流畅的nHibernate映射HasMany到实体/表没有主键

我在尝试建立一个由没有主键的表支持的实体的HasMany关系时遇到了最严重的问题。

ClassA有一个CompositeId。为了避免ClassB上缺少primary key，我尝试在ClassB上创建包含表中所有列的CompositeId。不管我怎么努力，都没有用。

这些是我的类和映射。

public class ClassA
{
    public virtual int a_1_id {get;set;}
    public virtual string a_2_id {get;set;}
    public virtual IList<classB> ClassBs { get; set; }
    public override int GetHashCode()
    {
        int hashCode = 0;
        hashCode = hashCode ^ a_1_id ^ a_2_id.GetHashCode();
        return hashCode;
    }
    public override bool Equals(object obj)
    {
        var toCompare = obj as ClassB;
        return (toCompare != null) && (this.GetHashCode() != toCompare.GetHashCode());
    }
}
public class ClassAMap : ClassMap<ClassA>
{
    public ClassAMap()
    {
        Schema("dbo");
        Table("ClassA");
        Not.LazyLoad();
        CompositeId()           
            .KeyProperty(x => x.a_1_id, "a_1_id")
            .KeyProperty(x => x.a_2_id, "a_2_id");      
        HasMany(x => x.ClassBs)
            .Table("ClassB")
            .KeyColumn("a_2_id")
            .Not.LazyLoad();
    }
}
public class ClassB
{
    public virtual string a_2_id {get;set;}
    public virtual string b_field1 {get;set;}
    public override int GetHashCode()
    {
        int hashCode = 0;
        hashCode = hashCode         
            ^ a_2_id.GetHashCode() 
            ^ b_field1.GetHashCode();
        return hashCode;
    }
    public override bool Equals(object obj)
    {
        var toCompare = obj as ClassB;
        return (toCompare != null) && (this.GetHashCode() != toCompare.GetHashCode());
    }
}
public class ClassBMap : ClassMap<ClassB>
{
    public ClassBMap()
    {
        Schema("dbo");
        Table("ClassB");
        Not.LazyLoad();
        CompositeId()           
            .KeyProperty(x => x.a_2_id, "a_2_id")
            .KeyProperty(x => x.b_field1, "b_field1");      
    }
}

public class ClassA
{
    public virtual int Id1 {get;set;}
    public virtual string Id2 {get;set;}
    public virtual IList<string> Bs { get; private set; }
    public override int GetHashCode()
    {
        return (Id1 << 16) ^ Id2.GetHashCode();
    }
    public override bool Equals(object obj)
    {
        var toCompare = obj as ClassA;
        return (toCompare != null) && (this.Id1 == toCompare.Id1) && (this.Id2 == toCompare.Id2);
    }
}
public class ClassAMap : ClassMap<ClassA>
{
    public ClassAMap()
    {
        Schema("dbo");
        Table("ClassA");
        Not.LazyLoad();
        CompositeId()           
            .KeyProperty(x => x.Id1, "a_1_id")
            .KeyProperty(x => x.Id2, "a_2_id");
        HasMany(x => x.ClassBs)
            .AsSet()
            .Table("ClassB")
            .KeyColumn("a_2_id")
            .Not.LazyLoad(),
            .Element("b_field1");  // if there is only 1 value column or
            .Component(c =>        // if there is more than 1 value column
            {
                c.ParentReference(x => x.A);
                c.Map(x => x.Value1, "b_field1");
                c.Map(x => x.Value2, "b_field2");
                c.Map(x => x.Value3, "b_field3");
            });
    }
}
public class ClassB
{
    public virtual ClassA A {get;set;}
    public virtual string Value1 {get;set;}
    public virtual string Value2 {get;set;}
    public virtual string Value3 {get;set;}
}