AngularJS-TypeError：使用下拉菜单时，无法读取未定义的属性“名称”

Question

 <select id="ddlPropertyName" ng-options="property.Name for property in allProperty" ng-model="property.Name"><option value="">-Select Name-</option>
                            </select>

如果no value selected in dropdown我将出现以下错误:( TypeError：无法读取未定义的属性“名称””

js代码名称：$ scope.property.Name.Name

但是我想如果仍然没有选择任何值，我可以检查undefined或null，以便我的Json可以设置值并执行代码而无需执行

Answer 1

使用其他模型变量代替property 。 在这里，在修改后的HTML中，我使用了selectedProperty

<select id="ddlPropertyName" 
    ng-options="property.Name for property in allProperty" 
    ng-model="selectedProperty">
    <option value="">-Select Name-</option>
</select>

注意：您正在ngOption中使用label for value in array中label for value in array因此selectedProperty将保存property类型

Answer 2

以下代码对我有用

  <select ng-model="qid">
            <option value="">--Select--</option>
     <option ng-repeat="p in pollquestions" value="{{p.QId}}">{{p.QText}}</option>
 </select>

 app.controller("optionsCntrl", function ($scope, angularService) {
//$scope.optionsCntrl = [{ QId: 1, QText: "What is this 1?" }];
var getData = angularService.getQuestion();
getData.then(function (ques) {
    $scope.pollquestions = ques.data;
}, function () {
    alert('Error in getting records');
});
$scope.AddUpdatePollQuestionOption = function () {
    var pollquestionanswer = {
        qid:$scope.qid,
        anstext: $scope.anstext,
        anscount: 1
    };
    var getData = angularService.addPollQuestionOptions(pollquestionanswer).success(deferred.resolve).error(deferred.reject);
    getData.then(function (msg) {
        alert(msg.data);
    }, function () {
        alert('Error in adding record');
    });
}
});
 public string AddPollQuestionOptions(PollQuestionAnswer pollQuestionAnswer)
    {
        if (pollQuestionAnswer != null)
        {
            if (!String.IsNullOrEmpty(Convert.ToString(pollQuestionAnswer.qid)))
            {
                try
                {
                    using (DemoContext contextObj = new DemoContext())
                    {
                        contextObj.pollquestionanswer.Add(pollQuestionAnswer);
                        contextObj.SaveChanges();
                        return "Poll Question Answer Added";
                    }
                }
                catch (Exception objEx)
                {
                    return "Poll Question Not Found";
                }
            }
            else
            {
                return "Invalid Request";
            }
        }
        else
        {
            return "Invalid Record";
        }

    }

Answer 3

当您在“列定义”中指定的字段没有名称或同一列两次被放入“列定义”时，基本上会发生此错误。 搜索相似的列，并删除具有相同名称的列，以解决此错误。

Answer 4

只需在控制器中使用以下代码

if($scope.property.Name !== null || $scope.property.Name !== undefined) {
    console.log('here');
}