非空属性引用空值或瞬态值

Question

我正在使用 NHibernate，但遇到了问题，因为尝试保存到数据库时会引发异常：

非空属性引用空值或瞬态值 NHibernate.Entities.Question.Test

我怎样才能改变它？

public class TestMap: ClassMap<Test>
{
    public TestMap()
    {
        Table("Test");

        Id(x => x.Id)
            .GeneratedBy.Identity()
            .Column("Id");

        Map(x => x.Name)
            .Column("Name")
            .Not.Nullable();

        HasMany(x => x.Question).KeyColumn("TestId")
         .Cascade.All()
        .Not.LazyLoad();
    }
}

public class QuestionMap: ClassMap<Question>
{
    public QuestionMap()
    {
        Table("Question");

        References(x => x.Test)
            .Column("TestId")
            .Not.Nullable()
            .Cascade.SaveUpdate()
            .Not.LazyLoad();

        Id(x => x.Id)
            .GeneratedBy.Identity()
            .Column("Id");

        Map(x => x.QuestionContent)
            .Column("QuestionContent")
            .Not.Nullable();

        HasMany(x => x.Answer)
            .KeyColumn("QuestionId")
            .Cascade.All()
        //.Cascade.SaveUpdate()
        .Not.LazyLoad();
    }
}

编辑：类

public class Question: Entity
{
    public Question()
    {
        Answer = new List<Answer>();
    }
    public virtual string QuestionContent { get; set; }
    public virtual IList<Answer> Answer { get; set; }
    public virtual Test Test { get; set; }

    public virtual void AddAnswer(Answer answer)
    {
        answer.Question = this;
        Answer.Add(answer);
    }
}

public class Test : Entity
{
    public Test()
    {
        Question = new List<Question>();
    }

    public virtual string Name { get; set; }
    public virtual IList<Question> Question { get; set; }

    public virtual void AddQuestion(List<Question> questions)
    {
        foreach (var question in questions)
        {
            question.Test = this;
            Question.Add(question);
        }
    }
}

问题有答案，答案有 GivenAnswer，GivenAnswer 有 SolvedTest。我不知道可能出了什么问题。

Answer 1

确保questionEntity 的Test 属性设置为映射为Not.Nullable()。