You can initiate new row adding from the toolbar ("+" button) or from an external control. In this example, we are using the toolbar ToolBarSettings.ShowAddButton=True

Just handle the RowAdding event on the server. It is callled via ajax request from jqGrid and in the event arguments you will have the values of the new cells to add (eventArgs.RowData). Then just add new row in your datasource, fill it with the respective values and rebind the grid.

In this example we have used ADO.NET as a sample datasource, but this approach will work for any type of datasource you have.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI.WebControls;
using Trirand.Web.Mvc;

namespace MVCDemo.Models
{
    public class OrdersJqGridModel
    {
        public JQGrid OrdersGrid { get; set; }

        public OrdersJqGridModel()
        {
            OrdersGrid = new JQGrid
            {
                Columns = new List<JQGridColumn>()
                {
                    new JQGridColumn 
                    {
                        // Always set PrimaryKey for Add,Edit,Delete operations
                        // If not set, the first column will be assumed as primary key
                        DataField = "OrderID",                                        
                        PrimaryKey = true,
                        Editable = false,
                        Width = 50,
                        DataType = typeof(int)
                    },                                    
                    new JQGridColumn 
                    { 
                        DataField = "CustomerID", 
                        Editable = true,
                        Width = 100,
                        DataType = typeof(string)
                    },
                    new JQGridColumn 
                    { 
                        DataField = "OrderDate",                                                         
                        Editable = true,
                        Width = 100, 
                        DataFormatString = "{0:yyyy/MM/dd}",
                        DataType = typeof(DateTime)
                    },
                    new JQGridColumn
                    { 
                        DataField = "Freight", 
                        Editable = true,
                        Width = 75,
                        DataType = typeof(double)
                    },
                    new JQGridColumn 
                    { 
                        DataField = "ShipName",
                        Editable =  true,
                        Width = 150,
                        DataType = typeof(string)
                    }
                },
                
                Width = Unit.Pixel(640),
                Height = Unit.Percentage(100),
                
                ToolBarSettings = new ToolBarSettings
                {
                    ShowRefreshButton = true
                }
            };  
        }        
    }
}
@model MVCDemo.Models.OrdersJqGridModel
@using Trirand.Web.Mvc
@using MVCDemo.Models

<!DOCTYPE html>
<html lang="en-us">
<head>
    <meta charset="utf-8">
    <title>jqGrid for ASP.NET MVC - Add Rows Dialogs</title>    
    <!-- jQuery runtime minified -->
    <script src="~/Scripts/jquery-3.0.0.min.js" type="text/javascript"></script>
    <!-- The jqGrid localization file we need, English in this case -->
    <script type="text/javascript" src="../../Scripts/trirand/i18n/grid.locale-en.js"></script>
    <!-- The jqGrid client-side javascript -->
    <script type="text/javascript" src="../../Scripts/trirand/jquery.jqGrid.min.js"></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 jqGrid needs -->    
    <link rel="stylesheet" type="text/css" href="../../Content/themes/ui.jqgrid.css" />  
</head>
<body>
    <div>
        @Html.Trirand().JQGrid(Model.OrdersGrid, "AddDialogGrid")
    </div>
    <br /><br />
    <div>
          
    </div>
</body>
</html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using MVCDemo.Models;
using Trirand.Web.Mvc;

namespace MVCDemo.Controllers.Grid
{
    public partial class GridController : Controller
    {
        // This is the default action for the View. Use it to setup your jqGrid Model.
        public ActionResult EditAddDialog()
        {
            // Get the model (setup) of the grid defined in the /Models folder.
            var gridModel = new OrdersJqGridModel();
            gridModel.OrdersGrid.AddDialogSettings.CloseAfterAdding = true;
            // This method sets common properties for the grid, different than the default in the Model
            EditAddDialog_SetUpGrid(gridModel.OrdersGrid);

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

        // This method is called when the grid requests data. You can choose any method to call
        // by setting the JQGrid.DataUrl property. We are doing this in the EditAddDialog_SetUpGrid method.
        public JsonResult EditAddDialog_DataRequested()
        {
            // Get both the grid and data models. For data model, make sure IQueryable is implemented (most linq-2-* cases)
            // The data model in our case is an autogenerated linq2sql database based on Northwind.
            var gridModel = new OrdersJqGridModel();
            var dataModel = GetOrders().AsQueryable();

            // This method sets common properties for the grid, different than the default in the Model
            EditAddDialog_SetUpGrid(gridModel.OrdersGrid);

            // 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 gridModel.OrdersGrid.DataBind(dataModel);
        }

        // The data gets passed to the controller as strongly typed objects of your data model, Order in our case
        // This functionality is called Model Binders in ASP.NET MVC terms
        public void EditAddDialog_EditRow(Order newOrder)
        {
            // Get the grid and database (northwind) models
            var gridModel = new OrdersJqGridModel();
            var dataModel = GetOrders().AsQueryable();

            // If we are in "AddRow" mode, get the Order from database that matches the edited order
            // Check for "AddRow" mode this way, we can also be in "Edit" or "Delete" mode as well in this method
            if (gridModel.OrdersGrid.AjaxCallBackMode == AjaxCallBackMode.AddRow)
            {
                List<Order> gridData = GetOrders();
                // In this demo we do not need to update the database since we are using Session
                // In your case you may need to actually hit the database. Also, make sure you set a unique primary key
                newOrder.OrderID = gridData.Max<Order>(o => o.OrderID) + 1;
                gridData.Insert(0, newOrder);

                // This will save the changes into the database. We have commented this since this is just an online demo
                // var northWindModel = new NorthwindDataContext();
                // northWindModel.Orders.InsertOnSubmit(newOrder);
                // northWindModel.SubmitChanges();
            }
        }

        public void EditAddDialog_SetUpGrid(JQGrid ordersGrid)
        {
            ordersGrid.DataUrl = Url.Action("EditAddDialog_DataRequested");
            ordersGrid.EditUrl = Url.Action("EditAddDialog_EditRow");
            ordersGrid.ToolBarSettings.ShowAddButton = true;
            ordersGrid.AddDialogSettings.CloseAfterAdding = true;

            // setup the dropdown values for the CustomerID editing dropdown
            EditAddDialog_SetUpCustomerIDColumn(ordersGrid);
        }

        private void EditAddDialog_SetUpCustomerIDColumn(JQGrid ordersGrid)
        {
            // setup the grid search criteria for the columns
            JQGridColumn customersColumn = ordersGrid.Columns.Find(c => c.DataField == "CustomerID");
            customersColumn.Editable = true;
            customersColumn.EditType = EditType.DropDown;

            // Populate the search dropdown only on initial request, in order to optimize performance
            if (ordersGrid.AjaxCallBackMode == AjaxCallBackMode.RequestData)
            {
                var northWindModel = new NorthwindDataContext();
                var editList = from customers in northWindModel.Customers
                               select new SelectListItem
                               {
                                   Text = customers.CustomerID,
                                   Value = customers.CustomerID
                               };

                customersColumn.EditList = editList.ToList<SelectListItem>();
            }
        }


        // This is a helper method fetching the data from Session
        public List<Order> EditAddDialog_GetOrders()
        {
            List<Order> orders;
            if (Session["Orders"] == null)
            {
                var northWindModel = new NorthwindDataContext();
                orders = (from order in northWindModel.Orders
                          select order).ToList<Order>();
                Session["Orders"] = orders;
            }
            else
            {
                orders = Session["Orders"] as List<Order>;
            }

            return orders;
        }
    }
}
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" />