NHibernate错误消息：对象引用未保存的瞬态实例 - 在刷新之前保存瞬态实例

Question

我正在使用nHibernate并尝试添加一些主细节数据。数据库图表附在此处。

以下是添加类别和两个产品的代码：

//Category
namespace Sample.CustomerService.Domain
{

    public class Category {
        public Category() {
            Products = new List<Product>();
        }
        public virtual int CategoryID { get; set; }
        public virtual IList<Product> Products { get; set; }
        public virtual string Name { get; set; }
        public virtual string Unit { get; set; }

        public virtual void AddProduct(Product product)
        {
            Products.Add(product);
        }
    }
}

//CategoryMap
namespace Sample.CustomerService.Domain
{

    public class CategoryMap : ClassMap<Category> {

        public CategoryMap() {
            Table("Category");
            LazyLoad();
            Id(x => x.CategoryID).GeneratedBy.Identity().Column("CategoryID");
            Map(x => x.Name).Column("Name").Not.Nullable().Length(50);
            Map(x => x.Unit).Column("Unit").Not.Nullable().Length(3);
            HasMany(x => x.Products).KeyColumn("CategoryID");
        }
    }
}

//--------------------------------------------------------------------------------------------
//Product
namespace Sample.CustomerService.Domain
{

    public class Product {
        public Product() {
        }
        public virtual int ProductID { get; set; }
        public virtual Category Category { get; set; }
        public virtual string Name { get; set; }
        public virtual decimal UnitPrice { get; set; }

    }
}

//ProductMap
namespace Sample.CustomerService.Domain {


    public class ProductMap : ClassMap<Product> {

        public ProductMap() {
            Table("Product");
            LazyLoad();
            Id(x => x.ProductID).GeneratedBy.Identity().Column("ProductID");
            References(x => x.Category).Column("CategoryID");
            Map(x => x.Name).Column("Name").Not.Nullable().Length(50);
            Map(x => x.UnitPrice).Column("UnitPrice").Not.Nullable();
        }
    }
}

//----------------------------------------------------------------------------------------------
//Program
namespace WindowsHibernateTest
{
    public partial class TestClass : Form
    {
        public TestClass()
        {
            InitializeComponent();
            CreateNewProduct();
        }

        public void CreateNewProduct()
        {
            try
            {
                var sessionFactory = CreateSessionFactory();
                using (var session = sessionFactory.OpenSession())
                {
                    using (var sqlTrans = session.BeginTransaction())
                    {
                        Category newGold = new Category() { Name = "Gold", Unit = "GRM" };

                        Product ngOrn = new Product() { Name = "Bangles", UnitPrice = 1000.10M };
                        Product ogOrn = new Product() { Name = "Rings", UnitPrice = 2000.10M };

                        AddProductsToCategory(newGold, ngOrn, ogOrn);

                        session.SaveOrUpdate(newGold);

                        sqlTrans.Commit();
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        private static ISessionFactory CreateSessionFactory()
        {
            return Fluently.Configure().Database(MsSqlConfiguration.MsSql2005.
                ConnectionString("Data Source=MyDB; Initial Catalog=NHibernateTest; Trusted_Connection=true;")).Mappings(m => m.FluentMappings.AddFromAssemblyOf<Program>()).BuildSessionFactory();

        }

        public static void AddProductsToCategory(Category category, params Product[] products)
        {
            foreach (var product in products)
            {
                category.AddProduct(product);
            }
        }

    }
}

在第sqlTrans.Commit()行中，我收到以下错误：

  

对象引用未保存的瞬态实例 - 保存瞬态   冲洗前的实例。类型：Sample.CustomerService.Domain.Product，   实体：Sample.CustomerService.Domain.Product

我已经谷歌搜索了一段时间，并没有得到令人信服的解决方案。我已尝试this，this和this，但无法解决此错误。请帮我解决这个错误。提前谢谢。

Answer 1

我认为您需要在保存类别之前保存产品，因为您在HasMany上没有Cascade。 您需要更改添加产品方法以保持关系

foreach (var product in products)
{
    category.AddProduct(product); 
    product.Category = category;
}