When performing a delete of a one-many relationship without exposing the foreign key, EF deletes the parent record and tries to null the foreign key on the child records. This of course causes an error because the foreign key is not nullable. Adding the foreign key to the child class overrides this behavior, but I'd rather not expose it.
For example given the following two classes, I'd prefer not to have JobId as a property of the Project class.
public class Job : ModelBase
{
[Required]
[StringLength(100)]
public string Company { get; set; }
[Required]
[StringLength(100)]
public string JobTitle { get; set; }
public ICollection<Project> Projects { get; set; }
}
public class Project : ModelBase
{
[Required]
[StringLength(100)]
public string Name { get; set; }
[Required]
public string Summary { get; set; }
public int JobId { get; set; }
}
Is there a way to enable cascading deletes in EF Code First without exposing the foreign key on the many side of the relationship?
Yup! Remove JobId and add the following:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Job>().HasMany(j => j.Projects).WithRequired();
}
In the database, this will add a cascading delete in the PK/FK relationship.
(I'm assuming that your ModelBase has an integer Id =)
Related
I'm trying add migration using EF core 2 code first method. The issue is that, the entities with foreign key relationship are created with a foreign key id suffixed with '1' at the end and a redundant column with the same name but without the 1 at the end which is not a foreign key.
Examples are my 2 classes, Store and StoreVisit as shown below:
Store
[Table("Store")]
public class Store
{
public Store()
{
StoreVisits = new HashSet<StoreVisit>();
}
[Key]
public int StoreId { get; set; }
[StringLength(30)]
public string ShopName { get; set; }
[StringLength(50)]
public string ShopKeeper { get; set; }
public string ContactNo { get; set; }
[StringLength(70)]
public string Address { get; set; }
[StringLength(20)]
public string Street { get; set; }
[StringLength(50)]
public string City { get; set; }
public IEnumerable<StoreVisit> StoreVisits { get; set; }
}
Store Visit
[Table("StoreVisit")]
public class StoreVisit
{
[Key]
public int StoreVisitId { get; set; }
[StringLength(50)]
public string Location { get; set; }
[StringLength(50)]
public string Notes { get; set; }
[DataType(DataType.Time)]
public DateTime StartTime { get; set; }
[DataType(DataType.Time)]
public DateTime EndTime { get; set; }
public Store Store { get; set; }
}
The Visit class is created in the database with the column shown in the image below:
As you can see, the StoreVisit table has columns "StoreId1" which is the actual foreign key and "StoreId" which is not a foreign key.
I have even configured the relationship with Fluent API as below:
modelBuilder.Entity<Store>()
.HasMany(c => c.StoreVisits)
.WithOne(e => e.Store)
.IsRequired();
Can someone help.
Note that Entity Framework Core is smart enough to detect relationships among your classes which will be turned into database tables with relationships if you use its conventions. So this is redundant to use annotations like [Key] above StoreId property.
Second thing, As an advice, try to use simple and clean names for classes or properties as they can be potentially similar to those automatically created by EF. For example, in your case I prefer to avoid using store inside StoreVisit class name again (e.g in case of many to many relationship, derived table is named StoreVisit like one that you employed just without 's', Although your case is one to many),
And Final tip is the reason for appearing redundant StoreId column. Actually, In your case, this is not necessary to use Fluent API as EF can detect the relationship. In addition, you've written wrong configuration for modelBuilder. So remove it and let EF to generate it (unless you plan to have fully defined relationship to consume its advantages in your code).
The StoreId is one that you told EF to generate it (as required)
in modelBuilder.
The StoreId1 is EF Auto generated column (Foreign Key) based on one
to many relationship. '1' is appended in order to avoid column name duplication.
A foreign key needs to be defined on the class.
