c# - NHibernate relationship has an issue with two-directional getting data -

i have 2 tables have many-to-many relation.

code of entities

public class product : baseentity {          public virtual string name { get; set; }     public virtual ilist<category> productcategory { get; set; }     public virtual float price { get; set; }     public virtual string description { get; set; }     public virtual datetime dateofadd { get; set; }     public virtual float discount { get; set; }     public virtual int salecount { get; set; }     public virtual byte[] image { get; set; } }  public class category : baseentity {     public virtual string name { get; set; }     public virtual string description { get; set; }     public virtual ilist<product> categoryproducts { get; set; }     public virtual void addproduct(product product)     {         this.categoryproducts.add(product);     }     public virtual void deleteproduct(product product)     {         this.categoryproducts.remove(product);     } } 

i map classes many-to-many in conform mapping.

  relationalmapper.manytomany<product, category>(); 

in xml mapping compiles this:

  <class name="product">     <id name="id" type="int32">       <generator class="identity" />     </id>     <property name="name" />     <list name="productcategory" table="productcategory">       <key column="product_key" />       <list-index />       <many-to-many class="category" column="category_key" />     </list>     <property name="price" />     <property name="description" />     <property name="dateofadd" />     <property name="discount" />     <property name="salecount" />     <property name="image" lazy="true" />   </class> <class name="category">     <id name="id" type="int32">       <generator class="identity" />     </id>     <property name="name" />     <property name="description" />     <list name="categoryproducts" table="productcategory" inverse="true">       <key column="category_key" />       <list-index />       <many-to-many class="product" column="product_key" />     </list>   </class> 

the issue can categories product entity, when try products category it's doesn't work , list empty.

i don't think can have list on both sides of many-to-many. 1 side can list - other side should bag or set. consider following data in productcategory table:

category_id product_id index =========== ========== ===== 1           3          0 1           4          1 2           3          0 2           4          1 

if access category.categoryproducts, well. category #1 has 2 products: first product #3 , second #4.

however, if try access product.productcategory, same index column cannot used list. our data says product #3 has 2 categories: #1 , #2 - both of them want first category in list, index = 0. product #4 has 2 categories, neither of them want first category in list because both have index = 1.

the index values in list should sequential starting zero. don't think it's possible 2 lists driven same table.