NHibernate 中的自引用实体给对象引用一个未保存的瞬态实例异常

Question

我有一个名为 Category 的自引用实体。一个类别可能有一个或多个子类别。类别也可能没有子项。

我已经制作了实体和映射，但我一直收到此异常。

NHibernate.TransientObjectException : object references an unsaved transient instance - save the transient instance before flushing or set cascade action for the property to something that would make it autosave.

我是不是映射部分有问题？
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。

代码如下

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别和子类别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

我们需要分配引用的两边

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

Answer 2

您的错误消息给了您两个选择：

刷新前保存临时实例
将属性的级联操作设置为可以自动保存的内容

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(); 
}

NHibernate 中的自引用实体给对象引用一个未保存的瞬态实例异常

Self referencing entity in NHibernate gives object references an unsaved transient instance exception

mapping

nhibernate

orm

fluent-nhibernate

fluent-nhibernate-mapping