Delete from <Map> - nhibernate

Question

I have mapping:
<class name="User" table="Users" lazy="false">
<id name="id" type="Int32" column="id">
<generator class="identity" />
</id>
<property name="name" column="name" type="String"/>
<map name="Urls" table="UserUrl" lazy="true" inverse="true" cascade="all">
<key column="user_id"></key>
<index column="url_type_id" type="Int32"/>
<one-to-many class="UserUrl"/>
</map>
</class>
<class name="UserUrl" table="UserUrl" lazy="false">
<id name="id" type="Int32" column="id">
<generator class="identity"/>
</id>
<property name="user_id" column="user_id" type="Int32" not-null="true"/>
<property name="UrlType" column="url_type_id" type="Int32" not-null="true"/>
<property name="Url" column="url" type="String" not-null="true"/>
</class>
Also I get
class User
{
IDictionary<int,UserUrl> Urls;
....
}
User currentUser = FindById(2);
currentUser.Urls.Remove(5);
So I remove one item from assosiation collection of Url. Then I call SaveOrUpdateCopy(...), But url from table UserUrl doesn't delete and there is no error.
Does anybody know how to delete child item from collection and from DB?

Answer 1

Set inverse to false for <map> element.

Answer 2

I try search in google but there is no information about difference between <map><one-to-many > and <map><composite-element> so I use <map><one-to-many >.
<map name="Urls" table="UserUrl" lazy="true" cascade="all-delete-orphans">
<key column="user_id"/>
<index column="url_type_id" type="Int32"/>
<composite-element>
<property name="UrlType" column="url_type_id" type="Int32" not-null="true"/>
<property name="Url" column="url" type="String" not-null="true"/>
</composite-element>
</map>
If the Url is not an independent entity, having an own Id, then you could map itas composite-element. The url is treated as a value type.There is no class UserUrl mapping anymore.
I use UserUrl class in other code

Answer 3

Try this:
<map name="Urls" lazy="true" cascade="all-delete-orphans">
You don't need table, because the table is defined in the class UserUrl mapping
You should not make it inverse, if it is not
You should cascade it all-delete-orphan to tell NH to remove items that are removed from the collection.
Not related to your questions, why do you have this in the url?
<property name="user_id" column="user_id" type="Int32" not-null="true"/>
You are mapping the foreign key there! I would never ever dare to do this.
Actually, I'm not sure if you should not actually map it like this:
<map name="Urls" table="UserUrl" lazy="true" cascade="all-delete-orphans">
<key column="user_id"/>
<index column="url_type_id" type="Int32"/>
<composite-element>
<property name="UrlType" column="url_type_id" type="Int32" not-null="true"/>
<property name="Url" column="url" type="String" not-null="true"/>
</composite-element>
</map>
If the Url is not an independent entity, having an own Id, then you could map it as composite-element. The url is treated as a value type. There is no class UserUrl mapping anymore.
Edit:
See the NH Reference Chapter 7, it explains the components.
If you get not-null problems on references, just remove the not-null
constraint on the foreign key. NH needs to insert some columns to get
primary keys if you use generator class="identity", so it stores
a null temporary.

Answer 4

-Btw, don't answer to your question if you are actually commenting to an
answer. You could be down-voted
-The problem is that I have no stackoverflow account, so only one way to login to site on the same name is to enter name and email under my post. I try to register account on that site with the same name and email, but when I log in it treats me as new user (not as I login fist time).
So I have no choice.
Also I find out that working code is
<map name="Urls" lazy="true" cascade="all-delete-orphans" inverse="true">
without inverse="true" it doesn't work.