オブジェクトのシリアル化中に循環参照が検出されました。このエラーは何ですか？

Question

List<Question>オブジェクトをJSONデータにシリアル化したいと思います。

私が使用して私のASP.NET MVCアプリケーションでは、現在よコードは次のとおりです。

List<Question> questionList;    
      questionList = questionManager.GetquestionsByTestId(id); 
      var listData = questionList.ToArray(); 
      JavaScriptSerializer serializer = new JavaScriptSerializer(); 

      string strData = serializer.Serialize(listData); 

      JsonResult json = Json(strData, JsonRequestBehavior.AllowGet); 

コードは、次のエラーが発生しているようだ：

A circular reference was detected while serializing an object of type 'TestEnvironment.Models.Question'. 

このエラーがどうあるべきか手段 ？

編集：質問クラス

public partial class Question : INotifyPropertyChanging, INotifyPropertyChanged 
    { 

     private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty); 

     private int _QuestionId; 

     private string _QuestionText; 

     private System.Nullable<int> _TopicId; 

     private System.Nullable<int> _Marks; 

     private System.Nullable<int> _QuestionTypeId; 

     private System.Nullable<int> _ChapterId; 

     private System.Nullable<int> _Weightage; 

     private System.Nullable<System.TimeSpan> _ExpectedTimeToAnswer; 

     private EntitySet<Answer> _Answers; 

     private EntitySet<TestDetail> _TestDetails; 

     private EntityRef<Chapter> _Chapter; 

     private EntityRef<QuestionType> _QuestionType; 

     private EntityRef<Topic> _Topic; 

    #region Extensibility Method Definitions 
    partial void OnLoaded(); 
    partial void OnValidate(System.Data.Linq.ChangeAction action); 
    partial void OnCreated(); 
    partial void OnQuestionIdChanging(int value); 
    partial void OnQuestionIdChanged(); 
    partial void OnQuestionTextChanging(string value); 
    partial void OnQuestionTextChanged(); 
    partial void OnTopicIdChanging(System.Nullable<int> value); 
    partial void OnTopicIdChanged(); 
    partial void OnMarksChanging(System.Nullable<int> value); 
    partial void OnMarksChanged(); 
    partial void OnQuestionTypeIdChanging(System.Nullable<int> value); 
    partial void OnQuestionTypeIdChanged(); 
    partial void OnChapterIdChanging(System.Nullable<int> value); 
    partial void OnChapterIdChanged(); 
    partial void OnWeightageChanging(System.Nullable<int> value); 
    partial void OnWeightageChanged(); 
    partial void OnExpectedTimeToAnswerChanging(System.Nullable<System.TimeSpan> value); 
    partial void OnExpectedTimeToAnswerChanged(); 
    #endregion 

     public Question() 
     { 
      this._Answers = new EntitySet<Answer>(new Action<Answer>(this.attach_Answers), new Action<Answer>(this.detach_Answers)); 
      this._TestDetails = new EntitySet<TestDetail>(new Action<TestDetail>(this.attach_TestDetails), new Action<TestDetail>(this.detach_TestDetails)); 
      this._Chapter = default(EntityRef<Chapter>); 
      this._QuestionType = default(EntityRef<QuestionType>); 
      this._Topic = default(EntityRef<Topic>); 
      OnCreated(); 
     } 

     [Column(Storage="_QuestionId", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)] 
     public int QuestionId 
     { 
      get 
      { 
       return this._QuestionId; 
      } 
      set 
      { 
       if ((this._QuestionId != value)) 
       { 
        this.OnQuestionIdChanging(value); 
        this.SendPropertyChanging(); 
        this._QuestionId = value; 
        this.SendPropertyChanged("QuestionId"); 
        this.OnQuestionIdChanged(); 
       } 
      } 
     } 

     [Column(Storage="_QuestionText", DbType="NVarChar(MAX)")] 
     public string QuestionText 
     { 
      get 
      { 
       return this._QuestionText; 
      } 
      set 
      { 
       if ((this._QuestionText != value)) 
       { 
        this.OnQuestionTextChanging(value); 
        this.SendPropertyChanging(); 
        this._QuestionText = value; 
        this.SendPropertyChanged("QuestionText"); 
        this.OnQuestionTextChanged(); 
       } 
      } 
     } 

