Question: is there a way to map a single foreign key to a number of mutually exclusive tables, based on a context?
Background...
In my specific example, I have the following domain graph, representing an insurance claim which can be against a vehicle or property:
public enum InvolvedPartyContext
{
Vehicle = 1,
Property = 2
}
public class Claim
{
public virtual Guid Id { get; set; }
public virtual InvolvedPartyContext InvolvedPartyContext { get; set; }
public virtual Vehicle Vehicle { get; set; } // set if Context = Vehicle
public virtual Property Property { get; set; } // set if Context = Property
}
public class Vehicle { //... }
public class Property { //... }
The SQL looks like this (notice the single foreign key InvolvedPartyId):
CREATE TABLE Claims (
Id uniqueidentifier NOT NULL,
InvolvedPartyContext int NOT NULL,
InvolvedPartyId uniqueidentifier NOT NULL
)
CREATE TABLE Vehicles (
Id uniqueidentifier NOT NULL,
Registration varchar(20) NOT NULL
)
CREATE TABLE Properties (
Id uniqueidentifier NOT NULL,
PostCode varchar(20) NOT NULL
)
The Fluent NHibernate mapping file for Claim:
public ClaimMap()
{
Id(x => x.Id);
Map(x => x.InvolvedPartyContext).CustomTypeIs(typeof(InvolvedPartyContext));
References(x => x.Vehicle, "InvolvedPartyId");
References(x => x.Property, "InvolvedPartyId");
}
This throws an "Invalid index {n} for this SqlParameterCollection with Count {m}" exception, since the same field (InvolvedPartyId) is mapped twice. A simple fix would be to create VehicleId and PropertyId fields, but in the real world there are many more contexts, so this isn't very flexible.
Personally, I wouldn't go with the design you have. Instead I'd create subclasses of your Claim class, VehicleClaim and PropertyClaim respectively.
public class VehicleClaim : Claim
{
public virtual Vehicle Vehicle { get; set; }
}
Then change your mappings to use your InvolvedPartyContext column as a discriminator (the column which NHibernate uses to determine which class the row represents), and create subclass mappings for each subclass.
public class ClaimMap : ClassMap<Claim>
{
public ClaimMap()
{
Id(x => x.Id);
DiscriminateSubClassesOnColumn("InvolvedPartyContext");
}
}
public class VehicleClaimMap : SubclassMap<VehicleClaim>
{
public VehicleClaimMap()
{
DiscriminatorValue(1);
References(x => x.Vehicle);
}
}
If you really do want to run with what you've got, you should look into the any mappings; there isn't a lot of documentation on them, but you use the ReferencesAny method.
Related
I have small problem with nHibernate (fluent) I have two objects, one contains another - a parent and a child (predefined objects, readonly).
mappings:
public class ParentClass
{
public virtual int Id { get; set; }
public virtual ChildClass Metoda { get; set; }
}
public ParentClassMap() {
Table("Wyceny");
Id(x => x.Id).Column("Id").GeneratedBy.TriggerIdentity();
References(x => x.Metoda).Column("RMW_ID");
}
public ChildClass
{
public virtual int Id { get; set; }
public virtual string Nazwa { get; set; }
}
public ChildClassMap()
{
Table("Metody");
Id(x => x.Id).Column("Id");
Map(x => x.Nazwa).Column("Nazwa_met");
}
Everything works perfectly until I chose child object with id = 0, reading still works for id=0, but when I'm trying to save or update Parent with correct ChildObject(readed previously from db through nHibernate), nHibernate stores null instead of value.
Any suggestions?
nHibernate 3.3.1.4000
fluent 1.4.0.0
The issue here would be the unsaved-value. NHibernate must decide if operations with object will be insert or update. This decision comes from unsaved-value setting, which is by default for int set to 0.
Try to extend your mapping of a ChildClass:
public ChildClassMap()
{
Table("Metody");
Id(x => x.Id)
.Column("Id")
.UnsavedValue(-1);
...
See 5.1.4. id, cite:
unsaved-value (optional - defaults to a "sensible" value): An identifier property value that indicates that an instance is newly instantiated (unsaved), distinguishing it from transient instances that were saved or loaded in a previous session.
