Question

I have a tree view that I’m dynamically loading on the PageLoad event. Here is my tree view and data source:

<asp:TreeView ID="tv" runat="server" DataSourceID="xds"
    SelectedNodeStyle-ForeColor="Red" NodeStyle-ForeColor="Black">   
    <DataBindings>
        <asp:TreeNodeBinding DataMember="Node"
            ValueField="Id" TextField="Title"  />
    </DataBindings>
</asp:TreeView>
<asp:XmlDataSource ID="xds" runat="server" EnableCaching="false" />

This is the code I run on PageLoad

StringBuilder sb = new StringBuilder();
XmlWriter xw = XmlWriter.Create(sb);

WriteTreeViewXml(xw);
xw.Flush();
xw.Close();

xds.Data = sb.ToString();
xds.DataBind();

tv.Nodes[0].Selected = true;  // error here

This works fine, the tree view gets loaded correctly. Now I’m trying to add styling to the SelectedNode. This works when I click on a specific node, but the root node isn’t styled when the page loads. So I’m trying to set the root node to selected on PageLoad

I get this error when I try to set the root node as selected:

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

For some reason the tree view is empty after I bind the data source.

Does anyone know how I can do this?

Answer 1

You need to call tv.Databind() after the line that calls xds.DataBind(); Otherwise the control isn’t being bound to the datasource. I believe it would do this for you if you were declaratively setting the XmlDataSource (to a static file, for example), but since you are manually populating it, you’ll need to manually call the control’s DataBind method as well.