I have a simple 1:many aggregate relationship, lets say:
public class Parent
{
public string Name {get; set;}
public Child SelectedChild {get; set;}
public Child PublishedChild {get; set;}
public virtual ICollection<Child> AllChildren {get; set;}
}
public class Child
{
public string Name {get; set;}
[Required]
public Parent Father {get; set;}
}
When creating the schema from this model I get the error:
Introducing FOREIGN KEY constraint 'Parent_SelectedChild' on table 'Parent' may cause cycles or multiple cascade paths.
Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints
So I add the following to OnModelCreating:
modelBuilder.Entity<Child>()
.HasRequired(v => v.Parent)
.WithOptional(c => c.SelectedChild)
.WillCascadeOnDelete(false);
modelBuilder.Entity<Child>()
.HasRequired(v => v.Parent)
.WithOptional(c => c.PublishedChild)
.WillCascadeOnDelete(false);
This gets round the original error but I now get:
Unable to determine the principal end of the 'xxx.Parent_SelectedChild' relationship.
Multiple added entities may have the same primary key.
Can anyone help?
All I essentially want to do is refer to particular child records on a 1:many aggregate relationship from the parent. I assume EF will create INT child id columns on the parent called e.g. SelectedChild_Id & PublishedChild_Id (or similar).
Thanks in advance
-macon
Edit: In response to #Slauma:
I can get a schema generated using:
modelBuilder.Entity<Parent>()
.HasOptional(p => p.SelectedChild)
.WithOptionalPrincipal()
.WillCascadeOnDelete(false);
modelBuilder.Entity<Parent>()
.HasOptional(p => p.PublishedChild)
.WithOptionalPrincipal()
.WillCascadeOnDelete(false);
modelBuilder.Entity<Parent>()
.HasMany(p => p.AllChildren)
.WithRequired(c => c.Father)
.WillCascadeOnDelete(false);
But this generates multiple FK on the Child record e.g. Parent_Id, Parent_Id1. I just want a reference from the Parent to one of the child rows e.g. Parent_SelectedChildId. Do I have to do this manually with an int column on parent?
I think you have three 1-to-many relationships:
modelBuilder.Entity<Parent>()
.HasOptional(p => p.SelectedChild)
.WithMany()
.WillCascadeOnDelete(false);
modelBuilder.Entity<Parent>()
.HasOptional(p => p.PublishedChild)
.WithMany()
.WillCascadeOnDelete(false);
modelBuilder.Entity<Parent>()
.HasMany(p => p.AllChildren)
.WithRequired(c => c.Father)
.WillCascadeOnDelete(false);
Edit
I've tested my mapping above with exactly the Parent and Child class you provided in your question - with the only exception that I have added a primary key property to both classes: public int Id { get; set; }. Otherwise EF would complain about a missing key property. This mapping doesn't throw an exception and creates the following tables in the database:
Parents table:
- Id int not nullable (PK)
- Name nvarchar(MAX) nullable
- SelectedChild_Id int nullable (FK)
- PublishedChild_Id int nullable (FK)
Children table:
- Id int not nullable (PK)
- Name nvarchar(MAX) nullable
- Father_Id int not nullable (FK)
So, there are the three foreign key columns as expected.
Since you get an exception according to your comment, I guess that there is actually some important difference in the code you have tested.
BTW: Mapping the two navigation properties of the Parent class as One-to-One relationships is much more difficult, if not impossible. In EF you need a shared primary key between the two tables to map a One-to-One relationship, so it would not be possible to assign two different entities to the two navigation properties because they cannot both have the same key as the parent.
Related
I have two entities:
public class EntityA
{
public int? Id { get; set; }
public string Name { get; set; }
public EntityB { get; set; }
}
public class EntityB
{
public int? Id { get; set; }
public string Version { get; set; }
}
I have existing records for EntityB already in the database. I want to add a new EntityA with reference to one of the EntityB records.
var entityB = _dbContext.EntityB.FirstOrDefault(e => e.Id == 1);
var entityA = new EntityA { Name = "Test", EntityB = entityB };
_dbContext.Add(entityA);
_dbContext.SaveChanges();
When the above code runs I get the following error:
System.InvalidOperationException: The property 'Id' on entity type 'EntityB' is part of a key and so cannot be modified or marked as modified. To change the principal of an existing entity with an identifying foreign key first delete the dependent and invoke 'SaveChanges' then associate the dependent with the new principal.