And here is nice Id mapping overview by Adam Bar (the second half of the article)
I would like to be able to add a collection of Notes to any of my main entities in my NHibernate application. I can see how you could do this with a seperate junction table per entity. However, I would like to be able to avoid this and only have one junction table - if this is possible.
Below is the code so far, however this will result in all Notes being loaded for every Entity and I only want to load the notes for that particular entity. What are the alternative approaches I need to take?
public class Entity
{
public virtual int Id { get; set; }
}
public class EntityType1 : Entity
{
public EntityType1()
{
Notes = new List<Note>();
}
public virtual string EntityTypeName { get; set; }
public virtual IList<Note> Notes {get;set;}
}
public class EntityType2 : Entity
{
public EntityType2()
{
Notes = new List<Note>();
}
public virtual string EntityType2Name { get; set; }
public virtual IList<Note> Notes { get; set; }
}
public class Note
{
public virtual int Id { get; set; }
public virtual IList<Entity> Entities { get; set; }
public virtual string NoteText { get; set; }
}
}
namespace FluentNHib.Mappings
{
public class EntityMap : ClassMap<Entity>
{
public EntityMap()
{
Id(m => m.Id);
}
}
public class EntityType1Map : ClassMap<EntityType1>
{
public EntityType1Map()
{
Id(m => m.Id);
Map(m => m.EntityTypeName1);
HasManyToMany(m => m.Notes).Table("EntityToNotes")
.ParentKeyColumn("EntityId")
.ChildKeyColumn("NoteId")
.LazyLoad()
.Cascade.SaveUpdate();
}
}
public class EntityType2Map : ClassMap<EntityType2>
{
public EntityType2Map()
{
Id(m => m.Id);
Map(m => m.EntityType2ame);
HasManyToMany(m => m.Notes).Table("EntityToNotes")
.ParentKeyColumn("EntityId")
.ChildKeyColumn("NoteId")
.LazyLoad()
.Cascade.SaveUpdate();
}
}
public class NoteMap : ClassMap<Note>
{
public NoteMap()
{
Id(m => m.Id);
Map(m => m.NoteText);
}
}
I am not sure what the real issue is:
...however this will result in all Notes being loaded for every Entity and I only want to load the notes for that particular entity...
Is the issue in lazy loading? or in fact that Entity1 and Entity2 can have same ID, therefore the references are mixed? (I expect that and this should be part of the answer below)
Anyhow, I would say that we can achieve what you need: map the Note with just one table EntityToNotes. And that is good.
But, in general, I would descourage you from using the many-to-many. It is just my own feeling, experience. Below are some links with more explanation:
Am I doing many to many incorrectly when using fluent nhibernate?
NHibernate how do you map a crossreference table to a bag?
Nhibernate: How to represent Many-To-Many relationships with One-to-Many relationships?
Draft of the SOLUTION:
So, firstly we have to extend the table "EntityToNotes" with two columns
EntityToNoteId column - we need a primary key for new pairing object
Discriminator column
The Discriminator column will be used for (almost like a standard inheritance)
inserting Discriminator value during creation
filtering te IList<Notes> per Entity
These could be the pairing Entity (with an abstract base gathering the common stuff)
public abstract class EntityToNote<TEntity>
{
public abstract string Discriminator { get; set; }
public virtual TEntity Entity {get;set;}
public virtual Note Note {get;set;}
}
// the pairing objects
public class EntityType1ToNote : EntityToNote<EntityType1>
{
string _discriminator = "EntityType1"; // here we set the discriminator
public virtual string Discriminator
{
get { return _discriminator; }
set { _discriminator = value; }
}
...
// Similar for other pairing objects
The Entities will now be referencing lists of pairing objects
public class EntityType1 : Entity
{
public virtual IList<EntityType1ToNote> Notes {get;set;}
...
public class EntityType2 : Entity
{
public virtual IList<EntityType2ToNote> Notes { get; set; }
...
