You can handle validation on the server-side as well and perform any custom logic. If, for some reason, the data submitted does not validate, you can use the JQGrid.ShowEditValidationMessage method - it will display validation error message on top of the dialog, e.g.

JQGrid1.ShowEditValidationMessage("'Integer' must be > 100");

for details, please refer to the ASPX and C# code-behind files.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Trirand.Web.Mvc;
using System.Web.UI.WebControls;

namespace MVCDemo.Models
{
    public class EditValidationModel
    {
        public JQGrid ValidatedGrid { get; set; }

        public EditValidationModel()
        {
            ValidatedGrid = new JQGrid
                             {
                                 Columns = new List<JQGridColumn>()
                                 {
                                     new JQGridColumn { DataField = "Key", Visible = false, PrimaryKey = true },
                                     new JQGridColumn { DataField = "Integer", Width = 75, Editable = true },
                                     new JQGridColumn { DataField = "Number", Width = 100, Editable = true },
                                     new JQGridColumn { DataField = "Email", Editable = true },
                                     new JQGridColumn { DataField = "Link", Editable = true },
                                     new JQGridColumn { DataField = "Custom", Editable = true }
                                 },
                                 Width = Unit.Pixel(675)                                                                  
                             };
            ValidatedGrid.ToolBarSettings.ShowEditButton = true;
            ValidatedGrid.EditDialogSettings.CloseAfterEditing = true;          
            
        }
    }
}
@model MVCDemo.Models.EditValidationModel
@using Trirand.Web.Mvc
@using MVCDemo.Models

<!DOCTYPE html>
<html lang="en-us">
<head>
    <meta charset="utf-8">
    <title>jqGrid for ASP.NET MVC - server-side validation on edit</title>
    <!-- jQuery runtime minified -->
    <script src="~/Scripts/jquery-3.2.1.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/1.12.1/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.ValidatedGrid, "JQGrid1")
    </div>
    <br /><br />
    <div>
                  
    </div>    
    
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Text.RegularExpressions;
using MVCDemo.Models;
using Trirand.Web.Mvc;
using System.Web.UI.WebControls;

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

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

        public void SetUpGrid_EditServerSideValidation(JQGrid grid)
        {            
            // Setting the DataUrl to an action (method) in the controller is required.
            // This action will return the data needed by the grid.
            // EditUrl will point to the editing action
            grid.DataUrl = Url.Action("EditServerSideValidation_DataRequested");
            grid.EditUrl = Url.Action("EditServerSideValidation_EditRow");                   
        }

        // This method is called when the grid requests data. You can choose any method to call
        // by setting the JQGrid.DataUrl property
        public JsonResult EditServerSideValidation_DataRequested()
        {
            // Get both the grid Model
            // The data model in our case is an autogenerated linq2sql database based on Northwind.
            var gridModel = new EditValidationModel();
            SetUpGrid_EditServerSideValidation(gridModel.ValidatedGrid);

            // 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
            List<ServerValidatedEmployee> employees = GetServerValidatedEmployeeData();
            return gridModel.ValidatedGrid.DataBind(employees.AsQueryable());
        }

        public ActionResult EditServerSideValidation_EditRow(ServerValidatedEmployee editedEmployee)
        {
            // Get the grid and database (northwind) models
            var grid = new EditValidationModel().ValidatedGrid;
            var northWindModel = new NorthwindDataContext();           

            // If we are in "Edit" mode
            if (grid.AjaxCallBackMode == AjaxCallBackMode.EditRow)
            {
                string validationMessage = ValidateRowData(editedEmployee);
                if (!String.IsNullOrEmpty(validationMessage))
                    return grid.ShowEditValidationMessage(validationMessage);

                // Get the data from and find the Order corresponding to the edited row
                List<ServerValidatedEmployee> gridData = GetServerValidatedEmployeeData();
                ServerValidatedEmployee employeeToUpdate = gridData.Single<ServerValidatedEmployee>(e => e.Key == editedEmployee.Key);