This seems to me, that the save is trying to also add EntityB, not just a reference to it. I do have the relationship specified in the database as well as in Entity Framework, e.g. when querying for EntityA if I include EntityB in the select, I get the referenced entity as well (so the relationship works).
modelBuilder.Entity<EntityA>(e =>
{
e.HasKey(p => p.Id);
e.HasOne(p => p.EntityB)
.WithOne()
.HasForeignKey<EntityB>(p => p.Id);
}
modelBuilder.Entity<EntityB>(e =>
{
e.HasKey(p => p.Id);
}
How can I save a new EntityA, with only a reference to the selected EntityB, rather than saving both entities?
It looks like you are trying to Extend EntityB with an optional 1:1 reference to a Row n the new table EntityA. You want both records to have the same value for Id.
This 1:1 link is sometimes referred to as Table Splitting.
Logically in your application the record from EntityB and EntityA represent the same business domain object.
If you were simply trying to create a regular 1 : many relationship, then you should remove the HasOne().WithOne() as this creates a 1:1, you would also not try to make the FK back to the Id property.
The following advice only applies to configure 1:1 relationship
you might use Table Splitting for performance reasons (usually middle tier performance) or security reasons. But it also comes up when we need to extend a legacy schema with new metadata and there is code that we cannot control that would have broken if we just added the extra fields to the existing table.
Your setup for this is mostly correct, except that EntityA.Id cannot be nullable, as the primary key it must have a value.
public class EntityA
{
public int Id { get; set; }
public string Name { get; set; }
public EntityB { get; set; }
}
If you want records to exist in EntityA that DO NOT have a corresponding record in EntityB then you need to use another Id column as either the primary key for EntityA or the foreign key to EntityB
You then need to close the gap with the EntityA.Id field by disabling the auto generated behaviour so that it assumes the Id value from EntityB:
modelBuilder.Entity<EntityA>(e =>
{
e.HasKey(p => p.Id).ValueGeneratedNever();
e.HasOne(p => p.EntityB)
.WithOne()
.HasForeignKey<EntityB>(p => p.Id);
}
I would probably go one step further and add the Reciprocating or Inverse navigation property into EntityB this would allow us to use more fluent style assignment, instead of using _dbContext.Add() to add the record to the database:
public class EntityB
{
public int Id { get; set; }
public string Version { get; set; }
public virtual EntityA { get; set; }
}
With config:
modelBuilder.Entity<EntityA>(e =>
{
e.HasKey(p => p.Id).ValueGeneratedNever();
e.HasOne(p => p.EntityB)
.WithOne(p => p.EntityA)
.HasForeignKey<EntityB>(p => p.Id);
}
This allows you to add in a more fluent style:
var entityB = _dbContext.EntityB.FirstOrDefault(e => e.Id == 1);
entityB.EntityA = new EntityA { Name = "Test" };
_dbContext.SaveChanges();
This will trip up because you are using EntityA's PK as the FK to Entity B, which enforces a 1 to 1 direct relation. An example of this would be to have something like an Order and OrderDetails which contains additional details about a specific order. Both would use "OrderId" as their PK and OrderDetails uses it's PK to relate back to its Order.
If instead, EntityB is more like an OrderType reference, you wouldn't use a HasOne / WithOne relationship because that would require Order #1 to only be associated with OrderType #1. If you tried linking OrderType #2 to Order #1, EF would be trying to replace the PK on OrderType, which is illegal.
Typically the relationship between EntityA and EntityB would require an EntityBId column on the EntityA table to serve as the FK. This can be a property in the EntityA entity, or left as a Shadow Property (Recommended where EntityA will have an EntityB navigation property) Using the above example with Order and OrderType, an Order record would have an OrderId (PK) and an OrderTypeId (FK) to the type of order it is associated with.
