Javascript 无法在angular js材质设计中绑定数据

我正在尝试用angular js材质设计对话框绑定数据。 但无法绑定

$scope.header

Html

---

如果有一个愚蠢的错误，我很抱歉。任何帮助都是值得的。谢谢，这确实是个愚蠢的错误。碰巧

更改行：

<h2 ng-model="header">{{$scope.header}}</h2>

{{$scope.header}

致：

{{header}

谢谢。我必须停止相信我的能力。

 angular.module('MyApp',['ngMaterial', 'ngMessages', 'material.svgAssetsCache'])

.controller('AppCtrl', function($scope, $mdDialog, $mdMedia) {
  $scope.status = '  ';
  $scope.customFullscreen = $mdMedia('xs') || $mdMedia('sm');

  
$scope.showAdvanced = function(ev) {
    var useFullScreen = ($mdMedia('sm') || $mdMedia('xs'))  && $scope.customFullscreen;

    $mdDialog.show({
      controller: DialogController,
      templateUrl: 'dialog1.tmpl.html',
      parent: angular.element(document.body),
      targetEvent: ev,
      clickOutsideToClose:true,
      fullscreen: useFullScreen
    })
 };

  
});

function DialogController($scope, $mdDialog) {
  $scope.header="Mango";
  
  $scope.hide = function() {
    $mdDialog.hide();
  };

  $scope.cancel = function() {
    $mdDialog.cancel();
  };

  $scope.answer = function(answer) {
    $mdDialog.hide(answer);
  };
}

<h2 ng-model="header">{{$scope.header}}</h2>

<h2 ng-model="header">{{header}}</h2>