I have a problem with entityframewrok wich serializes a 1:0..1 relation between two tables as a collection.
I have 2 tables on my Database:
CREATE TABLE `revisiones` (
`Id` int(11) NOT NULL AUTO_INCREMENT,
---Irrelevant columns here---
PRIMARY KEY (`Id`),
---Irrelevant constraint and foreign keys here---
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
CREATE TABLE `ficha_deposito` (
`Id` int(11) NOT NULL AUTO_INCREMENT,
`IdRevision` int(11) NOT NULL,
---Irrelevant Columns Here---
PRIMARY KEY (`Id`),
UNIQUE KEY `IdRevision_UNIQUE` (`IdRevision`),
CONSTRAINT `fk_ficdep_rev` FOREIGN KEY (`IdRevision`) REFERENCES `revisiones` (`Id`) ON DELETE CASCADE ON UPDATE CASCADE,
---Irrelevant constraints here---
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
As you can see a revision may be related as none or 1 ficha_deposito, due the unique restriction.
However on the edmx file, the relation is serialized as a collection:
If i try to change it manually (I would prefer to not do so, because if i have to regenerate the model, i will have to set the value again manually), then i get an exception:
Running transformation: Multiplicity is not valid in Role 'ficha_deposito' in relationship 'fk_ficdep_rev'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be *.
Why can't I change the multiplicity of the relation? revision.ficha_deposito should be null or a simple object.
This is a EF6 limitation. EF naturally supports one-to-one relationship via so called Shared Primary Key Associations, where there is no separate FK in the dependent entity, but the PK is also used as FK to the principal table.
When the dependent entity is using a separate FK field, even if it's backed with an unique constraint, from EF perspective it's still one-to-many relationship. I can't explain it better than in the One-to-One Foreign Key Associations:
As you may have noticed, both associations in the fluent API code has been configured as a many-to-one — not one-to-one, as you might have expected. The reason is simple: Code First (and EF in general) does not natively support one-to-one foreign key associations. In fact, EF does not support any association scenario that involves unique constraints at all.
and then
The second limitation that this lack of support impose to us is more important: one to one foreign key associations cannot be bidirectional (e.g. we cannot define a property for the User on the Address class).
The good news are that such support has been added to EF Core, so when it becomes usable (v1.1 or later) you'll be able to set up such relationship. Until then, you should live with one-to-many.
Related
On setting DbContext, we have
modelBuilder.Entity<Person>(app =>
{
app.ToTable("Person");
});
The EFCore throws an exception:
The entity type "Person" requires a primary key to be defined
But our Person table doesn't have any primary key column.
How to avoid this ?
EF Core doesn't support tables without primary keys (aka heaps). The reason is simple: it needs to be able to manipulate individual records, something that cannot be safely achieved without a primary key.
As a resolution, you can add a dummy column/primary key of type int/identity or guid/uniqueidentifier, and just ignore it.
If I have an entity in EF and I also have foreign key property in that entity. Now I want to update related record. If I use both Foreign Key Association and Independent Association, Then which will be preferred by Entity Framework and why ?
Case : Suppose If I assign different entity to navigation property and different enityId in foreign key property. Then what will be saved in database ?
I think the foreign key in your case. Independent key just for the table's itself
Scenario:
Database first.
I have a table with no primary key set and I'm trying to make an update with Entity Framework.
This is the error message I keep getting:
The property 'inactive_date' is part of the object's key information and cannot be modified.
If I set the fields 'Entity Key' value to 'false' I get this error messge:
Modifications to tables where a primary key column has property 'StoreGeneratedPattern' set to 'Computed' are not supported. Use 'Identity' pattern instead. Key column: 'timestamp'. Table: 'plat12Model.Store.glchart'.
Would this be corrected if I created a primary key? Can I set a primary key in my code rather than on the database?
By default, EF will make tables without primary keys and views into read-only classes where every field is part of the composite key. You can modify the conceptual model to reflect the actual behavior as long as you retain a key value that EF will use for object tracking. As the error message states, you also need to make the columns no longer computed in order to update them as well.
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Closed 10 years ago.
Possible Duplicate:
1:1 relationship problems with EF Model First
Is there a way to define 1:1 relationships on a Entity Framework .edmx without get this annoying:
Error 1 Running transformation: Multiplicity is not valid in Role
'PESSOACPF' in relationship 'FK_CPF_PES'. Because the Dependent
Role properties are not the key properties, the upper bound of the
multiplicity of the Dependent Role must be
*.
Already defined the FK as PK on my table, removed the pk, tried to re-create the project over 10 times and doesn't help AT ALL.
Your Foreign Key must be defined as UNIQUE.
To enforce a 1:0 or 1:1 relationship.
You can create Table in SQL DB like this (Lets take Order and OrderDetails Tables)):
CREATE TABLE OrderDetails (
DetailsId INTEGER IDENTITY NOT NULL,
orderId INTEGER NOT NULL UNIQUE,
PRIMARY KEY (DetailsId),
FOREIGN KEY (orderId) REFERENCES Order(orderId)
)
For more details Implementing one-to-zero-or-one relation in SQL Server
I hope this will help to you.
Suppose I have a table structure such as:
Order
ID int, primary key
Name, string
OtherOrderFields...
RetailOrder
ID int, primary key
OrderID, foreign key
RetailOrderFields...
In entity framework 4, is it possible to set up table per type inheritance so that RetailOrder derives from Order? All the examples I've seen so far have the derived class using the foreign key (OrderID in this example) as the primary key for the table, but what if that's not the case and each table maintains its own primary key?
No, it's impossible. I think, your database schema guess aggregation (1-1 relation) instead of inheritance.