FluentNhibernate many-to-many and Inverse() - nhibernate

I have the following database tables defined:
Club: Id, Name
Member: Id, Name
ClubMember: ClubId, MemberId
I have the following entity Classes defined:
public class Club() {
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual IList<Member> Members { get; set; }
}
public class Member() {
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual IList<Club> Clubs { get; set; }
}
I have the following overrides defined:
public class MemberOverride : IAutoMappingOverride<Member>
{
public void Override(AutoMapping<Member> mapping_)
{
mapping_
.HasManyToMany(x_ => x_.Clubs)
.ParentKeyColumn("MemberId")
.ChildKeyColumn("ClubId")
.Cascade.All()
.Table("ClubMembers");
}
}
public class ClubOverride : IAutoMappingOverride<Club>
{
public void Override(AutoMapping<Club> mapping_)
{
mapping_
.HasManyToMany(x_ => x_.Members)
.ParentKeyColumn("ClubId")
.ChildKeyColumn("MemberId")
.Inverse()
.Table("ClubMembers");
}
}
I can see from my overrides that the Inverse on the ClubOverride means you cannot do the following
session.Save(club.Members.Add(member));
but this works:
session.Save(member.Clubs.Add(club);
But it doesn't make logical sense. I want to be able to save either the club with members or member with clubs.
Am I trying to do something impossible with FluentNhibernate?
TIA

Yes, you're right, that's not possible. But it's not a question of FluentNhibernate, NHibernate works like that.
Only one side is the owner of the relation and on charge of adding elements.
From official documentation:
Changes made only to the inverse end of the association are not persisted. This means that NHibernate has two representations in memory for every bidirectional association, one link from A to B and another link from B to A. This is easier to understand if you think about the .NET object model and how we create a many-to-many relationship in C#:

You can create add or remove methods on your entities that will help accomplish this:
public class Club() {
public virtual int Id { get; set; }
public virtual string Name { get; set; }
private IList<Member> members;
public virtual IEnumerable<Member> Members { get { return members.Select(x => x); } }
public Club() {
members = new List<Member>();
}
public virtual void AddMember(Member member){
if (members.Contains(member))
return;
members.Add(user);
member.AddClub(this);
}
public virtual void RemoveMember(Member member){
if (!members.Contains(member))
return;
members.Remove(member);
member.RemoveClub(this);
}
}

Related

HasKey: error while using Fluent API to configure which property should be used as the foreign key

I have two classes (Parent, Child) in ASP.Net Core and I'm using code first approach, my real project is more complex than that, so i have to use this method to migrate to database.
The issue here is when I'm defining the relations in Db Context class i face this error noting that I'm following this Microsoft document https://learn.microsoft.com/en-us/ef/core/modeling/relationships, and you can find the main class below:
Error: Cannot implicitly convert type 'System.Collections.Generic.List<logintest.Models.Chlid>' to 'System.Collections.Generic.IEnumerable<logintest.Models.Child>'. An explicit conversion exists (are you missing a cast?)
public class Parent
{
public int Id { get; set; }
public List<Chlid> Childs { get; set; }
}
public class Child
{
public int Id { get; set; }
public int ParentId { get; set; }
public Parent Parent { get; set; }
}
public class AppDbContext : DbContext
{
public DbSet<Parent> Parents { get; set; }
public DbSet<Child> Childs { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Child>()
.HasOne(p => p.Parent)
.WithMany(b => b.Childs)
.HasForeignKey(b => b.ParentId);
}
}

