The property I was referring to isn't exposed in our default navigation. You can set it declaratively to a custom RadTreeView navigation, created in Visual Studio (an .ascx file with a SiteMapDataSource). Then this navigation can be registered in Sitefinity as a new control.
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="RedTreeView.ascx.cs" Inherits="SitefinityWebApp.Controls.RedTreeView" %>
<%@ Register TagPrefix="sf" Namespace="Telerik.Web.UI" Assembly="Telerik.Web.UI" %>
The above markup can also be used as a tempate for the default TreeView navigation in Sitefinity. For this purpose you should enter the relative path to the .ascx file in the Design settings
of the navigation, as shown in the attached image.
Another option would be to simply change the default Skin, which is set to the navigation - Sitefinity skin, by entering the name of your custom skin in the Wrapper CSS class
This automatically removes the line images, which are set to the TreeView (screenshot TreeViewLines).
Let me know if you need additional assistance.
the Telerik team
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