My question is, is there a possible Fluent NHibernate mapping for Parent and Child objects that does not require the Child object to have a Parent object property? I haven't figured out how to map the reference back to the Parent. When I call Create with the mappings as-is, I get an exception because the Child object does not have the required foreign key (required in the data store) back to the Parent.
I have two POCO classes:
public class Parent
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual IList<Child> Childs { get; set; }
}
public class Child
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual int ParentId { get; set; }
}
And some mappings:
public class ParentMap : ClassMap<Parent>
{
public ParentMap()
{
this.Table("Parents");
this.Id(x => x.Id);
this.Map(x => x.Name);
this.HasMany(x => x.Childs).KeyColumn("ChildId").Cascade.AllDeleteOrphan();
}
}
public class ChildMap : ClassMap<Child>
{
public ChildMap()
{
this.Table("Childs");
this.Id(x => x.Id);
this.Map(x => x.Name);
// Needs some sort of mapping back to the Parent for "Child.ParentId"
}
}
And Create method:
public Parent Create(Parent t)
{
using (this.session.BeginTransaction())
{
this.session.Save(t);
this.session.Transaction.Commit();
}
return t;
}
I want to be able to create a Parent object that has a list of Child objects, but not have the Child objects have references back to their Parent (other than the Parent ID). I want to do this to avoid the circular reference from Parent to a list of Childs back to the Parent object, since that is causing issues with JSON serialization.
You can map these entities without problem, try this:
public class ParentMap : ClassMap<Parent>
{
public ParentMap()
{
this.Table("Parents");
this.Id(x => x.Id);
this.Map(x => x.Name);
this.HasMany(x => x.Childs).KeyColumn("ChildId").Cascade.AllDeleteOrphan();
}
}
public class ChildMap : ClassMap<Child>
{
public ChildMap()
{
this.Table("Childs");
this.Id(x => x.Id);
this.Map(x => x.Name);
this.Map(x => x.ParentId);
// if you have a reference of Parent object, you could map as a reference, for sample:
this.References(x => x.Parent).Column("ParentId");
}
}
When you get entities from ISession, do not serialize it to some format because these can be proxies of nhibernate instead entities objects. Try to create DTO (Data Transfer Object) classes and convert these entities to a DTO object, and serialize it. You will avoid circular references. For sample:
public class ParentDTO
{
public int Id { get; set; }
public string Name { get; set; }
public int ParentId { get; set; }
/* here you just have the primitive types or other DTOs,
do not reference any Entity type*/
}
And when you need to read the values to share the serialized value:
var dto = ISession.Query<Parent>()
.Select(x =>
new ParentDTO() {
Id = x.Id,
Name = x.Name,
ParentId = x.ParentId)
.ToList();
Get this result from the Data Access Layer and try to serialize, for sample:
var result = Serialize(dto);
Related
I am trying to update an nHibernate object with a child collection using the .Update() method found on a hibernate session. The only thing that I can do with the current setup is add children, I can not modify them or remove them.
For clarification the objects and their mapping are as follows:
public class Parent {
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual ISet<Child> Children { get; set; } = new HashSet<Child>();
}
public class ParentMap: ClassMap<Parent>
{
public ParentMap()
{
Id(x => x.Id);
Map(x => x.Name);
HasMany(x => x.Children)
.AsSet()
.Inverse()
.Cascade.AllDeleteOrphan();
}
}
public class Child {
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual Parent Parent { get; set; }
}
public class ChildMap: ClassMap<Child>
{
public ChildMap()
{
Id(x => x.Id);
Map(x => x.Name);
References(x => x.Parent);
}
}
When I get changes from my UI layer and try to update the already existing object using:
using (var tx = _session.BeginTransaction())
_session.Update(newParent);
tx.Commit();
}
Here newParent is a transient object (obtained from the database in an earlier session andd shown in the UI) containing the same identifier as the object I would like to update, but with changes to the child collection. Somehow using this approach I can only add children, but not modify or remove them.
Where is my mistake?
Most likely what is happening to you, is that instead of modifying the set that NHibernate has instantiated in your Parent entity, you are replacing it all together by a new instance of HashSet.
When you save or get an entity from NHibernate, your Children ISet gets loaded with an instance of a PersistentGenericSet (that implements ISet) which has the responsibility of helping with this change tracking for your collection.
In short, do not assign to the Children property. In fact, make the setter protected.
Just Add() or Remove() or Clear() it as required.
Afternoon all. I'm trying to create a mapping for a flight segment database where at the bottom of the mapping tree a FlightSegment references an origin and destination table with a compositeID consisting of a three letter code and a Boolean determining whether the code is or isn't a city.
