The Selected property of each JQListItem instance can be set to mark the item as selected. Upon posting back to the server, the {DropDownListID}_selectedValue field holds the Value of the selected item. Please, review the the code in the Controller for details on how this can be achieved.
@using Trirand.Web.Mvc

<!DOCTYPE html>
<html lang="en-us">
<head>
    <meta charset="utf-8">
    <title>jqDropDownList for ASP.NET MVC - Selection</title>    
    <!-- The jQuery UI theme that will be used by jqDropDownList -->
    <script src="~/Scripts/jquery-3.0.0.min.js" type="text/javascript"></script>
    <!-- The jqTreeView client-side javascript -->
    <script src="~/Scripts/trirand/jquery.jqDropDownList.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/1.11.4/themes/redmond/jquery-ui.css" />
    <!-- The jQuery UI theme extension jqTreeView needs -->
    <link rel="stylesheet" type="text/css" href="~/Content/themes/ui.jqDropDownList.css" />
</head>
<body>    
    @{ Html.BeginForm("Selection", "DropDownList"); }

    @(Html.Trirand().JQDropDownList(
                new JQDropDownList
                {
                    Width = 150,
                    Items = ViewData["items"] as List<JQListItem>
                }, "combobox"))
            
    <br />
    <br />
    
    @if (ViewData["message"] != null && ViewData["message"].ToString().Length > 0) { 
        <span style="font-size:120%; font-family: Tahoma">@ViewData["message"]</span>
      } 
    
   
     <br /><br />
     
    <input type="button" 
            id="showSelectedItemButton" 
            value="Show Selected Item" onclick="this.form.submit();" /> 
            
     @{ Html.EndForm(); }
     
    <br /><br /><br />
    <br /><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.DropDownList
{
    public partial class DropDownListController : Controller
    {
        public ActionResult Selection(string DropDownList_selectedValue)
        {
            // load items and set selected one based on previsous selection
            // ViewData["items"] will be used in the View to populate the dropdown
            ViewData["items"] = GetItems(DropDownList_selectedValue);

            if (!String.IsNullOrEmpty(DropDownList_selectedValue))
            {
                ViewData["message"] = "<b>Selected Item</b>: " + DropDownList_selectedValue;
            }
            return View();
        }

        public List<JQListItem> GetItems(string selectedValue)
        {
            List<JQListItem> items = new List<JQListItem>
                    {
                        new JQListItem { 
                            Text = "One", 
                            Value = "One",
                            ImageUrl = "/content/images/folder.png"
                        },
                        new JQListItem 
                        { 
                            Text = "Two", 
                            Value = "Two",
                            ImageUrl = "/content/images/folder-open.png"
                        },
                        new JQListItem 
                        { 
                            Text = "Three", 
                            Value = "Three",
                            ImageUrl = "/content/images/document.png"
                        }
                    };

            if (!String.IsNullOrEmpty(selectedValue))
            {
                var item = items.Find(i => i.Value == selectedValue);
                if (item != null)
                    item.Selected = true;
            }

            return items;
        }
    }
}
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" />