Question

我有一个名为Category的自引用实体。类别可以具有一个或多个子类别。一个类别也可能没有孩子。

我已经制作了实体和映射，但我一直得到这个例外。

NHibernate.TransientObjectException：object引用未保存的瞬态实例 - 在刷新或保存之前保存瞬态实例将属性的级联操作设置为可以创建它的东西自动保存。

我是否在绘制映射部分时出错了？
是否可以一次保存所有父对象和子对象？任何帮助将不胜感激。

以下是代码

POCO

public class Category
{
    private ICollection<Topic> _topics;
    private ICollection<Category> _childCategory;
    private ICollection<Media> _media;
    private Category _parentCategory;

    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
    public virtual string Description { get; set; }
    public virtual bool IsActive { get; set; }

    public virtual Category ParentCategory
    {
        get { return _parentCategory ?? (_parentCategory = new Category()); }
        protected set { _parentCategory = value; }
    }

    public virtual ICollection<Category> ChildCategory
    {
        get { return _childCategory ?? (_childCategory = new List<Category>()); }
        protected set { _childCategory = value; }
    }


    public virtual void AddChild(Category childCategory)
    {
        childCategory.ParentCategory = this;
    }
}

映射

public class CategoryMapping : IAutoMappingOverride<Category>
{
    public void Override(AutoMapping<Category> mapping)
    {
        mapping.Map(c => c.Name).Length(30);
        mapping.Map(c => c.Description).Length(160);
        mapping.References(x => x.ParentCategory)
            .Cascade.None()
            .Column("ParentCategoryId");
        mapping.HasMany(x => x.ChildCategory)
            .Inverse().Cascade.All()
            .KeyColumn("ParentCategoryId");
    }
}

测试我正在创建父类和子类，并尝试一次保存所有类别。

public void CanSaveAllNewObjectGraphFromCategory() {
    #region Categories and Child
    var categories = new sq.Category()
    {
        Description = "Category1",
        IsActive = true,
        Name = "Categoy1"
    };

    var childCat = new List<sq.Category>() {
        new sq.Category(){
            Description = "ChildCategory1",
            IsActive = true,
            Name = "CCategoy1"
        },
        new sq.Category(){
            Description = "ChildCategory2",
            IsActive = true,
            Name = "CCategoy2"
        }
    };

    foreach (var item in childCat)
    {
        categories.AddChild(item);
    }
    #endregion

    using (var tx = _session.BeginTransaction())
    {
        _catRepo.AddNewCategory(categories);
        tx.Commit(); // Error occurs when commit is executed.
    }
}

Answer 1

您的错误消息为您提供了两个选项：

在刷新前保存瞬态实例
将属性的级联操作设置为使其自动保存的内容

第一个选项很简单：只需在提交事务之前保存每个实例

using (var tx = _session.BeginTransaction())
{
  foreach(var category in categories)
  {
     _session.SaveOrUpdate(category);
  }
  _catRepo.AddNewCategory(categories);
  tx.Commit(); 
}

Answer 2

我们需要指定参考文献的两面

public virtual void AddChild(Category childCategory)
{
    childCategory.ParentCategory = this;
    // add to collection as well
   _childCategory.Add(childCategory);
}

NHibernate中的自引用实体为对象引用提供了未保存的瞬态实例异常

2 个答案: