ArgumentOutOfRangeException寫入模式

Question

當我試圖寫一個模型首次在我的視圖中使用：我第一次寫信給模型，我得到一個ArgumentOutOfRangeException。在第一次寫

收到錯誤數組：

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

不能使用_model.AddQuestAnswModel[c]因爲你永遠不添加任何項目到列表中。

取而代之的是，創建一個新的對象，並設置其值，然後將項目添加到列表中。

事情是這樣的：

AdditionalQuestionAnswerModel newItem = new AdditionalQuestionAnswerModel(); 

//set the values here to newItem 

_model.AddQuestAnswModel.Add(newItem); 

Answer 2

你首先實例列表

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

然後您嘗試訪問的第一個元素

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

不添加任何元素列表。

通過指數試圖訪問列表之前添加的元素，或者更簡單：

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

銥意味着你_model.AddQuestAnswModel在指定postition，並從你的代碼，我看有沒有項目_model.AddQuestAnswModel只用new List<AdditionalQuestionAnswerModel>()發起的，所以它不包含的項目（除非你在構造器這樣做）。

您需要填寫它像這樣：

_model.AddQuestAnswModel.Add(item);