ng-model不绑定到控制器

Question

我正在尝试将文本输入的值绑定到模型值，但值仍未定义...

HTML：

<div class="panel panel-default">
  <div class="panel-body">
    <form name=user-form class="form-horizontal" novalidate>
      <label for="firstname" class="col-sm-2 control-label">Firstname</label>
      <div class="col-sm-4">
        <input type="text" ng-model="ctrl.formData.firstname" name="firstname" class="form-control" placeholder="Firstname"/>
      </div>
      <div class="col-md-offset-2">
        <input type="submit" class="btn btn-primary" name="submit" value="Add" ng-click="ctrl.submit()">
      </div>
    </form>
  </div>
</div>

AngularJS：

angular.module('app', ['ngRoute']);

angular.module('app').config(function($routeProvider) {
  $routeProvider
    .when('/', {
      templateUrl: 'pages/main.html',
      controller: 'MainController',
      controllerAs: 'ctrl'
    })
    .when('/user', {
      templateUrl: 'pages/user.html',
      controller: 'UserController',
      controllerAs: 'ctrl'
    });
});

angular
  .module('app')
  .controller('UserController', ['$http', '$scope', function($http, $scope) {
    var self = this;
    self.formData = {};

    self.submit = function() {
      $http.post('http://localhost:50211/api/user/add',
      JSON.stringify(self.getUserData()))
      .success(function() {
        console.log('Success');
      })
      .error(function() {
        console.log('Failed');
      });
    };

    self.getUserData = function() {
      return {
        FirstName: self.formData.firstname
      };
    };

}]);

ajax请求的数据对象始终包含＆＃39; Firstname：undefined＆＃39;，我猜测我错过了一些简单但无法看到的东西。