The mapping for this would be: (Shadow Property)
modelBuilder.Entity<EntityA>(e =>
{
e.HasKey(p => p.Id);
e.HasOne(p => p.EntityB)
.WithMany()
.HasForeignKey("EntityBId");
}
An OrderType can be assigned to many Orders, but we don't have an Orders collection on OrderType. We use the .HasForeignKey("EntityBId") to set up the shadow property of "EntityBId" on our EntityA table. Alternatively, if we declare the EntityBId property on our EntityA:
modelBuilder.Entity<EntityA>(e =>
{
e.HasKey(p => p.Id);
e.HasOne(p => p.EntityB)
.WithMany()
.HasForeignKey(p => p.EntityBId);
}
On a side note, navigation properties should be declared virtual. Even if you don't want to rely on lazy loading (recommended) it helps ensure the EF proxies for change tracking will be fully supported, and lazy loading is generally a better condition to be in at runtime than throwing NullReferenceExceptions.
I am new to entity framework and am having a hard time trying to figure out how to query with a join when my models look like this (drastically simplified)
class Customer
{
public int Id {get; set;}
public Vehicles Vehicles {get; set;}
}
class Vehicles
{
public List<Vehicle> Items {get; set;}
}
class Vehicle
{
public int Id {get; set;}
public int CustomerId {get; set;}
}
If I put the List<Vehicle> on the customer class directly. I am able to do fluent mapping like this
builder.Entity<Customer>()
.HasMany(x => x.Items)
.WithOne()
.HasForeignKey(x => x.CustomerId);
Which then I can do this and I get back a customer object with vehicles
db.Customers.Include(x => x.Items).FirstOrDefault(x => x.Id == 1);
What I am not understanding is how to do this with my original set of models. I would like to keep them the way they are if possible. I have tried doing various versions of this in my onModelCreating method with no luck.
builder.Entity<Customer>(t =>
{
t.OwnsOne(x => x.Vehicles, v =>
{
v.HasMany(x => x.Items).WithOne().HasForeignKey(x => x.CustomerId);
});
});
It's possible to map the original classes, but in quite counterintuitive way.
Since the Vehicles class is just a container, mapping it as owned entity as you have tried seems the most natural way. However currently EF Core does not allow owned entity to be at the principal side of the relationship, and in your case this is needed.
So instead you need to map the Vehicles class as regular "entity" sharing the same table with the Customer - the so called table splitting. You have to do explcitly all that EF Core does implicitly for owned entities - define a shadow property and map is a both PK and FK for the one-to-one relationship with the Customer. You'd need also the explicitly map the Vehicle.CustomerId as a FK because from EF point of view the Vehicle is related to Vehicles rather than to Custome, hence the conventional FK property / column name assumed will be VehiclesId. Note that with this model you'll never be able to define an inverse navigation property Customer of the Vehicle.
With that being said, here is the fluent configuration needed:
modelBuilder.Entity<Vehicles>(builder =>
{
// Table
builder.ToTable(modelBuilder.Entity<Customer>().Metadata.Relational().TableName);
// PK
builder.Property<int>("Id");
builder.HasKey("Id");
// One-to-one relationship with Customer
builder.HasOne<Customer>()
.WithOne(e => e.Vehicles)
.HasForeignKey<Vehicles>("Id");
// One-to-many relationship with Vehicle
builder.HasMany(e => e.Items)
.WithOne()
.HasForeignKey(e => e.CustomerId);
});
and usage:
db.Customers
.Include(x => x.Vehicles.Items) // <--
// ...
Use .Join
See this question for some examples:
Entity Framework Join 3 Tables
I am coming from nHibernate and am trying to create an entity that has a 2 column composite key where both columns are also foreign keys.
For example I have a UserRole table that is (UserId Guid, RoleId Guid). I want to model this as
public class UserRole
{
public User User { get; set; }
public Role Role { get; set; }
}
EF doesn't seem to like this idea though. It seems to want me to also add Guid UserId {get;set;} and Guid RoleId { get; set; }. I managed to resolve this for the handling the FK part by defining the model in the dbcontext like so:
modelBuilder.Entity<UserRole>()
.HasRequired(x => x.Role)
.WithRequiredPrincipal()
.Map(x => x.MapKey("RoleId"));
modelBuilder.Entity<UserRole>()
.HasRequired(x => x.User)
.WithRequiredPrincipal()
.Map(x => x.MapKey("UserId"));
Which I hope I can turn into a convention. However when I tried to do this too:
modelBuilder.Entity<UserRole>().HasKey(x => new { x.User, x.Role });
it craps out at runtime with:
The property 'User' cannot be used as a key property on the entity 'Paroxysm.Domain.UserRole' because the property type is not a valid key type. Only scalar types, string and byte[] are supported key types.
