The Enabled property of each JQTreeNode instance can be set to mark the node as enabled/disabled. Nodes that are disabled cannot be hovered, expanded, checked or selected.
@using Trirand.Web.Mvc
@using MVCDemo.Models
@using System.Web.UI.WebControls

<!DOCTYPE html>
<html lang="en-us">
<head>
    <meta charset="utf-8">
    <title>jqTreeView for ASP.NET MVC - Disabled Nodes</title>    
    <!-- jQuery runtime minified -->
    <script src="~/Scripts/jquery-3.2.1.min.js" type="text/javascript"></script>
    <!-- The jqTreeView client-side javascript -->
    <script src="~/Scripts/trirand/jquery.jqTreeView.min.js" type="text/javascript"></script>
    <!-- The jQuery UI theme that will be used by the grid. -->
    <link rel="stylesheet" type="text/css" href="http://code.jquery.com/ui/1.12.1/themes/redmond/jquery-ui.css" />
    <!-- The jQuery UI theme extension jqTreeView needs -->
    <link rel="stylesheet" type="text/css" href="~/Content/themes/ui.jqtreeview.css" />
</head>
<body>    

    <div>
    @(Html.Trirand().JQTreeView(
                new JQTreeView
                {
                    DataUrl = Url.Action("TreeView_DisabledNode_DataRequested"),
                    Height = Unit.Pixel(300),
                    Width = Unit.Pixel(300)                               
                }, "DisabledNodeTreeView"))           
    </div>
            
    <br />
    <br />
    <div>
          
    </div>
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Trirand.Web.Mvc;

namespace MVCDemo.Controllers.Tree
{
    public partial class TreeController : Controller
    {
        public ActionResult DisabledNode()
        {
            return View();
        }

        public JsonResult TreeView_DisabledNode_DataRequested()
        {
            var tree = new JQTreeView();

            List<JQTreeNode> nodes = new List<JQTreeNode>();

            nodes.Add(new DisabledLeafNode { Text = "One", Enabled = false });
            nodes.Add(new DisabledFolderNode { Text = "Two", Expanded = true });
            nodes.Add(new DisabledLeafNode { Text = "Three" });

            var secondNode = nodes.Find(n => n.Text == "Two");

            secondNode.Nodes.Add(new DisabledLeafNode { Text = "2.1" });
            secondNode.Nodes.Add(new DisabledFolderNode { Text = "2.2", Expanded = false, Enabled = false });
            secondNode.Nodes.Add(new DisabledLeafNode { Text = "2.3" });

            secondNode.Nodes.Find(n => n.Text == "2.2").Nodes.Add(new DisabledLeafNode { Text = "2.2.1" });
            secondNode.Nodes.Find(n => n.Text == "2.2").Nodes.Add(new DisabledLeafNode { Text = "2.2.2" });
            secondNode.Nodes.Find(n => n.Text == "2.2").Nodes.Add(new DisabledLeafNode { Text = "2.2.4" });
            secondNode.Nodes.Find(n => n.Text == "2.2").Nodes.Add(new DisabledLeafNode { Text = "2.2.3" });            

            return tree.DataBind(nodes);
        }

        public class DisabledFolderNode : JQTreeNode
        {
            public DisabledFolderNode()
            {
                ImageUrl = "/content/images/folder.png";
                ExpandedImageUrl = "/content/images/folder-open.png";
            }                
        }

        public class DisabledLeafNode : JQTreeNode
        {
            public DisabledLeafNode()
            {
                ImageUrl = "/content/images/document.png";        
            }
        }
    }
}
Switch theme:


Theming is based on the very popular jQuery ThemeRoller standard. This is the same theming mechanism used by jQuery UI and is now a de-facto standard for jQuery based components. The benefits of using ThemeRoller are huge. We can offer a big set of ready to use themes created by professional designers, including Windows-like themes (Redmond), Apple-like theme (Cupertino), etc. In addition to that any jQuery UI controls on the same page will pick the same theme.

Last, but not least, you can always roll your own ThemeRoller theme, using the superb Theme Editor

To use a theme, simply reference 2 Css files in your Html <head> section - the ThemeRoller theme you wish to use, and the jqGrid own ThemeRoller Css file. For example (Redmond theme):

<link rel="stylesheet" type="text/css" media="screen" href="/themes/redmond/jquery-ui-1.8.2.custom.css" />
<link rel="stylesheet" type="text/css" media="screen" href="/themes/ui.jqgrid.css" />