How can I clear the previous selection when an asp:TreeView is in an UpdatePanel?
-
03-07-2019 - |
Question
I have an ASP.Net 2.0 page that contains two UpdatePanels. The first panel contains a TreeView. The second panel contains a label and is triggered by a selection in the tree. When I select a node the label gets updated as expected and the TreeNode
that I clicked on becomes highlighted and the previously selected node is no longer highlighted. However if a node is original highlighted(selected) in the code-behind the highlight is not removed when selecting another node.
The markup
<asp:UpdatePanel ID="UpdatePanel1" runat="server" ChildrenAsTriggers="false" UpdateMode="Conditional">
<ContentTemplate>
<asp:TreeView ID="TreeView1" runat="server" OnSelectedNodeChanged="TreeView1_SelectedNodeChanged">
<SelectedNodeStyle BackColor="Pink" />
</asp:TreeView>
</ContentTemplate>
</asp:UpdatePanel>
<asp:UpdatePanel ID="UpdatePanel2" runat="server" ChildrenAsTriggers="True">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text=" - "></asp:Label>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="TreeView1" EventName="SelectedNodeChanged" />
</Triggers>
</asp:UpdatePanel>
The code behind
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
TreeView1.Nodes.Add(new TreeNode("Test 1", "Test One"));
TreeView1.Nodes.Add(new TreeNode("Test 2", "Test Two"));
TreeView1.Nodes.Add(new TreeNode("Test 3", "Test Three"));
TreeView1.Nodes.Add(new TreeNode("Test 4", "Test Four"));
TreeView1.Nodes[0].Selected = true;
}
}
protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
{
Label1.Text = TreeView1.SelectedValue;
}
The at the start the first node is selected. Why is its highlight not removed when selecting another node?
Also, I asked a different question about the same setup that I haven't got an answer for. Any help would appreciated.
Edit I know that setting ChildrenAsTriggers="false"
will work but I want to avoid rendering the tree again as it can be very large.
Solution 3
This may be a bit of a hack but this will clear the selection on the client and avoid updating the panel.
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(function BeginRequestHandler(sender, args)
{
var elem = args.get_postBackElement();
var selectedClassName = elem.id + '_1';
var arrAllElements = GetElementsByClassName(selectedClassName, elem);
var selectedNode = $get(elem.id + '_SelectedNode').value;
for(var i = 0; i < arrAllElements.length; i++)
{
if(arrAllElements[i].childNodes[0].id != selectedNode)
RemoveClassName(arrAllElements[i], selectedClassName );
}
}
);
It removes the selected style/class from all tree nodes unless its value is contained in the '_SelectedNode' hidden field.
GetElementsByClassName
and RemoveClassName
are in my own js library but are obvious enough.
OTHER TIPS
/// <summary>
/// Remove selection from TreeView
/// </summary>
/// <param name="tree"></param>
public static void ClearTreeView(TreeView tree)
{
if (tree.SelectedNode != null)
{
tree.SelectedNode.Selected = false;
}
}
You need to set the selection to false for all nodes.
I use something like this for one of my applications (with my treeview tvCategories):
public void RefreshSelection(string guid)
{
if (guid == string.Empty)
ClearNodes(tvCategories.Nodes);
else
SelectNode(guid, tvCategories.Nodes);
}
private void ClearNodes(TreeNodeCollection tnc)
{
foreach (TreeNode n in tnc)
{
n.Selected = false;
ClearNodes(n.ChildNodes);
}
}
private bool SelectNode(string guid, TreeNodeCollection tnc)
{
foreach (TreeNode n in tnc)
{
if (n.Value == guid)
{
n.Selected = true;
return true;
}
else
{
SelectNode(guid, n.ChildNodes);
}
}
return false;
}