[Table("StoreVisit")]
public class StoreVisit
{
[Key]
public int StoreVisitId { get; set; }
public int StoreId { get; set; }
[StringLength(50)]
public string Location { get; set; }
[StringLength(50)]
public string Notes { get; set; }
[DataType(DataType.Time)]
public DateTime StartTime { get; set; }
[DataType(DataType.Time)]
public DateTime EndTime { get; set; }
public Store Store { get; set; }
}
It also would hurt to add the foreign key reference to the Fluent API.
modelBuilder.Entity<Store>()
.HasMany(c => c.StoreVisits)
.WithOne(e => e.Store)
.HasForeignKey(e => e.StoreId)
.IsRequired();
"Introducing FOREIGN KEY constraint 'FK_dbo.AttendanceSheets_dbo.AdulLiteracyTeachers_ALTName' on table 'AttendanceSheets' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.\r\nCould not create constraint. See previous errors."}
public class AttendanceSheet
{
[Required]
[Key]
public int Attendanceid { get; set; }
[DisplayName("District")]
[ForeignKey("District")]
public int DistID { get; set; }
public virtual District District { get; set; }
[DisplayName("District")]
[ForeignKey("AdulLiteracyTeachers")]
public int ALTName { get; set; }
public virtual AdulLiteracyTeachers AdulLiteracyTeachers { get; set; }
[DisplayName("Month")]
public int Month { get; set; }
[DisplayName("Number Of Days")]
public int Attandence { get; set; }
}
Getting the above error while I am adding the controller using entity framework. Purpose is I want to pouplate whole Teacher list for attandance. I am using the foriegn key for teachers name
In your data context file add
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
}
below where you have your DbSets defined.
This happens when there are multiple paths to delete on entity from another through foreign keys.
For example
EntityA - EntityB - EntityC - EntityD
EntityA - EntityC - EntityD
EntityA - EntityD
There are multiple paths to delete the related EntityD, sql server doesn't allow this.
I have a property on my items class called vend_id which of course EF thinks is a foreign key to the vendor table. It actually should be a foreign key in the database but for reasons unknown to me the designers of the db chose not to make it a foreign key.
I am using EF to create a copy of the db schema on the local machine. When EF creates the database I want to tell it not to create a foreign key on the vend_id column. How do I do that? Ideally I do not want to rename the property because there are several such instances in my db and it just makes it confusing.
Thank you,
Sam
You can't have a navigation property to a Vendor entity in your Item entity class if the Items table does not have a foreign key to table Vendor. If you did not specify a navigation property in entity class Item, EF would not infer that vend_id is a foreign key.
Update:
Unable to reproduce with the following:
[Table("EntityA")]
public partial class EntityA
{
public int Id { get; set; }
public Nullable<int> EntityBId { get; set; }
public string Description { get; set; }
[ForeignKey( "EntityBId" )]
public virtual EntityB EntityB { get; set; }
// this is not created as a FK
// nor does EntityCId cause a FK
public int EntityC_Id { get; set; }
}
[Table("EntityC")]
public class EntityC
{
public EntityC()
{
EntitiesD = new HashSet<EntityD>();
}
public int EntityCId { get; set; }
public string Name { get; set; }
public virtual ICollection<EntityD> EntitiesD { get; set; }
}
I have one to one relationship with foreign keys but the Cascade Delete is not enabled for some reason. The sample code is below.
public class AppRegistration
{
public int AppRegistrationId { get; set; }
[Required]
[StringLength(50)]
[Display(Name = "Username")]
public string UserName { get; set; }
[Required]
[StringLength(100)]
public string Password { get; set; }
[StringLength(20)]
public string StudentOrAgent { get; set; }
// navigation properties
public virtual AppStatus AppStatus { get; set; }
public virtual Agreement Agreement { get; set; }
public virtual AnotherTable AnotherTable { get; set; }
}
The dependent table with a foreign key is below.
public class Agreement
{
[Key]
[ForeignKey("AppRegistration")]
public int AppRegistrationId { get; set; }
public DateTime DateAgreed { get; set; }
public virtual AppRegistration AppRegistration { get; set; }
}
When I try to delete an entry from the generated AppRegistrations table I get a Reference constraint conflict.
I tried putting [Required] on the navigation property in the dependent table but it doesn't do anything - the Update-Database command shows the No pending code-based migrations. message. Any ideas? Thanks.
Update:
I'm getting the following error message:
The DELETE statement conflicted with the REFERENCE constraint "FK_dbo.AppStatus_dbo.AppRegistrations_AppRegistrationId". The conflict occurred in database "MVCapp", table "dbo.AppStatus", column 'AppRegistrationId'.