Here is snippet of the mapping (all other Entities will have usual mapping, including ClassMaps for EntityType1ToNote, EntityType2ToNote...)
public class EntityType1Map : ClassMap<EntityType1>
{
public EntityType1Map()
{
Id(m => m.Id);
Map(m => m.EntityTypeName1);
HasMany(m => m.Notes)
// this "table" setting is redundant, it will come from EntityType1ToNote
//.Table("EntityToNotes")
.KeyColumn("EntityId")
// here is the trick, that only related rows will be selected
.Where("Discriminator = 'EntityType1'")
.Cascade.AllDeleteOrphan();
}
}
As I tried to explain in the links provided, we gained this way a lot. Mostly the ability to use more columns on the pairing table - e.g. Discriminator (later we can have more columns like SortBy...) and we are able to use powerful searching with subqueries - see Query on HasMany reference
Also, in fact, the pairing could be mapped via the real inheritance... But the main point here is: Instead of many-to-many we introduced the pairing object and gained a lot
I'm having trouble getting entity framework to flatten my domain entity classes with Value Objects (complex type) fields to one table.
Everything works if I tell my model builder to ignore my value objects/complex type, but that results in all the attributes of the value object being missed in my tables. As soon as I remove the ignore statement i get "A value shared across entities is created in more than one location". If I look in the resulting CE SQL file I see an additional table named after my Domain class appended with a 1 and containing only the Value Object parameters.
Some Code:
My domain Classes:
public User {
private User(){}
public long Id {get; private set;} // dont ask, inherited legacy database
public string UserId { get; private set; }
public string Domain { get; private set; }
public AuditIformation AuditDetails {get ; private set;}
//..domain logic etc
}
public AuditInformation : IValueObject {
public long CreatedByUserId { get; private set; }
public DateTime CreatedDate { get; private set; }
}
My repository project (going code first) has got this:
public partial class myContext : DbContext {
protected override void OnModelCreating(DbModelBuilder mb) {
mb.Conventions.Remove<PluralizingTableNameConvention>();
mb.ComplexType<Domain.Model.AuditInformation>();
mb.ComplexType<Domain.Model.AuditInformation>().Property(a => a.CreatedDate).HasColumnName("Created_On");
mb.ComplexType<Domain.Model.AuditInformation>().Property(a => a.CreatedByUserId).HasColumnName("Created_By");
//This line lets everything work but doesn't include my
//AuditInformation attributes in my User Table.
mb.Ignore<Domain.Model.AuditInformation>(); // <== I think I need to remove this
//..
mb.Entity<User>().Map(a => {
a.Property(x => x.Id).HasColumnName("Id");
a.Property(x => x.UserId).HasColumnName("User_Id");
a.Property(x => x.Domain).HasColumnName("User_Dmain");
})
.HasKey(x => x.Id)
.ToTable("Tbl_User"); //<==Again, dont ask
}
}
What I want to get is a table looking like:
[TBL_USER]
ID AS BIGINT,
USER_ID as VARCHAR(MAX),
USER_DMAIN AS VARCHAR(MAX),
CREATED_ON as DATE,
CREATED_BY as BIGINT
But what im getting is only:
[TBL_USER]
ID AS BIGINT,
USER_ID as VARCHAR(MAX),
USER_DMAIN AS VARCHAR(MAX),
and if I remove the ignore line i get this bonus freak table
[USER1] <<==Note, named after the domain class, not the destination table..
ID AS BIGINT,
CREATED_ON as DATE,
CREATED_BY as BIGINT
and a whole bunch of error when I try to use my repository:
----> System.Data.Entity.Infrastructure.DbUpdateException : A value shared across entities or associations is generated in more than one location. Check that mapping does not split an EntityKey to multiple store-generated columns.
----> System.Data.Entity.Core.UpdateException : A value shared across entities or associations is generated in more than one location. Check that mapping does not split an EntityKey to multiple store-generated columns.
----> System.ArgumentException : An item with the same key has already been added.
TearDown : System.NullReferenceException : Object reference not set to an instance of an object.
Ive done a lot of searching but I just cant find any concrete examples of persisting my value object attributes into the tables created for my domain objects. Can someone show me where I'm going wrong?