Below are the relevant simplified class structures:
public class GTIFlightSegment
{
public virtual int ID { get; protected set; }
public virtual GTIOriginAirport Origin { get; set; }
public virtual GTIDestinationAirport Destination { get; set; }
public virtual GTIFlightSegmentGroup Parent { get; set; }
}
public class GTIAirport
{
public virtual string Code { get; set; }
public virtual string Name { get; set; }
public virtual string City { get; set; }
public virtual string CountryCode { get; set; }
public virtual GTIGeoCode GeoCode {get; set; }
public virtual string Terminal { get; set; }
public virtual bool IsCity { get; set; }
public GTIAirport()
{
GeoCode = new GTIGeoCode();
IsCity = false;
}
public override bool Equals(object obj)
{
var other = obj as GTIAirport;
if (ReferenceEquals(null, other)) return false;
if (ReferenceEquals(this, other)) return true;
return this.Code == other.Code && this.IsCity == other.IsCity;
}
public override int GetHashCode()
{
unchecked
{
int hash = GetType().GetHashCode();
hash = (hash * 31) ^ Code.GetHashCode();
hash = (hash * 31) ^ IsCity.GetHashCode();
return hash;
}
}
}
public class GTIOriginAirport : GTIAirport
{
public virtual GTIFlightSegment Parent { get; set; }
public GTIOriginAirport() : base()
{
}
}
public class GTIDestinationAirport : GTIAirport
{
public virtual GTIFlightSegment Parent { get; set; }
public GTIDestinationAirport() : base()
{
}
}
And below are the mappings I've created so far for the objects:
public class GTIFlightSegmentMap : ClassMap<GTIFlightSegment>
{
public GTIFlightSegmentMap()
{
Id(x => x.ID);
References(x => x.Destination).Columns(new string[] { "DestinationCODE", "DestinationIsCity" }).Cascade.All();
References(x => x.Origin).Columns(new string[] { "OriginCODE", "OriginIsCity"}).Cascade.All();
References(x => x.Parent).Not.Nullable();
}
}
public class GTIAirportMap : ClassMap<GTIAirport>
{
public GTIAirportMap()
{
Table("GTIAirport");
ReadOnly();
CompositeId()
.KeyProperty(x => x.Code, "CODE")
.KeyProperty(x => x.IsCity, "isCity");
Map(x => x.Name).Column("Airport");
Map(x => x.City);
Map(x => x.CountryCode);
Component(x => x.GeoCode, m =>
{
m.Map(x => x.Latitude);
m.Map(x => x.Longitude);
});
}
}
public class GTIOriginAirportMap : SubclassMap<GTIOriginAirport>
{
public GTIOriginAirportMap()
{
KeyColumn("CODE");
KeyColumn("isCity");
HasOne(x => x.Parent).PropertyRef(x => x.Origin);
}
}
public class GTIDestinationAirportMap : SubclassMap<GTIDestinationAirport>
{
public GTIDestinationAirportMap()
{
KeyColumn("CODE");
KeyColumn("isCity");
HasOne(x => x.Parent).PropertyRef(x => x.Origin);
}
}
What I'm trying to achieve is that when a FlightSegment is created in the system it will store the DestinationIsCity/DestinationCode and the OriginIsCity/OriginCode in the flight segments table but not try and update the GTIAirport reference table view. But when the objects are retrieved from the database with a query over, the rich information from the GTIAirport reference table will be fetched.
Or possibly have the Code and IsCity in the DepartureAirport and OriginAirport tables respectively with a ID reference back to the flight segment.
No matter what connotations I'm trying I'm hitting a wall of some kind. Basically I've got myself in a bit of a mess. I've flipped the relationships between the Airport and segment, swapping out to only references. Cascaded, not cascaded.
Common Errors being encountered whilst playing with the mappings:
1) The UPDATE statement conflicted with the FOREIGN KEY constraint
2) {"broken column mapping for: Destination.id of: GilesSabreConnection.Profiling.Model.BookingEngineModel.Model.GTIFlightSegment, type component[Code,IsCity] expects 2 columns, but 1 were mapped"}
3) {"Foreign key (FK582A9C81E6C3913B:GTIFlightSegment [Destination_id])) must have same number of columns as the referenced primary key (GTIDestinationAirport [CODE, isCity])"}
In case it's needed the fluent config is:
return Fluently.Configure().Database(MsSqlConfiguration.MsSql2012.ConnectionString(#"Data Source=Dev2;Initial Catalog=Sandbox;Integrated Security=True")).Mappings(m => m.FluentMappings.AddFromAssemblyOf<Profile>()).ExposeConfiguration(cfg => new SchemaUpdate(cfg).Execute(true, true)).BuildSessionFactory();
Any help to point me in the right direction from the database and fluent gurus would be greatly appreciated.
Many thanks in advance.
Realised that by setting the GTIAirport Map as readonly I was inherently making the Destination and Origin maps as readonly so the mapping could never work no matter how I was configuring the relationships.
So I've split the static reference database of detailed airport info accessed via the View named GTIAiport into two, so the Boolean in the composite key is no longer required. I now have the flight segment mapping simply logging the Airport origin/destination codes within the flight segment table using the Component class in fluent. In the Airport class itself now have a function to independently fetch the rich data from the static reference database table on request using the stored Airport code.