I decided to work out the cascade delete problem in a separate sample project. I found the following blog & MSDN pages very useful.
http://blog.bennymichielsen.be/2011/06/02/entity-framework-4-1-one-to-one-mapping/
http://msdn.microsoft.com/en-us/library/gg671256%28v=VS.103%29.aspx
http://msdn.microsoft.com/en-us/library/gg671273%28v=VS.103%29.aspx
Using the Code First approach create the following Model.
public class Category
{
public int CategoryId { get; set; }
public string CategoryName { get; set; }
public virtual Book Book { get; set; }
}
public class Book
{
public int CategoryId { get; set; }
public string BookTitle { get; set; }
public string BookAuthor { get; set; }
public string BookISBN { get; set; }
public virtual Category Category { get; set; }
}
(I realize the entity names suggest one-to-many relationship, but I am trying to model 1-to-1 relationship, as in my original question at the top.)
So, in the above model each Category can only have one Book.
In your DbContext-derived class add the following.
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
modelBuilder.Entity<Book>()
.HasKey(t => t.CategoryId);
modelBuilder.Entity<Category>()
.HasRequired(t => t.Book)
.WithRequiredPrincipal(t => t.Category)
.WillCascadeOnDelete(true);
}
(The following namespaces are required for the above code: System.Data.Entity, System.Data.Entity.ModelConfiguration.Conventions.)
This properly creates the 1-to-1 relationship. You'll have a primary key in each table and also a foreign key in Book table with ON DELETE CASCADE enabled.
In the above code, on the Category entity I used WithRequiredPrincipal() with t => t.Category argument, where the argument is the foreign key column in the dependent table.
If you use WithRequiredPrincipal() without an argument you'll get an extra column in the Book table and you'll have two foreign keys in the Book table pointing to CategoryId in Category table.
I hope this info helps.
UPDATE
Later on I found answer directly here:
http://msdn.microsoft.com/en-us/data/jj591620#RequiredToRequired
A reason why you're not getting cascading delete is because your relationship is optional.
If you want the relationship required i.e. an AppRegistration has to have one Agreement you can use (cascading delete configured automatically):
public class Agreement
{
...
[Required]
public AppRegistration AppRegistration{ get; set; }
}
If you want the relationship to be optional with cascading delete you can configure this using Fluent API:
modelBuilder.Entity<AppRegistration>()
.HasOptional(a => a.Agreement)
.WithOptionalDependent()
.WillCascadeOnDelete(true);
I'm a NHibernate user and NHibernate allows me to create a very fine-grained model.
I'm porting an application from NHibernate to Entity Framework.
NHibernate allows me to define things like:
public class User : DomainEntity
{
public virtual Name Name { get; set; }
...
public virtual ICollection<LogonInformation> LogonInformations { get; set; }
}
public class Name
{
public virtual string FirstName { get; set; }
public virtual string LastName { get; set; }
}
public class LogonInformation
{
public virtual string Ip { get; set; }
public virtual DateTime Date { get; set; }
}
Where Name and LogonInformation are mapped as < componentes >.
In special case,when NHibernate is creating the database, creates the UserId in LogonInformation table.
How can I do this using EntityFramework 5?
I've tried using the Complex Types but it does not seems to work since I still get the following exception:
One or more validation errors were detected during model generation:
\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType
'LogonInformation' has no key defined. Define the key for this
EntityType.
\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet
'LogonInformations' is based on type 'LogonInformation' that has no
keys defined.
Your exception is complaining about LogonInformation not having a primary key. In order to establish a primary key you add the attribute Key to the property you want to be the primary key, for instance, if Ip is your primary key, your code would be:
public class LogonInformation
{
[Key]
public virtual string Ip { get; set; }
public virtual DateTime Date { get; set; }
}
UPDATE:
If you can't change LogonInformation you can set its primary key with Fluent-API (I don't like this way but it could solve your problem). In order to do that, you need to override the OnModelCreating method in your context like this:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<LogonInformation>().HasKey(logInfo => logInfo.Ip);
}