Nhibernate多对多xml

Question

我想在Nhibernate中建立一个多对多的关系，但我现在卡住了，我有3个sql表，学生类和学生类关系，我已经用c#写了2个类。

class Student
{ 

        public virtual int StudentID { get; set; }

        public virtual string name { get; set; }

        public virtual IList<Class> Classes { get; set; }

        public virtual void AddClass(Class Classer) {

            Classes.Add(Classer);
        }

    }
    '''

class Class
{
    
        public virtual int ClassID { get; set; }

        public virtual string name { get; set; }
        public virtual string teacher { get; set; }
       
        public virtual List<Student> students { get; set; }

        public virtual void AddStudent(Student stud) {
            students.Add(stud);
         
        }
}

我的xml文件是这样的，另一个是一样的。

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="NHibernateTutorialPart1"
                   namespace="NHibernateTutorialPart1">

    <class name="Student">

        <id name="StudentID" column="StudentID" >
        
        </id>

        <property name="name" />
        
<bag name ="Classes" table="ClassStudentRelation" cascade ="all" inverse ="true" >
    <key column="ClassID"></key>
    <many-to-many class="Class"> </many-to-many>
    </bag>
    </class>

</hibernate-mapping>

在我的main中，我创建了这个对象

Student sven= new Student {StudentID=7,  name = "sven" };
Class Ai = new Class {ClassID=7, name = "AI", teacher = "lauer" };

List<Class> tmp = new List<Class>();
List<Student> save = new List<Student>();

save.Add(sven);
tmp.Add(Ai);

Student sven2= new Student { StudentID = 62, name = "sven2",Classes=tmp };
Class Ai2 = new Class { ClassID = 62, name = "AI2", teacher = "lauer2",students=save };

mySession.Save(sven2);
mySession.Save(Ai2);
mySession.Transaction.Commit();

如果我提交没有sven和ai没有列表，我能够提交的信息在正确的sql tabel，但我想提交ai2和sven2与其他的列表，我得到的信息到3个表，但这工作有人知道如何修复它。错误是与不匹配

NHibernate.Collection.Generic.PersistentGenericBag and NHibernate.Collection.Generic.PersistentGenericList

Answer 1

类包映射存在问题。假设ClassStudentRelation连接表具有StudentID和ClassID外键。映射应为：

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
               assembly="NHibernateTutorialPart1"
               namespace="NHibernateTutorialPart1">

<class name="Student">

    <id name="StudentID" column="StudentID" >        
    </id>

    <property name="name" />
    
<bag name="Classes" table="ClassStudentRelation" cascade="all" inverse="false">
    <key column="StudentID"></key>
    <many-to-many class="Class" column="ClassID" />
    </bag>
</class>

</hibernate-mapping>

inverse属性应设置为false，因为集合负责管理关系。

Class对象的映射如下所示：

​

<class name="Class">

    <id name="ClassID" column="ClassID" >        
    </id>

    <property name="name" />
    
<bag name="Students" table="ClassStudentRelation" cascade="all" inverse="false">
    <key column="ClassID"></key>
    <many-to-many class="Student" column="StudentID" />
    </bag>
</class>

</hibernate-mapping>

此外，您不能覆盖nhibernate实体中的集合。应该尽快初始化这些集合，然后就可以使用AddClass/AddStudent方法了。

class Student
{ 
...
public virtual IList<Class> Classes { get; set; } = new List<Class>();
...
}

Student sven2= new Student { StudentID = 62, name = "sven2" };
sven2.AddClass(Ai);
Ai.AddStudent(sven2);
mySession.Save(sven2);
mySession.Save(Ai);