将值绑定到控制器的组合框

Question

我正在尝试将值绑定到控制器中的组合框，我收到的错误是＆＃39; ControlColumn＆＃39;未定义的。

<md-select ng-model="selected.pdfControl" ng-change="changePdfControl(selected.pdfControl)" required ng-disabled="!pdfFile">
    <md-option ng-repeat="pdfControl in pdfControls" ng-value="pdfControl">{{pdfControl.ControlColumn}} - {{pdfControl.ControlText}}</md-option>
</md-select>

$scope.selected.pdfControl.ControlColumn = "Test";

当我从同一个事件绑定不同的值时，一切正常

<md-input-container>
    <input ng-model="pdfVertical" required name="pdfVertical">
</md-input-container>

$scope.pdfVertical = "1234";