Adding items to a dropdownlist instance is easy - just create a new JQListItem instance for each item, set its Text property and add it to the Items collection of the dropdownlist instance.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="default.aspx.cs" Inherits="JQSuiteASPNETExample.examples.multiselect.loaddatabase._default" %>
<%@ Register Assembly="Trirand.Web" TagPrefix="trirand" Namespace="Trirand.Web.UI.WebControls" %>

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
    <title>jqMultiSelect for ASP.NET WebForms - Load from DataBase</title>
    <!-- The jQuery UI theme that will be used by the multiselect  -->
    <link rel="stylesheet" type="text/css" href="http://ajax.aspnetcdn.com/ajax/jquery.ui/1.10.3/themes/redmond/jquery-ui.css" />    
    <!-- The jQuery UI theme extension the multiselect needs -->
    <link rel="stylesheet" type="text/css" href="/themes/ui.jqmultiselect.css" />
    <!-- jQuery runtime minified -->
    <script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery/jquery-2.0.3.min.js"></script>
    <!-- The jqMultiSelect client-side javascript -->
    <script type="text/javascript" src="/js/trirand/jquery.jqmultiselect.min.js"></script>
    <style type="text/css">    
        body, html { font-size: 80%; }
    </style>
</head>
<body>    
    <form id="Form1" runat="server">
    <table cellpadding="10" cellspacing="10">
        <tr>
            <td valign="top">
                <trirand:JQMultiSelect 
                    ID="JQMultiSelect1"
                    Filter="StartsWith"
                    Height="200"
                    Width="450"                    
                    runat="server">
                </trirand:JQMultiSelect>
            </td>           
        </tr>
    </table>   
    
    <br /><br /><br />
    <br /><br /><br />
    
    <div>
        <trirand:codetabs runat="server" ID="tabs"></trirand:codetabs>
    </div>
    
    </form>
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using JQSuiteASPNETExample.dbml;
using Trirand.Web.UI.WebControls;

namespace JQSuiteASPNETExample.examples.multiselect.loaddatabase
{
    public partial class _default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                var northWindModel = new DataClasses1DataContext();
                List orders = northWindModel.Orders.ToList();

                foreach (Order order in orders)
                {
                    // only add items if they are not already added to the combobox
                    if (JQMultiSelect1.FindItemByText(order.ShipName) == null)
                    {
                        JQMultiSelect1.Items.Add(
                            new JQListItem
                            {
                                Text = order.ShipName,
                                Value = order.CustomerID
                            });
                    }
                }
            }

        }
    }
}
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" />