ASP.NET TreeView - Keep only one parent node expanded

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A user recently asked me on the ASP.NET forums on how to expand only one parent node at a time. When the user clicks on a parent node, the ones that are already expanded (if any) should collapse. The answer to this question lies in the TreeNodeExpanded event as shown below:

TreeView markup

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

    ExpandDepth = "0" 

    ontreenodeexpanded="TreeView1_TreeNodeExpanded">

 <Nodes>

  <asp:TreeNode Text="Managers">

    <asp:TreeNode Text="Scott" Value="EID-XY34E" />

    <asp:TreeNode Text="Brinda" Value="EID-34D78" />

    <asp:TreeNode Text="Kathy" Value="EID-563D1" />

  </asp:TreeNode>

  <asp:TreeNode Text="Accounts">

    <asp:TreeNode Text="Laura" Value="EID-QQ21E" />

    <asp:TreeNode Text="Jemmica" Value="EID-YUR78" />

    <asp:TreeNode Text="Nicole" Value="EID-TG331" />

  </asp:TreeNode>

  <asp:TreeNode Text="Admin">

    <asp:TreeNode Text="Jack" Value="EID-PO41E" />

    <asp:TreeNode Text="Victor" Value="EID-HYR78" />

    <asp:TreeNode Text="Broady" Value="EID-KL931" />

  </asp:TreeNode>

</Nodes>

</asp:TreeView>

C#

protected void TreeView1_TreeNodeExpanded(object sender, 

    TreeNodeEventArgs e)

{

    string currValue = e.Node.Value.Trim();

    foreach (TreeNode tnode in TreeView1.Nodes)

    {

        if (tnode.Value != currValue)

        {

            tnode.Collapse();

        }

    }

}

VB.NET

    Protected Sub TreeView1_TreeNodeExpanded( _

    ByVal sender As Object, ByVal e As TreeNodeEventArgs)

        Dim currValue As String = e.Node.Value.Trim()

        For Each tnode As TreeNode In TreeView1.Nodes

            If tnode.Value <> currValue Then

                tnode.Collapse()

            End If

        Next tnode

    End Sub

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About The Author

Suprotim Agarwal, Developer Technologies MVP (Microsoft Most Valuable Professional) is the founder and contributor for DevCurry, DotNetCurry and SQLServerCurry. He is the Chief Editor of a Developer Magazine called DNC Magazine. He has also authored two Books - 51 Recipes using jQuery with ASP.NET Controls. and The Absolutely Awesome jQuery CookBook.

Follow him on twitter @suprotimagarwal.