I have a [User] table/class and a [Company] table/class and there is a link-table [UserCompany] between them.
When editing a User, beside basic information people also could change that user's access Companies, so I do the map like this in UserMap.cs:
HasManyToMany(u => u
.Companies)
.Cascade.SaveUpdate()
.Table("UserCompany")
.ParentKeyColumn("UserId")
.ChildKeyColumn("CompanyCode")
.Not.LazyLoad();
Also in CompanyMap.cs I set inverse like this:
HasManyToMany(c => c.Users)
.Inverse()
.Table("UserCompany")
.ParentKeyColumn("CompanyCode")
.ChildKeyColumn("UserId");
The problem now is: I could update [User] information/table, plus the linking data in [UserCompany] table. However, the Fluent Nhibernate also update the [Company] table which I don't need at all.
Is there any way I could let FN not update Company table?
To stop cascading updates just remove the
.Cascade.SaveUpdate()
from your Many-to-many mapping.
It could be a bit confusing. In comparison with the cascading used on <list>s and <map>s. In that case, the update is done directly on the child table (parent has more children... child contains the ParentId - cascade is reasonable to do operation on the child record)
But here we are working with a pair table. The relation is stored there. And this table will be always managed by NHibernate (implicit cascading).
The setting .Cascade.SaveUpdate() goes to other end of the many-to-many relation. To company table in our case. It could be handy.. but you can omit that and get everything running as expected.
Related
I am using fluent nHibernate for my mappings as follow:
public class ContentTagMap: ClassMap<Employee>
{
public EmployeeMap()
{
Id(t => t.Id);
Map(t => t.Name);
HasManyToMany(t => t.Company);
}
}
public class CompanyMap: ClassMap<Company>
{
public HelpMap()
{
Id(h => h.Id);
Map(h => h.CompanyName).Length(6000);
Map(h => h.address).Length(6000);
HasManyToMany(h => h.Employee);
}
}
These mappings produce Employee Table ,Company Table and EmployeeToCompany Table
Employee Table
Id Name
1 John
2 MAX
Company Table
Id CompanyName address
1 HTC ABC
2 HTC2 India
EmployeeToCompany Table
Employee_Id Company_Id
1 1
2 1
How can I delete the employee with Id 1?
Unless I'm misunderstanding your question you should be asking:
How can i delete the content of the table using NHibernate?
Fluent NHibernate is only a tool to aid in the mapping of your entities. NHibernate is what you use to create, read, update and delete data. In any event:
9.5. Deleting persistent objects
ISession.Delete() will remove an object's state from the database. Of
course, your application might still hold a reference to it. So it's
best to think of Delete() as making a persistent instance transient.
From the NHibernate Documentation
You probably want to also define a Cascading style on your many to many relationship (HasManyToMany) in your mapping.
If you use Cascade.SaveUpdate in your many to many whenever you delete an entity on one side of the relationship it will delete that entity and any relationships. If you remove the association (ex. if you removed an Employee from a Company) it will only delete the relationship (EmployeeToCompany). This is what I've typically found to work in the case of many to many relationships.
Look at this article for more details on mapping and using a many to many relationship in Fluent NHibernate.
how to keep many to many relationships in sync with nhibernate?
I'm working with a legacy database put together by some very strange people. I'm writing an NHibernate DAL over the top of it but running into some odd mapping scenarios.
In one example, I have a table with a number of fields including LE_RECNUM (integer primary key) and LE_CODE (string).
However, all relationships throughout the database join onto LE_CODE, not LE_RECNUM, for some unfathomable reason.
I need to specify that LE_RECNUM is the Id in my mapping file, because I need the primary key to be generated when I insert records. However, I want all associations to use LE_CODE instead of LE_RECNUM.
Can anyone suggest how I might do this?
References(x => x.SomeProperty).Column("LE_CODE").PropertyRef(x => x.SomePropertyInParent);
I've got a many-to-many association between Lists and ListItems: a List knows about its Items, but a ListItem doesn't know about the containing lists. The cascade is saveupdate.
So, whenever I'm trying to delete a ListItem entity, I'm getting an SQLException saying I'm breaking the referential integrity. NHibernate tries to delete my ListItem without deleting the corresponding row in the linking table. The question is, is it possible to instruct NHibernate to delete my ListItem without breaking the referential integrity?
In case I have to manually remove the item from all containing lists, how do I properly do that?
Thanks a lot for any advice.
ulu
You need to set the mapping on the child to inverse=true. From another thread:
When you call SaveOrUpdate NHibernate
first deletes all of the child
objects. Then, because neither
relationship is marked as inverse,
NHibernate also tries to set the
foreign key column in your child table
to null. Since the rows have already
been deleted, you receive the second
error. You need to set inverse=true on
one side of your relationship to fix
this. This is usually done on the one
(primary key or parent) side. If you
do not do this, NHibernate will make
the appropriate updates for each side
of the relationship.
public class StoreMap : ClassMap<Store>
{
public StoreMap()
{
Id(x => x.Id);
Map(x => x.Name);
HasMany(x => x.Staff)
.Inverse() // Magic code!
.Cascade.All();
}
}
I have a standard parent - child (1:many) relationalship, configured using Fluent NHibernate:
On the parent side:
HasMany(x => x.Items).Inverse().Cascade.All();
and on the child side:
Map(x => x.ItemCategory).Nullable().Index("idx_item_category").Not.LazyLoad()
(Edit in response to epitka's comment:)
The record is deleted by calling
session.Delete(item_category)
This is the only operation done in the transaction.
(End Edit)
Currently when I delete an ItemCategory record it cascade the delete to all the items, which appears to be working as expected according to the documentation.
What I want is for Item.ItemCategory to be set to null automatically when the ItemCategory record is deleted.
I can only seem to turn off the cascade completely, which leads to a broken database (item's referencing a missing category). So, currently I have to do this manually which is a little more error prone than I'd like.
Is it possible to configure this behaviour?
session.Delete(item_category)
Whil it's not possible to do that out of the box, you can probably implement an IPreDeleteEventListener that fires an HQL update to set the Items' ItemCategory to null.
I've got two objects a parent and a child list. In my fluent nhibernate mapping for the parent I want to load the list of the children.
However I want this to be conditional, a column in the child table is called "IsDeleted" and I only want to return the children where "IsDeleted" is false.
Is it possible to set up a mapping to do this? If not is it possible to do it in just standard nhibernate?
Thanks
Yes, you can use a Where constraint in Fluent NHibernate to map this. Somehting like:
HasMany(x => x.Children).Where("IsDeleted = 0");
The Where constraint should use SQL syntax not HQL. For tables that allow soft deletes it's probably easier to map a view that filters the deleted records out.