写入模型时出现ArgumentOutOfRangeException

Question

我正在尝试首次在模型中使用模型：在我第一次写入模型时，我得到了ArgumentOutOfRangeException 。

第一次写入数组时出现错误：

private IAdditionalQuestionsService _service;
private SelectedAdditionalQuestionAnswerModel _model;
private void InitializeController()
{
    _service = GetObject<IAdditionalQuestionsService>();
    //GetPageHeaderText(inst);
    ViewBag.GetPageTitle = "Additional Questions";
}

[HttpGet]
public virtual ActionResult Edit()
{
    Institution inst = _service.GetInstitution(State.GetInstitutionRecordId());
    _model = GetObject<SelectedAdditionalQuestionAnswerModel>();
    _model.AddQuestAnswModel = new List<AdditionalQuestionAnswerModel>();
    GetPageConfiguration1(inst);
    return View(_model);
}

AdditionalQuestionAnswerModel m = GetObject<AdditionalQuestionAnswerModel>();
int c = 0;
foreach (var x in inst.AdditionalQuestions)
{
    foreach (var y in x.AdditionalQuestionAnswers)
    {
        // Error is happening on next line *************
        _model.AddQuestAnswModel[c].QuestionText = x.QuestionText;
        _model.AddQuestAnswModel[c].InstitutionId = x.InstitutionId;
        _model.AddQuestAnswModel[c].AdditionalQuestionId = x.Id;
        _model.AddQuestAnswModel[c].AnswerText = y.AnswerText;
        _model.AddQuestAnswModel[c].IsSelected = false;
        c++;
    }
}

Answer 1

您不能使用_model.AddQuestAnswModel[c]因为您从未将任何项目添加到列表中。

而是创建一个新对象并设置其值，然后将该项目添加到列表中。

像这样：

AdditionalQuestionAnswerModel newItem = new AdditionalQuestionAnswerModel();

//set the values here to newItem

_model.AddQuestAnswModel.Add(newItem);

Answer 2

您首先实例化您的列表

_model.AddQuestAnswModel = new List<AdditionalQuestionAnswerModel>();

然后您尝试访问第一个元素

_model.AddQuestAnswModel[c] // c == 0

而不向列表添加任何元素。

在尝试通过索引或更简单的方式访问列表之前，添加一个元素：

foreach (var y in x.AdditionalQuestionAnswers)
{
    AdditionalQuestionAnswerModel newObj = new AdditionalQuestionAnswerModel
    {
         QuestionText = x.QuestionText;
         InstitutionId = x.InstitutionId;
         AdditionalQuestionId = x.Id;
         AnswerText = y.AnswerText;
         IsSelected = false;
    };

    _model.AddQuestAnswModel.Add(newObj);
}

Answer 3

Ir表示_model.AddQuestAnswModel在指示的_model.AddQuestAnswModel上没有项目，并且从您的代码中，我看到_model.AddQuestAnswModel仅用new List<AdditionalQuestionAnswerModel>()初始化，因此它不包含任何项目（除非您重新在构造器中执行此操作）。

您需要像这样填充它：

_model.AddQuestAnswModel.Add(item);