Entity framework code first, delete childs by updating parent

As entity framework states, "Code first", here we go with the code first...
public class BaseModel
{
[Key]
public Guid Id { get; set; }
public DateTime DateCreated { get; set; }
public DateTime DateChanged { get; set; }
public BaseModel()
{
this.Id = Guid.NewGuid();
this.DateCreated = DateTime.Now;
this.DateChanged = DateTime.Now;
}
}
public class Association: BaseModel
{
public string Name { get; set; }
public string Type { get; set; }
public virtual List<Rule> Rules { get; set; }
public Association()
: base()
{
}
}
public class Rule: BaseModel
{
[ForeignKey("Association")]
public Guid AssociationId { get; set; }
//[Required]
public virtual Association Association { get; set; }
//[Required]
public string Name { get; set; }
public string Expression { get; set; }
public virtual List<Action> Actions { get; set; }
public Rule()
: base()
{
}
}
public class Action: BaseModel
{
public string Name { get; set; }
public string ActionType { get; set; }
[ForeignKey("Rule")]
public Guid RuleId { get; set; }
public virtual Rule Rule { get; set; }
public int Order { get; set; }
public Action()
: base()
{
}
}
So these are my four model classes that are using entity framework code first.
Each inherit from the baseclass, so they all have an Id Guid as Primary Key.
An Association has a list of rules. (Rule has FK to Association)
A Rule as has a list of actions. (Action has FK to Rule)
What I would like to do is only change and save the most upwards class = Association.
For example when deleting a rule, I would like this code to work:
public ActionResult DeleteRule(Guid assId, Guid ruleId)
{
Association ass = this.DataContext.Associations.FirstOrDefault(a => a.Id == assId);
ass.Rules.RemoveAll(r => r.Id == ruleId);
this.DataContext.SaveChanges();
return RedirectToAction("Index");
}
On the context.savechanges this is giving me this error:
'The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.'
This error also occurs when deleting an action.
Is there a way to change the most upper (Association) object AND ONLY changing things to this Association.
I DO NOT want to say context.Rules.remove(...) or context.actions.remove(...)
here's the source: http://server.thomasgielissen.be/files/mvctesting.zip
you need VS2012, all nuget packages are included in zip and you should be able to build and run the project.
Thanks in advance for your feedback!
Greetz,
Thomas
I you want to fix this issue, you should store your relations through junction tables. I don't think that you can achieve what you need, with this model.
However if you put a junction table(or entity) between your entities, you can easily remove child objects and update parent object.
For example, put a junction entity between Association and Rule:
public class AssociationRule: BaseModel
{
public Guid AssociationId { get; set; }
public Guid RuleId { get; set; }
[ForeignKey("AssociationId")]
public virtual Association Association { get; set; }
[ForeignKey("RuleId")]
public virtual Rule Rule { get; set; }
public Association()
: base()
{
}
}
Now, you can easily remove any rule from any association:
public ActionResult DeleteRule(Guid assId, Guid ruleId)
{
AssociationRule assr = this.DataContext
.AssociationRuless
.FirstOrDefault(ar => ar.AssociationId == assId && ar.RuleId == ruleId);
this.DataContext.AssociationRules.Remove(assr);
this.DataContext.SaveChanges();
return RedirectToAction("Index");
}

Doesn't update many to many attribute using NHibernate

Suppose I have only two classes: Group and User. User has groups and Group has members (instance of users)
public class User {
public virtual int id { set; get; }
public virtual string username { set; get; }
public virtual IList<Group> groups { set; get; }
public User()
{
groups = new List<Group>();
}
public virtual void joinGroup(Group group)
{
if (this.groups.Contains(group))
throw new AlreadyJoinedException();
group.members.Add(this);
this.groups.Add(group);
}
public class Group
{
public virtual int id { set; get; }
public virtual string name { set; get; }
public virtual User administrator { set; get; }
public virtual IList<User> members { set; get; }
public Group()
{
members = new List<User>();
}
As you can see the domain it's quite simple. I've already mapped both classes correctly using Fluent NHibernate,
public class UserMapping : ClassMap<User>
{
public UserMapping()
{
this.Id(user => user.id).GeneratedBy.Identity();
this.Map(user => user.username).Not.Nullable().Length(50).Not.LazyLoad();
this.HasManyToMany(user => user.groups).Table("MemberPerGroup").ParentKeyColumn("id_user").ChildKeyColumn("id_group").Not.LazyLoad();
}
}
public class GroupMapping : ClassMap<Group>
{
public GroupMapping()
{
this.Id(group => group.id).GeneratedBy.Identity();
this.Map(group => group.name).Not.Nullable().Length(50).Not.LazyLoad();
this.References(group => group.administrator).Not.Nullable().Not.LazyLoad();
this.HasManyToMany(group => group.members).Table("MemberPerGroup").ParentKeyColumn("id_group").ChildKeyColumn("id_user").Not.LazyLoad();
}
}
I'm progamming a web application using ASP MVC 4. My problem shows up when a user tries to join group. It doesn't break but it neither works fine (doesn't insert into the table the new row in MemberPerGroup). I'm doing something like it:
public void JoinGroup(User user,Group group){
this.userRepository.GetSessionFactory().TransactionalInterceptor(() =>
{
user.joinGroup(group);
});
}
Thanks in advance.
Ivan.
It seems your mapping has no cascading set?
this.HasManyToMany(group => group.members)
.Table("MemberPerGroup")
.ParentKeyColumn("id_group")
.ChildKeyColumn("id_user")
.Not.LazyLoad()
.Cascade.SaveUpdate();
I'm curious - why do you use GetSessionFactory()? our repositories take an ISession object in the constructor, (injected by autofac, but that's irrelevant) from which we start our queries:
// even better to use a transaction, but this is just a sample
_session.SaveOrUpdate(user);
_session.Flush();