FYI this is done in nHibernate byCode mapping like this (slightly different example):
public class ProjectUserProfileMap : ClassMap<ProjectUserProfile>
{
public ProjectUserProfileMap()
{
CompositeId()
.KeyReference(x => x.User, "UserId")
.KeyReference(x => x.Project, "ProjectId");
ReadOnly();
References(x => x.User, "UserId");
References(x => x.Project, "ProjectId");
Map(x => x.IsActive);
Map(x => x.ActivatedUtcDate).Not.Nullable().CustomType<NHibernate.Type.UtcDateTimeType>();
Map(x => x.InvitedUtcDate).Not.Nullable().CustomType<NHibernate.Type.UtcDateTimeType>();
Table("ProjectUserProfile");
}
}
So easy! Incidentally that little CustomType UTC behaviour doesn't seem to be supported by EF either.
Problem is not actually related to the fact that I have a composite key but having a single column PK which is also an FK would be a weird case (1:1 rel).
So I guess I want to know definitely if this can or cannot be done in EF6. The error message certainly indicates its not doable. Can someone confirm?
You could achieve this but only if you add to UserRole 2 foreign key properties: RoleId and UserId. This is because HasKey do not offer any mapping functionality - it can be defined only on properties existing in entity classes. It seems EF enforces that all Primary Key columns are always defined as concrete properties in classes wheres foreign key columns may not have corresponding properies defined. So to achieve what you want you need to define UserRole like this:
public class UserRole
{
public User User { get; set; }
public int UserId { get; set; }
public Role Role { get; set; }
public int RoleId { get; set; }
}
modelBuilder.Entity<UserRole>()
.HasRequired(x => x.Role)
.WithRequiredPrincipal()
.HasForeignKey(x => x.RoleId);
modelBuilder.Entity<UserRole>()
.HasRequired(x => x.User)
.WithRequiredPrincipal()
.HasForeignKey(x => x.UserId);
modelBuilder.Entity<UserRole>().HasKey(x => new { x.UserId, x.RoleId });
The exact situation as you posted you might alternatively achieve by many-to-many relationship:
modelBuilder.Entity<User>()
.HasMany(x => x.Roles)
.WithMany()
.Map(m =>
{
m.ToTable("UserRole");
m.MapLeftKey("UserId");
m.MapRightKey("RoleId");
});
With this you would achieve UserRole table with primary key defined on UserId and RoleId.
Table EMPLOYEE has MST_SQ (master-sequence) as both it's primary key, and as an FK to the primary key of table MASTER, which is also named MST_SQ. This table is used to join several other tables as well so that they all have the same PK. That is as far as my understanding goes.
I need to defined a 1 to 1 relationship in my model between class Employee and class Master, but I simply cannot find a way to do this. It seems only relationships with multiplicty allow an FK field to be speficied, and those that look like for 1 to 1, e.g. has optional(...)..WithRequiredPrincipal(....) has no FK space.
I could do some manual coding to link EMPLOYEE and MASTER when the are loaded, but how could I tell they were loaded. Is there any event that signals a POCO being populated from the DB? Or, the real question, how do I define this relationship in code?
From Relationships and Navigation Properties :
When working with 1-to-1 or 1-to-0..1 relationships, there is no
separate foreign key column, the primary key property acts as the
foreign key
From Configuring a Required-to-Optional Relationship (One-to–Zero-or-One) :
because the name of the property does not follow the convention the
HasKey method is used to configure the primary key
public class Master
{
public int MST_SQ { get; set; }
public virtual Employee Employee { get; set; }
}
public class Employee
{
public int MST_SQ { get; set; }
public virtual Master Master { get; set; }
}
The Employee has the MST_SQ property that is a primary key and a foreign key:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Master>().HasKey(m => m.MST_SQ);
modelBuilder.Entity<Employee>().HasKey(e => e.MST_SQ);
modelBuilder.Entity<Employee>()
.HasRequired(e => e.Master) //Employee is the Dependent and gets the FK
.WithOptional(m => m.Employee); //Master is the Principal
}
Generated migration code:
CreateTable(
"dbo.Employees",
c => new
{
MST_SQ = c.Int(nullable: false),
})
.PrimaryKey(t => t.MST_SQ)
.ForeignKey("dbo.Masters", t => t.MST_SQ)
.Index(t => t.MST_SQ);
CreateTable(
"dbo.Masters",
c => new
{
MST_SQ = c.Int(nullable: false, identity: true),
})
.PrimaryKey(t => t.MST_SQ);
So you don't need the "FK space" because EF makes it the foreign key without you having to specify it
I am a newbie in the EF. I read http://msdn.microsoft.com/en-us/data/gg193958.aspx and still confused.