     [Column(Storage="_TopicId", DbType="Int")] 
     public System.Nullable<int> TopicId 
     { 
      get 
      { 
       return this._TopicId; 
      } 
      set 
      { 
       if ((this._TopicId != value)) 
       { 
        if (this._Topic.HasLoadedOrAssignedValue) 
        { 
         throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException(); 
        } 
        this.OnTopicIdChanging(value); 
        this.SendPropertyChanging(); 
        this._TopicId = value; 
        this.SendPropertyChanged("TopicId"); 
        this.OnTopicIdChanged(); 
       } 
      } 
     } 

     [Column(Storage="_Marks", DbType="Int")] 
     public System.Nullable<int> Marks 
     { 
      get 
      { 
       return this._Marks; 
      } 
      set 
      { 
       if ((this._Marks != value)) 
       { 
        this.OnMarksChanging(value); 
        this.SendPropertyChanging(); 
        this._Marks = value; 
        this.SendPropertyChanged("Marks"); 
        this.OnMarksChanged(); 
       } 
      } 
     } 

     [Column(Storage="_QuestionTypeId", DbType="Int")] 
     public System.Nullable<int> QuestionTypeId 
     { 
      get 
      { 
       return this._QuestionTypeId; 
      } 
      set 
      { 
       if ((this._QuestionTypeId != value)) 
       { 
        if (this._QuestionType.HasLoadedOrAssignedValue) 
        { 
         throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException(); 
        } 
        this.OnQuestionTypeIdChanging(value); 
        this.SendPropertyChanging(); 
        this._QuestionTypeId = value; 
        this.SendPropertyChanged("QuestionTypeId"); 
        this.OnQuestionTypeIdChanged(); 
       } 
      } 
     } 

     [Column(Storage="_ChapterId", DbType="Int")] 
     public System.Nullable<int> ChapterId 
     { 
      get 
      { 
       return this._ChapterId; 
      } 
      set 
      { 
       if ((this._ChapterId != value)) 
       { 
        if (this._Chapter.HasLoadedOrAssignedValue) 
        { 
         throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException(); 
        } 
        this.OnChapterIdChanging(value); 
        this.SendPropertyChanging(); 
        this._ChapterId = value; 
        this.SendPropertyChanged("ChapterId"); 
        this.OnChapterIdChanged(); 
       } 
      } 
     } 

     [Column(Storage="_Weightage", DbType="Int")] 
     public System.Nullable<int> Weightage 
     { 
      get 
      { 
       return this._Weightage; 
      } 
      set 
      { 
       if ((this._Weightage != value)) 
       { 
        this.OnWeightageChanging(value); 
        this.SendPropertyChanging(); 
        this._Weightage = value; 
        this.SendPropertyChanged("Weightage"); 
        this.OnWeightageChanged(); 
       } 
      } 
     } 

     [Column(Storage="_ExpectedTimeToAnswer", DbType="Time")] 
     public System.Nullable<System.TimeSpan> ExpectedTimeToAnswer 
     { 
      get 
      { 
       return this._ExpectedTimeToAnswer; 
      } 
      set 
      { 
       if ((this._ExpectedTimeToAnswer != value)) 
       { 
        this.OnExpectedTimeToAnswerChanging(value); 
        this.SendPropertyChanging(); 
        this._ExpectedTimeToAnswer = value; 
        this.SendPropertyChanged("ExpectedTimeToAnswer"); 
        this.OnExpectedTimeToAnswerChanged(); 
       } 
      } 
     } 

     [Association(Name="Question_Answer", Storage="_Answers", ThisKey="QuestionId", OtherKey="QuestionId")] 
     public EntitySet<Answer> Answers 
     { 
      get 
      { 
       return this._Answers; 
      } 
      set 
      { 
       this._Answers.Assign(value); 
      } 
     } 

     [Association(Name="Question_TestDetail", Storage="_TestDetails", ThisKey="QuestionId", OtherKey="QuestionId")] 
     public EntitySet<TestDetail> TestDetails 
     { 
      get 
      { 
       return this._TestDetails; 
      } 
      set 
      { 
       this._TestDetails.Assign(value); 
      } 
     } 

