(function($, kendo) {
            $.extend(true, kendo.ui.validator, {
                rules: {
                    remote: function(input) {
                        var remoteAttr = input.attr("data-val-remote-url");
                        if (typeof remoteAttr === typeof undefined || remoteAttr === false) {
                            return true;
                        }

                        var isInvalid = true;
                        var data = {};
                        data[input.attr('name')] = input.val();

                        $.ajax({
                            url: remoteAttr,
                            mode: "abort",
                            port: "validate" + input.attr('name'),
                            dataType: "json",
                            type: input.attr("data-val-remote-type"),
                            data: data,
                            async: false,
                            success: function(response) {
                                isInvalid = response;
                            }
                        });
                        return !isInvalid;
                    }
                },
                messages: {
                    remote: function(input) {
                        return input.data('val-remote');
                    }
                }
            });
        })(jQuery, kendo);

  [Moon.Web.Validation.RemoteValidator("IsUserExist", "Admin", HttpMethod = "POST", ErrorMessage = "نام کاربری قبلا ثبت شده است.")]
        public string Username { get; set; }

  @Html.EditorFor(model => model.Username)
  @Html.ValidationMessageFor(model => model.Username)

  [HttpPost]
        public ActionResult IsUserExist(string Username)
        {
            if (userSerive.isUser(Username)) return Json(true); 
            return Json(false);
        }