I have an existing database and I'm writing a Code First model. I have Operators table with op_code Char(6) Primary Key. In the Operator class I named it OperatorCode, e.g.
[Key]
[Column("op_code",TypeName = "char")]
[DisplayName("Operator")]
public virtual string OperatorCode { get; set; }
In several of my tables I have EnteredBy and in some ModifiedBy columns that are FK to the op_code.
Say, for the Clients table I have both of these fields.
So, I added to the Operator class at the bottom:
[InverseProperty("EnteredBy")]
public virtual ICollection<Client> ClientsEnteredBy { get; set; }
[InverseProperty("ModifiedBy")]
public virtual ICollection<Client> ClientsUpdatedBy { get; set; }
and I added the following into the Client class:
public virtual Operator EnteredBy { get; set; }
public virtual Operator ModifiedBy { get; set; }
and I am getting a run-time error about EnteredBy_OperatorCode and ModifiedBy_OperatorCode columns.
What should I fix /add to let EF know my column names?
Thanks in advance.
Your foreign column names in the database do not match the default convention for FK names which is NavigationPropertyName_PrimaryKeyNameinTargetClass. Because your navigation properties are called EnteredBy and ModifiedBy and the primary key property is called OperatorCode EF expects - according to the mentioned convention - EnteredBy_OperatorCode and ModifiedBy_OperatorCode as foreign key columns. But those do not exist in the database which is the reason for your exception. Instead your FK columns are EnteredBy and ModifiedBy.
So, to fix the problem you must override the convention.
If you don't have FK properties in your model use Fluent API:
modelBuilder.Entity<Operator>()
.HasMany(o => o.ClientsEnteredBy)
.WithRequired(c => c.EnteredBy) // or HasOptional
.Map(m => m.MapKey("EnteredBy")); // mapping for the FK column name
modelBuilder.Entity<Operator>()
.HasMany(o => o.ClientsUpdatedBy)
.WithRequired(c => c.ModifiedBy) // or HasOptional
.Map(m => m.MapKey("ModifiedBy")); // mapping for the FK column name
(With this mapping you can remove the InverseProperty attribute.)
An alternative approach is to expose the FKs as properties in the model. Rename the navigation properties and use their names for the FK properties. The mapping is then possible with data annotations.
In Client class:
[ForeignKey("EnteredByOperator")]
public string EnteredBy { get; set; }
[InverseProperty("ClientsEnteredBy")]
public virtual Operator EnteredByOperator { get; set; }
[ForeignKey("ModifiedByOperator")]
public string ModifiedBy { get; set; }
[InverseProperty("ClientsUpdatedBy")]
public virtual Operator ModifiedByOperator { get; set; }
And remove the InverseProperty attributes in the Operator class.
Instead of the data annotations you can also use Fluent API:
modelBuilder.Entity<Operator>()
.HasMany(o => o.ClientsEnteredBy)
.WithRequired(c => c.EnteredByOperator) // or HasOptional
.HasForeignKey(c => c.EnteredBy);
modelBuilder.Entity<Operator>()
.HasMany(o => o.ClientsUpdatedBy)
.WithRequired(c => c.ModifiedByOperator) // or HasOptional
.HasForeignKey(c => c.ModifiedBy);
If both relationships are required you will need to disable cascading delete for at least one of the relationships (append .WillCascadeOnDelete(false) at the end of one of the mappings), otherwise SQL Server will throw an error that multiple cascading delete paths between the tables are not allowed.
I would suggest to use the "alternative approach" (expose foreign keys as properties) because it is easier to work with in most cases.