Try this:
public class AuditInformation
{
public long CreatedByUserId { get; set; }
public DateTime CreatedDate { get; set; }
}
public abstract class AuditInfo
{
public AuditInformation AuditDetails { get; set; }
public AuditInfo()
{
this.AuditDetails = new AuditInformation();
this.AuditDetails.CreatedByUserId = 0;
this.AuditDetails.CreatedDate = DateTime.Now;
}
}
public User : AuditInfo
{
private User(){}
public long Id {get; private set;} // dont ask, inherited legacy database
public string UserId { get; private set; }
public string Domain { get; private set; }
//..domain logic etc
}
public partial class myContext : DbContext
{
public DbSet<User> Users { get; set; }
protected override void OnModelCreating(DbModelBuilder mb)
{
mb.Conventions.Remove<PluralizingTableNameConvention>();
mb.ComplexType<Domain.Model.AuditInformation>();
mb.ComplexType<Domain.Model.AuditInformation>().Property(a => a.CreatedDate).HasColumnName("Created_On");
mb.ComplexType<Domain.Model.AuditInformation>().Property(a => a.CreatedByUserId).HasColumnName("Created_By");
mb.Entity<Cricketer>().Map(a =>
{
a.Property(x => x.Id).HasColumnName("Id");
a.Property(x => x.UserId).HasColumnName("User_Id");
a.Property(x => x.Domain).HasColumnName("User_Dmain");
a.Property(x => x.AuditDetails.CreatedByUserId).HasColumnName("CreatedByUserId");
a.Property(x => x.AuditDetails.CreatedDate).HasColumnName("CreatedDate");
})
.HasKey(x => x.ID)
.ToTable("Tbl_User"); //<==Again, dont ask
}
}
I have two tables in my database. One is called Users, and the other is called Widgets. The Widgets table represents 3 entities in my code model. One of the entities, Widget, is a parent class for the other two entities, WidgetTypeA and WidgetTypeB. Both WidgetTypeA and WidgetTypeB have navigation properties to the User entity, which is persisted to the Users table in the database. I'm having trouble getting Code First to use the same foreign key for both the WidgetTypeA and WidgetTypeB entities (UserId). Does anyone know how to do this? It seems like it should be a common problem with Table Per Hierarchy mapping.
My entity classes are as follows:
public class Widget
{
public int Id { get; set; }
public string Name { get; set; }
}
class WidgetMap : EntityTypeConfiguration<Widget>
{
public WidgetMap()
{
ToTable("Widgets");
HasKey(w => w.Id);
Property(w => w.Id)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
Property(w => w.Name)
.IsRequired()
.HasMaxLength(75)
.IsUnicode(true);
}
}
public class WidgetTypeA : Widget
{
public int UserId { get; set; }
public virtual User User { get; set; }
public string Color { get; set; }
public int DepthLevel { get; set; }
}
class WidgetTypeAMap : EntityTypeConfiguration<WidgetTypeA>
{
public WidgetTypeAMap()
{
Map(w => w.Requires("WidgetTypeId").HasValue(1));
HasRequired(w => w.User)
.WithMany(u => u.WidgetTypeAs)
.HasForeignKey(w => w.UserId)
.WillCascadeOnDelete(false);
Property(w => w.Color)
.IsOptional()
.IsUnicode(true)
.HasMaxLength(75);
Property(w => w.DepthLevel)
.IsOptional();
}
}
public class WidgetTypeB : Widget
{
public int UserId { get; set; }
public virtual User User { get; set; }
}
class WidgetTypeBMap : EntityTypeConfiguration<WidgetTypeB>
{
public WidgetTypeBMap()
{
Map(w => w.Requires("WidgetTypeId").HasValue(2));
HasRequired(w => w.User)
.WithMany(u => u.WidgetTypeBs)
.HasForeignKey(w => w.UserId)
.WillCascadeOnDelete(false);
}
}
public class User
{
public int Id { get; set; }
public string Username { get; set; }
public int Age { get; set; }
public virtual ICollection<WidgetTypeA> WidgetTypeAs { get; set; }
public virtual ICollection<WidgetTypeB> WidgetTypeBs { get; set; }
}
class UserMap : EntityTypeConfiguration<User>
{
public UserMap()
{
ToTable("Users");
HasKey(u => u.Id);
Property(u => u.Username)
.IsRequired()
.HasMaxLength(75)
.IsUnicode(true);
Property(u => u.Age)
.IsRequired();
}
}
At any rate, I keep getting the error
Invalid column name 'UserId1'
when I try to perform the following operations:
using (var entities = new MyEntities())
{
User u = new User
{
Username = "Frank",
Age = 14
};
entities.Users.Add(u);
entities.SaveChanges();
WidgetTypeA wa1 = new WidgetTypeA
{
Name = "0SDF81",
UserId = u.Id,
DepthLevel = 6
};
entities.WidgetTypeAs.Add(wa1);
entities.SaveChanges();
}
Not sure if this can be fixed or not. I can always specify a second UserId foreign key for the Widgets table, but that seems pointless. Perhaps there's a way to do this using Fluent API?