Entity Framework Code First Many-to-Many relationship and inheritance

Forgive me if this question has been answered somewhere, I have been having a hard time finding a solution for this problem.
I am trying to set up EF Code First on an MVC4 Project. I have a User and Customer that both inherit from Person. I then have a Template object that has a Many-to-Many relationship with Customer and a One-to-Many relationship with User. Here is how I have it set up:
MODELS
public class Person
{
[Key]
public int PersonID { get; set; }
public string LastName { get; set; }
public string FirstName { get; set; }
public string FullName
{
get
{
return String.Format("{0} {1}", FirstName, LastName);
}
}
public string Email { get; set; }
public virtual List<Template> Templates { get; set; }
}
public class User : Person
{
....
}
public class Customer : Person
{
....
}
public class Template
{
public int TemplateId { get; set; }
public string TemplateName { get; set; }
public virtual List<Customer> Customers { get; set; }
[ForeignKey("User")]
public int UserId { get; set; }
public virtual User User { get; set; }
}
CONTEXT
public class ProjectContext : DbContext
{
public ProjectContext()
: base("name=ProjectDB")
{
}
public DbSet<Template> Templates { get; set; }
public DbSet<User> Users { get; set; }
public DbSet<Customer> Customers { get; set; }
public DbSet<Person> People { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions
.Remove<PluralizingTableNameConvention>();
modelBuilder.Entity<Template>()
.HasMany(x => x.Customers)
.WithMany(x => x.Templates)
.Map(x => x.MapLeftKey("TemplateId")
.MapRightKey("PersonId")
.ToTable("TemplateCustomer")
);
}
}
If I remove the Person DBSet out of the context this works fine but sets up TPT inheritance. I would like to use TPH inheritance, but when I enable migrations with the Person DBSet in the context it chokes:
NavigationProperty 'Templates' is not valid. Type 'MvcProject.Models.Customer' of FromRole 'Template_Customers_Target' in AssociationType 'MvcProject.Models.Template_Customers' must exactly match with the type 'MvcProject.Models.Person' on which this NavigationProperty is declared on.
Where am I going wrong here?
You cannot inherit navigation properties from a base entity. They always must be declared in the class the other end of the relationship is refering to.
Template.Customers is refering to Customer (not to Person), hence the inverse navigation property Templates must be declared in Customer (not in Person)
Template.User is refering to User (not to Person), hence the inverse navigation property Templates must be declared in User (not in Person)
So, basically you must move the Templates collection from Person into both derived classes:
public class Person
{
// no Templates collection here
}
public class User : Person
{
//...
public virtual List<Template> Templates { get; set; }
}
public class Customer : Person
{
//...
public virtual List<Template> Templates { get; set; }
}
Then you can define the two relationships with Fluent API like so:
modelBuilder.Entity<Template>()
.HasMany(t => t.Customers)
.WithMany(c => c.Templates) // = Customer.Templates
.Map(x => x.MapLeftKey("TemplateId")
.MapRightKey("PersonId")
.ToTable("TemplateCustomer"));
modelBuilder.Entity<Template>()
.HasRequired(t => t.User)
.WithMany(u => u.Templates) // = User.Templates
.HasForeignKey(t => t.UserId);
Change your HasMany selector to People:
modelBuilder.Entity<Template>()
.HasMany(x => x.People) // here
.WithMany(x => x.Templates)
.Map(x => x.MapLeftKey("TemplateId")
.MapRightKey("PersonId")
.ToTable("TemplateCustomer")
);

Fluent hierarchy

I have the following situation with fluent nhibernate:
public class Stuff
{
public Stuff()
{
Entities = new List<Entity>();
}
public virtual int Id { get; set; }
public virtual IList<Entity> Entities { get; set; }
}
public abstract class Entity
{
public virtual int Id { get; set; }
public virtual string Type { get; set; }
public virtual Stuff Stuff { get; set; }
}
public class Person : Entity
{
public virtual string FirstName { get; set; }
public virtual string LastName { get; set; }
}
public class Animal : Entity
{
public virtual string Species { get; set; }
}
And then, i have the following code to use automap and generate these mappings:
var sessionFactory =
Fluently.Configure().Database(persistenceConfigurer).Mappings(
m =>
m.AutoMappings.Add(
AutoMap.Source(new Types(typeof(Entity), typeof(Person), typeof(Animal), typeof(Stuff))))
.ExportTo(#"e:\")).ExposeConfiguration(BuildSchema).BuildSessionFactory();
however, what's happening is that i get the following exception:
---> NHibernate.MappingException: Association references unmapped class: ConsoleApplication1.Models.Entity
if i make the entity class non abstract this works, however, i'd like to avoid having that table in the database but still maintain the hierarchy concept with the re
You need to add your auto mappings like this
AutoMap.AssemblyOf<Entity>(yourConfiguration).IgnoreBase<Entity>();
Not only will this ignore your Entity base class but you don't need to add each entity manually so long as each model inherits from Entity.