You can show any level of nested subgrids (master detail) inside a parent grid. Just set the HierarchySettings.HierarchyMode property of the parent grid to "Parent" for the parent grid and to "Child" for the child ones. If you have a grid that is a parent and a child at the same time (e.g. the second level grid in a 3 level hierarchy), set its HierarchySettings.HierarchyMode property to "ParentAndChild".

Then, hook the client-side ClientSideEvents.OnClientSubGridRowExpanded event of the grid and call a special javascript function, which is autogenerated by child grids and is called showSubGrid_{GridID}, where {GridID} is the ID of the child grid, e.g. showSubGrid_JQGrid2

It's as simple as that, this will in essense trigger the sever-side OnDataRequesting of the grid and you can get the ID of the parent row and bind the child grid accordingly.

Complete hierarchy is achieved in this example with just 2 lines of code - 1 javascript and 1 C# (check the ASPX and C# tabs for details).
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Trirand.Web.Mvc;
using System.Web.UI.WebControls;

namespace JQGridMVCExamples.Models
{
    public class ThreeLevelHierarchyJqGridModel
    {
        public JQGrid CustomersGrid { get; set; }
        public JQGrid OrdersGrid { get; set; }
        public JQGrid OrderDetailsGrid { get; set; }

        public ThreeLevelHierarchyJqGridModel()
        {
            CustomersGrid = new JQGrid
            {
                Columns = new List()
                                 {
                                     new JQGridColumn { DataField = "CustomerID",
                                                        HeaderText = "ID",
                                                        PrimaryKey = true,
                                                        Width = 50 },
                                     new JQGridColumn { DataField = "CompanyName" },
                                     new JQGridColumn { DataField = "ContactName" },
                                     new JQGridColumn { DataField = "Phone" },
                                     new JQGridColumn { DataField = "City" }
                                 },
                 Width = Unit.Pixel(650),
                 Height = Unit.Pixel(350)
            };

            OrdersGrid = new JQGrid
            {
                Columns = new List()
                                 {
                                     new JQGridColumn { DataField = "OrderID", 
                                                        // always set PrimaryKey for Add,Edit,Delete operations
                                                        // if not set, the first column will be assumed as primary key
                                                        PrimaryKey = true,
                                                        Editable = false,
                                                        Width = 50 },
                                     new JQGridColumn { DataField = "OrderDate", 
                                                        Editable = true,
                                                        Width = 100, 
                                                        DataFormatString = "{0:d}" },
                                     new JQGridColumn { DataField = "CustomerID", 
                                                        Editable = true,
                                                        Width = 50 },
                                     new JQGridColumn { DataField = "Freight", 
                                                        Editable = true,
                                                        Width = 75 },
                                     new JQGridColumn { DataField = "ShipName",
                                                        Editable =  true,
                                                        Width = 100
                                                      }                                     
                                 },
                Width = Unit.Pixel(450),
                Height = Unit.Percentage(100)                
            };
            OrdersGrid.ToolBarSettings.ShowRefreshButton = true;

            OrderDetailsGrid = new JQGrid
            {
                Columns = new List()
                                 {
                                     new JQGridColumn { DataField = "OrderID",                                                        
                                                        PrimaryKey = true,
                                                        Width = 50 },
                                     new JQGridColumn { DataField = "ProductID" },
                                     new JQGridColumn { DataField = "UnitPrice", Width = 200 }                                     
                                 },
                Width = Unit.Pixel(350),
                Height = Unit.Percentage(100)
            };
  
        }
    }
}
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<JQGridMVCExamples.Models.ThreeLevelHierarchyJqGridModel>" %>
<%@ Import Namespace="Trirand.Web.Mvc" %>
<%@ Import Namespace="JQGridMVCExamples.Models" %>

<!DOCTYPE html>
<html lang="en-us">
<head id="Head1" runat="server">
    <meta charset="utf-8">
    <title>jqGrid for ASP.NET MVC - Hierarchy Three Levels</title>    
    <!-- The jQuery UI theme that will be used by the grid -->
    <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 jqGrid needs -->    
    <link rel="stylesheet" type="text/css" href="http://www.trirand.net/aspnetmvc/Content/themes/ui.jqgrid.css" />
    <!-- jQuery runtime minified -->
    <script src="http://ajax.microsoft.com/ajax/jquery/jquery-2.0.3.min.js" type="text/javascript"></script>
    <!-- The localization file we need, English in this case -->
    <script type="text/javascript" src="http://www.trirand.net/aspnetmvc/Scripts/trirand/i18n/grid.locale-en.js"></script>
    <!-- The jqGrid client-side javascript -->
    <script type="text/javascript" src="http://www.trirand.net/aspnetmvc/Scripts/trirand/jquery.jqGrid.min.js"></script>
</head>
<body>    
    <div>                   
        <%= Html.Trirand().JQGrid(Model.CustomersGrid, "CustomersGrid") %>
        <%= Html.Trirand().JQGrid(Model.OrdersGrid, "OrdersGrid") %>
        <%= Html.Trirand().JQGrid(Model.OrderDetailsGrid, "OrderDetailsGrid") %>
        