Couldn't figure out a way to do this with fluent. Interested to know if there is a way.
public GTIFlightSegmentMap()
{
Id(x => x.ID);
Component(x => x.Destination, m =>
{
m.Map(y => y.Code).Column("DestinationCode");
});
Component(x => x.Origin, m =>
{
m.Map(y => y.Code).Column("OriginCode");
});
;
References(x => x.Parent).Not.Nullable();
}
}
I am faced with an EF6 Code First context, with a few DbSets of POCOs that have navigation properties (and foreign keys) between them, e.g.:
public partial class Person
{
public Guid Id { get; set; }
public virtual ICollection<Address> Address { get; set; }
}
public partial class Address
{
public Guid Id { get; set; }
public Guid FK_PersonId { get; set; }
public virtual Person Person { get; set; }
}
modelBuilder.Entity<Person>()
.HasMany (e => e.Address)
.WithRequired (e => e.Person)
.HasForeignKey (e => e.FK_PersonId)
.WillCascadeOnDelete(false);
Given these types, is there any proper way (i.e. without resorting to iterating over the POCO properties/fields by reflection and "guessing") to programmatically determine that Address has an FK_PersonId pointing to the Id property of Person?
To get the FK property's names for an specific entity you can use this generic method:
public IEnumerable<string> GetFKPropertyNames<TEntity>() where TEntity:class
{
using (var context = new YourContext())
{
ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;
ObjectSet<TEntity> set = objectContext.CreateObjectSet<TEntity>();
var Fks = set.EntitySet.ElementType.NavigationProperties.SelectMany(n=>n.GetDependentProperties());
return Fks.Select(fk => fk.Name);
}
}
And if you want the nav. property's names the only you need to do is this:
//...
var navProperties = set.EntitySet.ElementType.NavigationProperties.Select(np=>np.Name);
Looks a common situation to me: I have two tables:
documents:
dID (pk, int), dName(varchar)
and document_options:
dID (int), oType(int), oValue(varchar)
I would like to have a class Document with a property Options (a List of DocumentOption class)
Since document_options has no PK I cannot use HasMany, and rows from this table don't seem like 'real' entities anyway...
I see a way to generate an auto-number key for document options and map with HasMany, or maybe create a composite ID, but I'd like to know if there is a better option that I don't know about.
In this case, DocumentOptions is a value object, since it has no identity of its own and has no meaning outside of the document it belongs to. So, you would use Component to map the collection properties to the value object.
public class Document : Entity // don't worry about Entity; it's a base type I created that contains the Id property
{
public virtual string Name { get; set; }
public virtual IList<DocumentOptions> Options { get; protected set; }
public Document()
{
Options = new List<DocumentOptions>();
}
}
public class DocumentOptions
{
public virtual int Type { get; set; }
public virtual string Value { get; set; }
}
And the mapping:
public DocumentMap()
{
Table("documents");
Id(c => c.Id)
.Column("dId")
.GeneratedBy.HiLo("10");
Map(c => c.Name)
.Column("dName");
HasMany(c => c.Options)
.Component(c =>
{
c.Map(c2 => c2.Value).Column("oValue");
c.Map(c2 => c2.Type).Column("oType");
})
.Table("document_options")
.KeyColumn("dId")
.Cascade.AllDeleteOrphan();
}
If I understand correctly I had to map options as a list of components:
HasMany(x => x.DocumentOptions)
.Table("document_options")
.KeyColumn("dID")
.Component(c => {
c.Map(x => x.Option, "oID");
c.Map(x => x.Value, "oValue");
})
.Fetch.Subselect(); //This type of join isn't strictly needed, is used for SQL optimization
classes FYI:
public class Options {
public virtual int Option { get; set; }
public virtual int Value { get; set; }
}
public class Document {
public virtual int ID { get; set; }
public virtual String Name { get; set; }
public virtual IList<DocumentOption> DocumentOptions { get; set; }
}
New to FluentNHibernate =D
I have a parent/children classes as follows:
public class Parent
{
public virtual int ID { get; private set; }
public virtual string Name { get; set; }
public virtual IList<Child> Children { get; set; }
}
public class Child
{
public virtual int ID { get; private set; }
public virtual string Name { get; set; }
public virtual Parent ActiveParent { get; set; }
}
With mappings of:
public ParentMap()
{
Id(x => x.ID);
Map(x => x.Name);
HasMany(x => x.Children)
.Inverse();
.Cascade.All();
}
public ChildMap()
{
Id(x => x.ID);
Map(x => x.Name);
//Map(x => x.ActiveParent)
// .Column(ParentID);
}
The commented out area of the child map is the question I'm currently having trouble with. I'd like to be able to create a child object and call its' parent(ie, someChild.ActiveParent), but am unsure on how to map this via the fluent interface.
The table structure for the child table holds a parentid, with the intent of lazy loading the parent object if called. Any help is always greatly appreciated.
References(x => x.Parent);
Adding to mxmissile's answer, you will want to add a LazyLoad() to the end of the References() call, and also you might want to do something like this in your configuration:
.Mappings(m =>
m.FluentMappings.AddFromAssemblyOf<ParentMap>()
.ConventionDiscovery.Add(ForeignKey.EndsWith("ID")))
The last line instructs Fluent NHibernate to expect foreign keys named like ParentID rather than the default (Parent_Id ?), so you no longer need to specify the column name explicitly in every relationship mapping.