ASP Update Panel - asp.net

Question

I implemented an update panel with a treeview control inside. The treeview control will cause a postback via Javascript which leads to the OnNodeChecked being triggered.
I have wrapped this in an UpdatePanel control, but I still get the blinking effect on my page. I also have a scriptManager implemented in the page. Does anyone know what I can do to avoid the flicker?
<asp:UpdatePanel ID="updateTreeViewPanel" runat="server"
ChildrenAsTriggers="true" UpdateMode="Conditional">
<ContentTemplate>
<fieldset>
<asp:TreeView ID="tv_WLG" runat="server"
OnTreeNodeCheckChanged="tv_WLG_TreeNodeCheckChanged"
OnSelectedNodeChanged="tv_WLG_SelectedNodeChanged"
onclick="javascript:postBackByObject(event)"
ShowCheckBoxes="All">
</asp:TreeView>
</fieldset>
</ContentTemplate>
</asp:UpdatePanel>

Answer 1

I would recomend adding a trigger...
<asp:UpdatePanel>
<ContentTemplate>
...your existing code
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="tv_WLG" />
</Triggers>
</asp:UpdatePanel>
The clientside script you're targeting may occur outside the scope of the update panel however. You might try handleing your click event in the codebehind instead.

Answer 2

What you can do is add an onload event to the updatepanel and trigger that using __doPostback() like so. Then whenever the click event fires you can handle it in the onload event of the updatepanel
<asp:UpdatePanel ID="updateTreeViewPanel" runat="server"
ChildrenAsTriggers="true" OnLoad="UpdatePanel_Load" UpdateMode="Conditional">
<ContentTemplate>
<fieldset>
<asp:TreeView ID="tv_WLG" runat="server"
OnTreeNodeCheckChanged="tv_WLG_TreeNodeCheckChanged"
OnSelectedNodeChanged="tv_WLG_SelectedNodeChanged"
onclick="__doPostback('updateTreeViewPanel', '');"
ShowCheckBoxes="All">
</asp:TreeView>
</fieldset>
</ContentTemplate>
</asp:UpdatePanel>
The reason your current method isn't working is because the postback object needs to be an object that is being handled by the update panel. Calling doPostback() with the update panel as the object will trigger the partial postback.