                // Update the Employee information to match the edited Employee data
                // 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
                employeeToUpdate.Custom = editedEmployee.Custom;
                employeeToUpdate.Email = editedEmployee.Email;
                employeeToUpdate.Integer = editedEmployee.Integer;
                employeeToUpdate.Link = editedEmployee.Link;
                employeeToUpdate.Number = editedEmployee.Number;
                Session["ServerValidationDataSource"] = gridData;                
                // This will save the changes into the database. We have commented this since this is just an online demo
                // northWindModel.SubmitChanges();
            }

            return new RedirectResult(Url.Action("EditServerSideValidation_DataRequested", "grid"));
        }

        private string ValidateRowData(ServerValidatedEmployee employee)
        {   
            //valide the "Integer" edit field for Integer, Min(100) and Max(1000) values            
            if (employee.Integer == null)
                return "Integer column requires integer values.";
            if (employee.Integer < 100)            
                return "'Integer' must be > 100";
            if (employee.Integer > 1000)
                return "'Integer' must be < 1000";
           
            // valide the "Number" edit field for Decimal, Min(100.00) and Max(1000.00) values
            if (employee.Number == null)
                return "'Number' requires number values";
            if (employee.Number < 100)
                return "'Number' must be > 100.00";
            if (employee.Number > 1000)
                return "'Number' must be < 1000.00";            

            // validate the "Email" field for email validity
            string emailRegex = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}" +
                                     @"\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\" +
                                     @".)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";
            Regex re = new Regex(emailRegex);
            if (!re.IsMatch(employee.Email))
                return "'Email' is not in valid format.";

            // validate the "Url" field for URL validity
            string urlegex = "^(https?://)"
                    + "?(([0-9a-z_!~*'().&=+$%-]+: )?[0-9a-z_!~*'().&=+$%-]+@)?" //user@ 
                    + @"(([0-9]{1,3}\.){3}[0-9]{1,3}" // IP- 199.194.52.184 
                    + "|" // allows either IP or domain 
                    + @"([0-9a-z_!~*'()-]+\.)*" // tertiary domain(s)- www. 
                    + @"([0-9a-z][0-9a-z-]{0,61})?[0-9a-z]\." // second level domain 
                    + "[a-z]{2,6})" // first level domain- .com or .museum 
                    + "(:[0-9]{1,4})?" // port number- :80 
                    + "((/?)|" // a slash isn't required if there is no file name 
                    + "(/[0-9a-z_!~*'().;?:@&=+$,%#-]+)+/?)$";
            re = new Regex(urlegex);
            if (!re.IsMatch(employee.Link))
                return "'Url' is not in valid format.";

            // Validate the custom field - only allow "red", "blue", "green" literals
            if (! (employee.Custom.ToLower().Equals("red") ||
                   employee.Custom.ToLower().Equals("blue") ||
                   employee.Custom.ToLower().Equals("green") ))
                return "'Custom' only supports 'red','blue' and 'green'";

            return "";
        }


        public class ServerValidatedEmployee
        {
            public int Key { get; set; }
            public int? Integer { get; set; }
            public double? Number { get; set; }            
            public string Email { get; set; }
            public string Link { get; set; }
            public string Custom { get; set; }
        }

        public List<ServerValidatedEmployee> GetServerValidatedEmployeeData()
        {
            List<ServerValidatedEmployee> list = new List<ServerValidatedEmployee>();

            if (Session["ServerValidationDataSource"] == null)
            {
                list.Add(new ServerValidatedEmployee
                {
                    Key = 1,
                    Integer = 20000,
                    Number = 40000000.34,
                    Email = "john.smith@yahoo.com",
                    Link = "http://www.yahoo.com",
                    Custom = "Red"
                });
                list.Add(new ServerValidatedEmployee
                {
                    Key = 2,
                    Integer = 1000,
                    Number = 460000.21,
                    Email = "justin.doe@gmail.com",
                    Link = "http://www.gmail.com",
                    Custom = "Green"
                });
                list.Add(new ServerValidatedEmployee
                {
                    Key = 3,
                    Integer = 134000,
                    Number = 5220.34,
                    Email = "deborah.long@hotmail.com",
                    Link = "http://www.hotmail.com",
                    Custom = "blue"
                });
            }
            else
            {
                list = Session["ServerValidationDataSource"] as List<ServerValidatedEmployee>;
            }

            return list;
        }
    }
}
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" />