        <script type="text/javascript">
            function showOrdersSubGrid(subgrid_id, row_id) {            
                // the "showSubGrid_OrdersGrid" function is autogenerated and available globally on the page by the second child grid. 
                // Calling it will place the child grid below the parent expanded row and will call the action specified by the DaraUrl property
                // of the child grid, with ID equal to the ID of the parent expanded row                
                showSubGrid_OrdersGrid(subgrid_id, row_id);
            }

            function showOrderDetailsSubGrid(subgrid_id, row_id) {
                // the "showSubGrid_OrderDetailsGrid" function is autogenerated and available globally on the page by the second child grid. 
                // Calling it will place the child grid below the parent expanded row and will call the action specified by the DaraUrl property
                // of the child grid, with ID equal to the ID of the parent expanded row                
                showSubGrid_OrderDetailsGrid(subgrid_id, row_id);
            }
            
            function showDialog()
            {
                alert("Show Add Dialog");
            }
    </script>

    </div>
    <br /><br />
    <div>
        <% Html.RenderPartial("CodeTabs"); %>        
    </div>
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using JQGridMVCExamples.Models;
using Trirand.Web.Mvc;

namespace JQGridMVCExamples.Controllers.Grid
{
    public partial class GridController : Controller
    {
        // This is the default action for the View. Use it to setup your grid Model.
        public ActionResult HierarchyThreeLevels()
        {
            // Get the model (setup) of the grid defined in the /Models folder.
            var model = new ThreeLevelHierarchyJqGridModel();
            SetUpThreeLevelGrids(model);

            // Pass the custmomized grid model to the View
            return View(model);
        }

        public JsonResult ThreeLevel_CustomersDataRequested()
        {
            // Get both the grid Model and the data Model
            // The data model in our case is an autogenerated linq2sql database based on Northwind.
            var northWindModel = new NorthwindDataContext();
            var model = new ThreeLevelHierarchyJqGridModel();
            SetUpThreeLevelGrids(model);

            // return the result of the DataBind method, passing the datasource as a parameter
            // jqGrid for ASP.NET MVC automatically takes care of paging, sorting, filtering/searching, etc
            return model.CustomersGrid.DataBind(northWindModel.Customers);
        }

        // parentRowID is automatically passed from the parent grid to the child grid. Note: parentRowID is case sensitive
        public JsonResult ThreeLevel_OrdersDataRequested(string parentRowID)
        {
            // Get both the grid Model and the data Model
            // The data model in our case is an autogenerated linq2sql database based on Northwind.
            var northWindModel = new NorthwindDataContext();
            var model = new ThreeLevelHierarchyJqGridModel();
            SetUpThreeLevelGrids(model);

            var orders = from o in northWindModel.Orders
                         where o.CustomerID == parentRowID
                         select o;
            
            return model.OrdersGrid.DataBind(orders);
        }

        // parentRowID is automatically passed from the parent grid to the child grid. Note: parentRowID is case sensitive
        public JsonResult ThreeLevel_OrderDetailsDataRequested(string parentRowID)
        {
            // Get both the grid Model and the data Model
            // The data model in our case is an autogenerated linq2sql database based on Northwind.
            var northWindModel = new NorthwindDataContext();
            var model = new ThreeLevelHierarchyJqGridModel();
            SetUpThreeLevelGrids(model);

            var orderDetails = from o in northWindModel.Order_Details
                         where o.OrderID == Convert.ToInt32(parentRowID)
                         select o;

            return model.OrderDetailsGrid.DataBind(orderDetails);
        }



        public void SetUpThreeLevelGrids(ThreeLevelHierarchyJqGridModel model)
        {
            var customersGrid = model.CustomersGrid;
            var ordersGrid = model.OrdersGrid;
            var orderDetailsGrid = model.OrderDetailsGrid;

            customersGrid.ID = "CustomersGrid";
            customersGrid.DataUrl = Url.Action("ThreeLevel_CustomersDataRequested");
            customersGrid.HierarchySettings.HierarchyMode = HierarchyMode.Parent;
            customersGrid.ClientSideEvents.SubGridRowExpanded = "showOrdersSubGrid";
            customersGrid.ToolBarSettings.ShowEditButton = true;
            customersGrid.ToolBarSettings.ShowAddButton = true;
            customersGrid.AddDialogSettings.Caption = "Master Grid Add";
            customersGrid.EditDialogSettings.Caption = "Master Grid Edit";
            customersGrid.ClientSideEvents.AfterAddDialogShown = "showDialog";

            ordersGrid.ID = "OrdersGrid";
            ordersGrid.DataUrl = Url.Action("ThreeLevel_OrdersDataRequested");
            ordersGrid.HierarchySettings.HierarchyMode = HierarchyMode.ParentAndChild;
            ordersGrid.ClientSideEvents.SubGridRowExpanded = "showOrderDetailsSubGrid";
            ordersGrid.ToolBarSettings.ShowEditButton = true;
            ordersGrid.ToolBarSettings.ShowAddButton = true;
            ordersGrid.AddDialogSettings.Caption = "Child Grid Add";
            ordersGrid.EditDialogSettings.Caption = "Child Grid Edit";
            ordersGrid.ClientSideEvents.AfterAddDialogShown = "showDialog";

            orderDetailsGrid.ID = "OrderDetailsGrid";
            orderDetailsGrid.DataUrl = Url.Action("ThreeLevel_OrderDetailsDataRequested");
            orderDetailsGrid.HierarchySettings.HierarchyMode = HierarchyMode.Child;
            orderDetailsGrid.ToolBarSettings.ShowEditButton = true;
        }
    }
}
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" />