<form id="form1" name="form1" ng-app="app" ng-controller="ctrl" novalidate>
  <input id="Text1" type="text" ng-model="Account" is-Administrator/>
  <br />
  <input id="ButtonVerify" type="button" value="Verify" ng-click="Verify();" />
 </form>

 @Scripts.Render("~/bundles/angular")

 var app = angular.module('app', []); 

app.controller('ctrl', function ($scope) {
   $scope.Account;
   $scope.Verify = function () {
    if ($scope.form1.$valid) {
     alert('OK.');
    }
    else {
     alert('failure.');
    }
   };
  });  

app.directive("isAdministrator", function ($q, $timeout) {
   var adminAccount = "Admin";
   var CheckIsAdministrator = function (account) {
    return adminAccount == account ? true : false;
   };
   return {
    restrict: "A",
    require: "ngModel",
    link: function (scope, element, attributes, ngModel) {
     ngModel.$asyncValidators.isAdministrator = function (value) {
      var defer = $q.defer();
      $timeout(function () {
       if (CheckIsAdministrator(value)) {
        defer.resolve();
       } else {
        defer.reject();
       }
      }, 700);
      return defer.promise;
     }
    }
   };
  });