c# – 无法将值NULL插入列,表;列不允许空值. INSERT失败

发布时间：2020-12-15 22:04:55 所属栏目：百科来源：网络整理

导读：我在SO上发现了许多类似的问题,我尝试过所说的解决方案,但没有一个对我有用,有人能告诉我下面的代码有什么问题,需要做些什么修正才能使它可行： Models: public class ParentDataClassData { public ParentDataClassData() { TitleSetTitles = new ListChild

我在SO上发现了许多类似的问题,我尝试过所说的解决方案,但没有一个对我有用,有人能告诉我下面的代码有什么问题,需要做些什么修正才能使它可行：

Models:

public class ParentDataClassData
    {
        public ParentDataClassData()
        {
            TitleSetTitles = new List<ChildDataClass1>();
            TitlesSetEvents = new List<ChildDataClass2>();
        }

        public virtual int TitleSetID { get; set; }
        public virtual string Name { get; set; }
        public virtual IList<ChildDataClass1> TitleSetTitles { get; set; }

        public virtual IEnumerable<ChildDataClass2> TitlesSetEvents { get; set; }

        public virtual object IdentityField
        {
            get { return TitleSetID; }
        }
    }


public class ChildDataClass1
    {
        public ChildDataClass1()
        {
            TitleSet = new ParentDataClassData();
            TitleSetTitleEventMedias = new List<TitleSetTitleEventMediaData>();
        }

        public virtual int TitleSetID
        {
            get { return TitleSet.TitleSetID; }
        }

        public virtual ParentDataClassData TitleSet { get; set; }

        public virtual IList<TitleSetTitleEventMediaData> TitleSetTitleEventMedias { get; set; }

        public virtual object IdentityField
        {
            get { return TitleSetTitleID; }
        }

    }


 public class ChildDataClass2
    {
        public virtual ParentDataClassData TitleSet { get; set;  }

        public virtual int TitleSetEventID
        {
            get;
            set;
        }


        public virtual object IdentityField
        {
            get { return TitleSetEventID; }
        }
    }

Mappings:

public class ParentDataClassMap : ClassMap<ParentDataEntity>
    {
        public ParentDataClassMap()
        {
            Table("TitleSet");

            LazyLoad();

            Id(x => x.TitleSetID)
                .Column("TitleSetID")
                .GeneratedBy.Native()
                .UnsavedValue(0);


            HasMany(x => x.TitleSetTitles)
            .LazyLoad()
            .Inverse()
            .Fetch.Subselect()
            .Cascade.SaveUpdate()
            .KeyColumn("TitleSetID");

            HasMany(x => x.TitlesSetEvents)
                .LazyLoad()
                .Inverse()
                .Cascade.SaveUpdate()
                .Fetch.Subselect()
                .KeyColumn("TitleSetID");
        }
    }


 public class ChildDataClass1Map : ClassMap<ChildDataClass1>
    {
        public ChildDataClass1Map()
        {
            Table("TitleSetTitle");

            Id(x => x.TitleSetTitleID)
                .Column("TitleSetTitleID")
                .GeneratedBy.Native()
                .UnsavedValue(0);

            References(x => x.TitleSet)
                .Fetch.Join()
                .Not.Nullable()
                .Column("TitleSetID")
                .Cascade.None();


            HasMany(x => x.TitleSetTitleEventMedias)
                .LazyLoad()
                .Inverse()
                .Cascade.AllDeleteOrphan()
                .Fetch.Subselect()
                .KeyColumn("TitleSetTitleID");
        }
}


 public class ChildDataClass2Map : ClassMap<ChildDataClass2>
    {
        public ChildDataClass2Map()
        {
            Table("TitleSetEvent");

            Id(x => x.TitleSetEventID)
                .Column("TitleSetEventID")
                .GeneratedBy.Native()
                .UnsavedValue(0);


            References(x => x.TitleSet)
                .Column("TitleSetID")
                .Not.Update()
                .Not.Insert()
                .Cascade.None();

            Map(x => x.LengthSec).Not.Nullable();
            Map(x => x.EventID).Not.Nullable();

            HasMany(x => x.TitleSetDefaultEventMedia)
                .LazyLoad()
                .Inverse()
                .Cascade.None()
                .Fetch.Join()
                .KeyColumn("TitleSetEventID");

            HasMany(x => x.TitleSetTitleEventMedias)
                .LazyLoad()
                .Inverse()
                .Cascade.None()
                .Fetch.Join()
                .KeyColumn("TitleSetEventID");
        }
    }

Test:

[Test]
        public void CanAddNewTitleSet()
        {
            var titleSet = new TitleSetDataEntity
                {
                    Name = "Somename",ProgramServiceID = 1,CreatedBy = "someuser",CreatedDate = DateTime.Now,ModifiedBy = "someuser",ModifiedDate = DateTime.Now,TitleSetTitles = new List<TitleSetTitleData>
                    {
                        new TitleSetTitleData
                        {
                            IsIncluded = true,IsPremiere = true,TitleTypeCode = "somecode",}
                    },TitlesSetEvents = new List<TitleSetEventData>()
                };


                Session.SaveOrUpdate(titleSet);

            }

并获得例外：

NHibernate.AdoNet.AbstractBatcher: ERROR
NHibernate.AdoNet.AbstractBatcher [(null)] – Could not execute query:
INSERT INTO TitleSetTitle ([TitleID],…,TitleSetID) VALUES (@p0,
@p1,@p2,@p3,@p4,@p5,@p6,@p7,@p8); select SCOPE_IDENTITY()
System.Data.SqlClient.SqlException (0x80131904): Cannot insert the
value NULL into column ‘TitleSetID’,table ‘TitleSetTitle’; column
does not allow nulls. INSERT fails. The statement has been terminated.

附：

>我使用逆向双向映射
>无论如何逆不遵守这些事情,根据我的理解,它应首先保存ParantClassData以确保Child类获得正确的ID.
>不确定,我错过了什么

任何有关上述问题的帮助将受到热烈的赞赏！

更新
添加了更多信息来解释问题,而不是冗长的代码,我只是想知道无论如何TitleSetID readonly属性相关的问题.

解决方法

实际上这个问题隐藏在这个映射中：

HasMany(x => x.TitleSetTitles)
    ...
    .Inverse();

这个映射正在指导NHibernate：

The chlild will care about this relation.

但这意味着,那个孩子必须知道它的父母.在此代码中不是这样的：

var titleSet = new TitleSetDataEntity
{
    Name = "Somename",...
    TitleSetTitles = new List<TitleSetTitleData>
    {
        new TitleSetTitleData...
    },};
session.Save(titleSet);

在此代码中,由新TitleSetTitleData创建的子实例缺少父引用！这就是问题所在

注 – 我猜属性TitleSetTitles属于IList< ChildDataClass1>类型. TitleSetTitles但在代码中我们使用新的List< TitleSetTitleData> ……我猜这是一个错字

正确的语法是：

var titleSet = new TitleSetDataEntity
{
    Name = "Somename",...
    TitleSetTitles = new List<TitleSetTitleData>();
};
var child = new TitleSetTitleData
{
    ...
    ParentDataClassData = titleSet,};
titleSet.TitleSetTitles.Add(child);
session.Save(titleSet);

而现在,NHibernate将拥有足够的信息. Parent在列表中添加了一个Child,Child知道Parent和.Inverse()映射将起作用,因为Parent的ID不再为null

（编辑：李大同）

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