You cannot map properties defined in different derived entities to the same column. That is limitation in EF. If your WidgetTypeA has UserId property and your WidgetTypeB has UserId property they must be different columns in the database. It should work if you move both UserId and User properties from derived types to the parent Widget type.
I know its a long way late, but hopefully may help other readers.
Although Ladislav was correct that using a mapped Foreign Key is not supported in EF6, I did find a useful workaround.
It is possible to define a computed column specification whose expression simply refers to the original column. Userid in the description above. This can be used as the discriminator for the TPH mapping. With this approach, the column need not be persisted, but can be used for TPH, with the original column being available for use as a foreign key.
I'm trying to generate db schema using fluent nhibernate, nhibernate 3.0, spring.net 1.3.1 and SQLite. The create/update script generated by NHibernate is
create table LogEntries (Id UNIQUEIDENTIFIER not null, Hostname TEXT not null, LoggerName TEXT not null, LogLevel INTEGER not null, Message TEXT not null, primary key (Id))
create table Properties (Id INTEGER not null, Key TEXT, Value TEXT, LogEntry_id UNIQUEIDENTIFIER, Index INTEGER, primary key (Id))
But it fails with the following error
System.Data.SQLite.SQLiteException: SQLite error
near "Index": syntax error
The entities:
public class LogEntry
{
public virtual Guid Id { get; set; }
public virtual string LoggerName { get; set; }
public virtual string Message { get; set; }
public virtual int LogLevel { get; set; }
public virtual string Hostname { get; set; }
public virtual IList<Property> Properties { get; set; }
}
public class Property
{
public virtual int Id { get; set; }
public virtual string Key { get; set; }
public virtual string Value { get; set; }
}
And the mapping classes
public class LogEntryMap : ClassMap<LogEntry>
{
public LogEntryMap()
{
Table("LogEntries");
Id(x => x.Id).GeneratedBy.GuidComb();
Map(x => x.Hostname).Not.Nullable();
Map(x => x.LoggerName).Not.Nullable();
Map(x => x.LogLevel).Not.Nullable();
Map(x => x.Message).Not.Nullable();
HasMany(x => x.Properties).Cascade.AllDeleteOrphan().AsList();
}
}
public class PropertyMap : ClassMap<Property>
{
public PropertyMap()
{
Table("Properties");
Id(x => x.Id).GeneratedBy.Increment();
Map(x => x.Key);
Map(x => x.Value);
}
}
I'm currently learning NHibernate myself (reading NHibernate 3.0 Cookbook), so in no way am I an expert.
I have the same problem at the moment, having a HasMany-map Parent.Children in an SQLite environment. This also crashes on the Index syntax error.
From what I've managed to deduce, Index is a reserved keyword (isn't it in almost every RDBMS?). It seems these keywords are not escaped by default, and hence, the SQL-script is invalid.
According to the book, you can escape the columnnames by adding a backtick to the column-name:
HasMany(x => x.Children).Cascade.AllDeleteOrphan().AsList(p => p.Column("`Index"));
However, even though this "works", it generates the following SQL-query, which seems to have dropped the x:
create table Child (
Id INTEGER not null,
ChildType TEXT not null,
Version INTEGER not null,
Content TEXT,
Title TEXT not null,
Parent_id INTEGER,
"Inde" INTEGER,
primary key (Id)
)
So, either consider:
specifying a custom index columnname which isn't a keyword,
rely on the backtick auto-escape (no clue what's happening here, no time to check)
use a different collection type if you don't actually need an ordered list. See List vs Set vs Bag in NHibernate