Collapse all Open Nodes Of an ASP.NET TreeView when Another Node is expanded

Users have a very common requirement around the ASP.NET TreeView - that is to keep only one TreeNode expanded at a given point of time. So if a TreeNode in the TreeView is expanded, collapse the other open TreeNodes. Here's how to do so:

 <asp:TreeView ID="TreeView1" runat="server"

        ontreenodeexpanded="TreeView1_TreeNodeExpanded">

        <Nodes>

            <asp:TreeNode Text="Node1" Value="Node1">

                <asp:TreeNode Text="Node1.1" Value="Node1.1"/>

                <asp:TreeNode Text="Node1.2" Value="Node1.2"/>

                <asp:TreeNode Text="Node1.3" Value="Node1.3"/>

            </asp:TreeNode>

            <asp:TreeNode Text="Node2" Value="Node2">

                <asp:TreeNode Text="Node1.1" Value="Node2.1"/>

                <asp:TreeNode Text="Node1.2" Value="Node2.2"/>

            </asp:TreeNode>

            <asp:TreeNode Text="Node3" Value="Node3">

                <asp:TreeNode Text="Node3.1" Value="Node3.1"/>

                <asp:TreeNode Text="Node3.2" Value="Node3.2"/>

            </asp:TreeNode>

        </Nodes>

</asp:TreeView>

C#

protected void TreeView1_TreeNodeExpanded(object sender, TreeNodeEventArgs e)

{

    // Loop through all nodes

    foreach (TreeNode treenode in TreeView1.Nodes)

    {

        // If node is expanded

        if (treenode != e.Node)

        {

            // Collapse all other nodes

            treenode.Collapse();    

        }

    }

}

VB.NET

    Protected Sub TreeView1_TreeNodeExpanded(ByVal sender As Object, ByVal e As TreeNodeEventArgs)

        ' Loop through all nodes

        For Each treenode As TreeNode In TreeView1.Nodes

            ' If node is expanded

            If treenode IsNot e.Node Then

                ' Collapse all other nodes

                treenode.Collapse()

            End If

        Next treenode

    End Sub

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About The Author

Suprotim Agarwal, ASP.NET Architecture MVP works as an Architect Consultant and provides consultancy on how to design and develop Web applications.

Suprotim is also the founder and primary contributor to DevCurry, DotNetCurry and SQLServerCurry. He has also written an EBook 51 Recipes using jQuery with ASP.NET Controls.

Follow him on twitter @suprotimagarwal