     [Association(Name="Chapter_Question", Storage="_Chapter", ThisKey="ChapterId", OtherKey="ChapterId", IsForeignKey=true)] 
     public Chapter Chapter 
     { 
      get 
      { 
       return this._Chapter.Entity; 
      } 
      set 
      { 
       Chapter previousValue = this._Chapter.Entity; 
       if (((previousValue != value) 
          || (this._Chapter.HasLoadedOrAssignedValue == false))) 
       { 
        this.SendPropertyChanging(); 
        if ((previousValue != null)) 
        { 
         this._Chapter.Entity = null; 
         previousValue.Questions.Remove(this); 
        } 
        this._Chapter.Entity = value; 
        if ((value != null)) 
        { 
         value.Questions.Add(this); 
         this._ChapterId = value.ChapterId; 
        } 
        else 
        { 
         this._ChapterId = default(Nullable<int>); 
        } 
        this.SendPropertyChanged("Chapter"); 
       } 
      } 
     } 

     [Association(Name="QuestionType_Question", Storage="_QuestionType", ThisKey="QuestionTypeId", OtherKey="QuestionTypeId", IsForeignKey=true)] 
     public QuestionType QuestionType 
     { 
      get 
      { 
       return this._QuestionType.Entity; 
      } 
      set 
      { 
       QuestionType previousValue = this._QuestionType.Entity; 
       if (((previousValue != value) 
          || (this._QuestionType.HasLoadedOrAssignedValue == false))) 
       { 
        this.SendPropertyChanging(); 
        if ((previousValue != null)) 
        { 
         this._QuestionType.Entity = null; 
         previousValue.Questions.Remove(this); 
        } 
        this._QuestionType.Entity = value; 
        if ((value != null)) 
        { 
         value.Questions.Add(this); 
         this._QuestionTypeId = value.QuestionTypeId; 
        } 
        else 
        { 
         this._QuestionTypeId = default(Nullable<int>); 
        } 
        this.SendPropertyChanged("QuestionType"); 
       } 
      } 
     } 

     [Association(Name="Topic_Question", Storage="_Topic", ThisKey="TopicId", OtherKey="TopicId", IsForeignKey=true)] 
     public Topic Topic 
     { 
      get 
      { 
       return this._Topic.Entity; 
      } 
      set 
      { 
       Topic previousValue = this._Topic.Entity; 
       if (((previousValue != value) 
          || (this._Topic.HasLoadedOrAssignedValue == false))) 
       { 
        this.SendPropertyChanging(); 
        if ((previousValue != null)) 
        { 
         this._Topic.Entity = null; 
         previousValue.Questions.Remove(this); 
        } 
        this._Topic.Entity = value; 
        if ((value != null)) 
        { 
         value.Questions.Add(this); 
         this._TopicId = value.TopicId; 
        } 
        else 
        { 
         this._TopicId = default(Nullable<int>); 
        } 
        this.SendPropertyChanged("Topic"); 
       } 
      } 
     } 

     public event PropertyChangingEventHandler PropertyChanging; 

     public event PropertyChangedEventHandler PropertyChanged; 

     protected virtual void SendPropertyChanging() 
     { 
      if ((this.PropertyChanging != null)) 
      { 
       this.PropertyChanging(this, emptyChangingEventArgs); 
      } 
     } 

     protected virtual void SendPropertyChanged(String propertyName) 
     { 
      if ((this.PropertyChanged != null)) 
      { 
       this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); 
      } 
     } 

     private void attach_Answers(Answer entity) 
     { 
      this.SendPropertyChanging(); 
      entity.Question = this; 
     } 

     private void detach_Answers(Answer entity) 
     { 
      this.SendPropertyChanging(); 
      entity.Question = null; 
     } 

     private void attach_TestDetails(TestDetail entity) 
     { 
      this.SendPropertyChanging(); 
      entity.Question = this; 
     } 

     private void detach_TestDetails(TestDetail entity) 
     { 
      this.SendPropertyChanging(); 
      entity.Question = null; 
     } 
    } 

Answer 1

それはかなりそれが言うことを意味します。

循環参照とは、クラスが直列化可能なプロパティ内で自身への参照を持つことを意味します。

質問クラスに質問タイプのプロパティがあると思いますか？ JSON-Serializerはこれを残念ながらシリアル化できません..

独自のシリアライザを作成しようとする可能性がありますが、最も簡単な解決策は、そのプロパティを別のクラスに変更することです。

これが間違っている場合は、ご質問に質問クラスのコードを投稿してください。