Maintaining TreeView state across postbacks

[stricknyn]

Hello, all,

Is it possible to maintain treeview state across postbacks? I want my users to have a positive experience. I have a treeview on a masterpage. I want the treeview to maintain its expand/colapse state when the user navigates to different pages. An this be done? I'm using ASP.NET 2.0 with VB 2005.

Thanks!

Strick

[mendhak]

If you're using ASP.NET 2.0, read this:
http://blog.binaryocean.com/PermaLin...c8da35636.aspx

[Wokawidget]

I had a similar issue, but my treeview was on my master page and so when I visited another page the treeview got wiped...as you would expect.

The above code just records which nodes were expanded, and not the nodes themselves.

I played with the code and then simply tried to store the treeview's nodes collection in session. This seemed to work a treat. the code I came up with was:

Public Class TreeViewState

    Public Shared Function IsTreeViewStateSaved(ByVal treeView As TreeView, ByVal key As String) As Boolean
        Dim isSaved As Boolean = (HttpContext.Current.Session(key + treeView.ID) IsNot Nothing)

        Return isSaved
    End Function

    Public Shared Sub SaveTreeView(ByVal treeView As TreeView, ByVal key As String)
        HttpContext.Current.Session(key + treeView.ID) = treeView.Nodes
    End Sub

    Public Shared Sub RestoreTreeView(ByVal treeView As TreeView, ByVal key As String)
        If IsTreeViewStateSaved(treeView, key) Then
            treeView.Nodes.Clear()

            Dim nodes As TreeNodeCollection = CType(HttpContext.Current.Session(key + treeView.ID), TreeNodeCollection)
            For index As Integer = nodes.Count - 1 To 0 Step -1
                treeView.Nodes.AddAt(0, nodes.Item(index))
            Next index

            HttpContext.Current.Session(key + treeView.ID) = Nothing
        End If
    End Sub

End Class

In the unload event of the treeview on the materpage use:

TreeViewState.SaveTreeview(tvwUsers, "Woka")

and in the master page load use:

If TreeViewState.IsTreeViewStateSaved(tvwUsers, "Woka") Then
   TreeViewState.RestoreTreeViewState(tvwUsers, "Woka")
End If

Hope that helps.

Have I missed something with this code? I have made loads of daft errors today and no doubt, knowing my luck, one will be in the above.

Anyways, from what I can see it works a treat. The nodes, their properties and their expanded state gets restored.

Woof

[Dorwin]

Thanks for the code. It does exactly what I was looking for. Works great!