Controller:

    public class CustomerController : Controller
    {
        private readonly ApplicationDbContext _dbcontext;
        public CustomerController(ApplicationDbContext applicationDbContext)
        {
            _dbcontext = applicationDbContext;
        }
        public IActionResult Index()
        {
            return View(_dbcontext.Customers.Select(c=> new CustomerViewModel() { Name=c.CustomerName, Descriptsion=c.Description}).ToList());
        }

        [HttpPost]
        public IActionResult Create(CustomerViewModel model)
        {
            if (ModelState.IsValid)
            {
                _dbcontext.Customers.Add(new Customer() { CustomerName = model.Name, Description = model.Descriptsion });
                _dbcontext.SaveChanges();
            }
            //after create new item, requery the database and return the CustomerList partial view to update the list.
            return PartialView("_CustomerListPV", _dbcontext.Customers.Select(c => new CustomerViewModel() { Name = c.CustomerName, Descriptsion = c.Description }).ToList());
        }
    }

Index:

    @model List<WebApplication6.Models.CustomerViewModel>

    @{
        ViewData["Title"] = "Index";
    }
  
    <div id="itemlist"> 
    <partial name="_CustomerListPV" model="@Model"></partial>
    </div>

    <div class="row">
        <div class="col-md-4"> 
                <div class="form-group">
                    <label  for="Name" class="control-label">Name</label>
                    <input name="Name" id="txtname" class="form-control" /> 
                </div>
                <div class="form-group">
                    <label for="Descriptsion" class="control-label">Description</label>
                    <input Name="Descriptsion" id="txtDescription" class="form-control" /> 
                </div>
                <div class="form-group">
                    <input type="button" id="addBtn" value="Add New Customer" class="btn btn-primary" />
                </div> 
        </div>
    </div>

    @section Scripts{
        <script>
            $(function () {
                $("#addBtn").click(function () {
                    var CustomerViewModel = {}; //create an object
                    CustomerViewModel.Name = $("#txtname").val();
                    CustomerViewModel.Descriptsion = $("#txtDescription").val();

                    $.ajax({
                        url: "@Url.Action("Create","Customer")",
                        data: { model: CustomerViewModel }, //the name ("model") should be the same with the parameter's name in the controller.
                        type: "Post", //change the method to Post.
                        success: function (result) {
                            $("#itemlist").html("");
                            $("#itemlist").html(result);
                        },
                        error: function (result) {
                            window.alert("This is an unhandled exception. ");
                        }
                    });
                });
            });
        </script>
    }

_CustomerListPV

    @model List<WebApplication6.Models.CustomerViewModel>

    <p>
        <a asp-action="Create">Create New</a>
    </p>
    <table class="table">
        <thead>
            <tr>
                <th>
                   Name
                </th>
                <th>
                   Description
                </th>
                <th></th>
            </tr>
        </thead>
        <tbody>
            @if(Model != null && Model.Count > 0){ 
                foreach (var item in Model) {
                    <tr>
                        <td>
                            @Html.DisplayFor(modelItem => item.Name)
                        </td>
                        <td>
                            @Html.DisplayFor(modelItem => item.Descriptsion)
                        </td>
                        <td>
                            @Html.ActionLink("Edit", "Edit", new { /* id=item.PrimaryKey */ }) |
                            @Html.ActionLink("Details", "Details", new { /* id=item.PrimaryKey */ }) |
                            @Html.ActionLink("Delete", "Delete", new { /* id=item.PrimaryKey */ })
                        </td>
                    </tr>
                }
            }
            else{
                <tr>
                    <td colspan="2">Empty</td>
                </tr>
            }
        </tbody>
    </table>