treenode.Text = "Maintenance" Then
                    treenode.Expand()
                End If
            Next treenode
        End If
    End If
End Sub

* Update *

I changed the page load event handler to a PreRenderComplete event handler and would you believe it worked? Not sure why PreRender didn't but that was it. Thanks again everyone for all the help.

Upvotes: 3

Views: 2438

Answers (2)

James Johnson
James Johnson

Reputation: 46047

From your example, it looks like your logic is only checking the root nodes. When dealing with hierarchical data, you need to employ recursive logic to ensure that the entire structure gets evaluated.

Something like this is what you need:

Protected Sub btnSearch_Click(sender As Object, e As EventArgs)
    For Each node As TreeNode In TreeView1.Nodes
        ExpandNodeByValue("Maintenance", node)
    Next
End Sub

Private Sub ExpandNodeByValue(value As String, parentNode As TreeNode)
    For Each childNode As TreeNode In parentNode.ChildNodes
        If childNode.Value.ToLower() = value.ToLower() Then
            childNode.Expand()
        End If
        If childNode.ChildNodes.Count > 0 Then
            ExpandNodeByValue(value, childNode)
        End If
    Next
End Sub

I would also suggest using a DirectCast instead of CType, at least temporarily, to ensure that the control is being found. You would implement that like this:

Dim objTreeView as TreeView = DirectCast(objLoginView.FindControl("TreeViewMain"), TreeView)
If objTreeView IsNot Nothing Then
    'The control was found
End If

Upvotes: 1

jbl
jbl

Reputation: 15413

   public Sub TreeView_TreeNodeDataBound(ByVal sender As Object, ByVal e As TreeNodeEventArgs  )
       dim mapNode as SiteMapNode =  e.Node.DataItem as SiteMapNode
       If mapNode.Title = "Maintenance" then
           e.Node.Expand()
       End if
   End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        Dim objContentPlaceHolder As ContentPlaceHolder
        Dim objLoginView As LoginView
        Dim objTreeView As TreeView

        objContentPlaceHolder = CType(Master.FindControl("ContentPlaceHolderBody"), ContentPlaceHolder)

        If Not objContentPlaceHolder Is Nothing Then

            objLoginView = CType(objContentPlaceHolder.FindControl("loginViewMain"), LoginView)

            If Not objLoginView Is Nothing Then
                objTreeView = CType(objLoginView.FindControl("TreeViewMain"), TreeView)
                objTreeView.TreeNodeDataBound += TreeView_TreeNodeDataBound 
            End If
        End If
    End Sub

Hope this will help

Upvotes: 1

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