Hi alya14,
Check the below example and modify your code accordingly.
Controller
public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View();
    }
    public JsonResult GetEmployees()
    {
        List<Employee> employees = new List<Employee>();
        employees.Add(new Employee { ID = 1, Name = "Nancy Davolio" });
        employees.Add(new Employee { ID = 2, Name = "Andrew Fuller" });
        employees.Add(new Employee { ID = 3, Name = "Janet Leverling" });
        employees.Add(new Employee { ID = 4, Name = "Margaret Peacock" });
        return Json(employees, JsonRequestBehavior.AllowGet);
    }
    public JsonResult GetSelectedEmployees(List<Employee> employees)
    { 
        return Json(employees);
    }
    public class Employee
    {
        public int ID { get; set; }
        public string Name { get; set; }
    }
}
View
@{
    Layout = null;
}
<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
    <link rel="stylesheet" href="https://kendo.cdn.telerik.com/2020.1.114/styles/kendo.default-v2.min.css" />
    <script type="text/javascript" src="https://code.jquery.com/jquery-1.12.4.min.js"></script>
    <script type="text/javascript" src="https://kendo.cdn.telerik.com/2020.1.114/js/angular.min.js"></script>
    <script type="text/javascript" src="https://kendo.cdn.telerik.com/2020.1.114/js/kendo.all.min.js"></script>
    <script type="text/javascript">
        $(function () {
            $("#tblEmployees").kendoGrid({
                dataSource: {
                    transport: { read: "/Home/GetEmployees/" },
                    pageSize: 5
                },
                pageable: { refresh: true, pageSizes: [2, 25, 50] },
                groupable: false,
                sortable: true,
                persistSelection: true,
                columns: [
                    { selectable: true, width: 10 },
                    { field: "ID", title: "ID", width: 20 },
                    { field: "Name", title: "Name", width: 30 }
                ]
            });
            $('#btnCheckedRows').on('click', function () {
                var grid = $("#tblEmployees").data("kendoGrid");
                var selected = [];
                grid.select().each(function () {
                    selected.push(grid.dataItem(this));
                });
                $.ajax({
                    type: "POST",
                    url: "/Home/GetSelectedEmployees",
                    data: JSON.stringify(selected),
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function (r) {
                        alert(r + " record(s) inserted.");
                    }
                });
            });
        });
    </script>
</head>
<body>
    <div id="tblEmployees"></div><br /><br />
    <input type="button" id="btnCheckedRows" value="Get Checked Rows" />
</body>
</html>
Screenshots
KendoGrid with selected rows

Selected rows in Controller
