When using data annotations with EF4.1 RC is there an annotation to cause cascade deletes?
public class Category
{
public int Id { get; set; }
[Required]
public string Name { get; set; }
public ICollection<Product> Products { get; set; }
}
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public Category Category { get; set; }
}
Using this model the constraint generated is:
ALTER TABLE [Product] ADD CONSTRAINT [Product_Category]
FOREIGN KEY ([Category_Id]) REFERENCES [Categorys]([Id])
ON DELETE NO ACTION ON UPDATE NO ACTION;
If not how is it achieved?
Putting required on the Product table Category relationship field solves this
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
[Required] //<======= Forces Cascade delete
public Category Category { get; set; }
}
I like to turn off cascade delete by default (by removing the OneToManyCascadeDeleteConvention)
I was then hoping to add them back in via annotations, but was surprised that EF doesn't include a CascadeDeleteAttribute.
After spending way too long working around EF's ridiculous internal accessor levels, the code in this gist adds a convention that allows attributes to be used: https://gist.github.com/tystol/20b07bd4e0043d43faff
To use, just stick the [CascadeDelete] on either end of the navigation properties for the relationship, and add the convention in your DbContext's OnModeCreating callback. eg:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Add<CascadeDeleteAttributeConvention>();
}
And in your model:
public class BlogPost
{
public int Id { get; set; }
public string Title { get; set; }
public string Content { get; set; }
[CascadeDelete]
public List<BlogPostComment> Comments { get; set; }
}
Not sure on Data Annotations, but you can add it in the database by modifying the actual relationship.
Looks like the answer is no for data annotations:
http://social.msdn.microsoft.com/Forums/en-US/adonetefx/thread/394821ae-ab28-4b3f-b554-184a6d1ba72d/
This question appears to show how to do it with the fluent syntax, but not sure if that applies for 4.1 RC
EF 4.1 RC: Weird Cascade Delete
As an additional example to Tyson's answer, I use the [CascadeDelete] attribute like follows in an entity, which successfully adds the "Cascade" delete rule to the Parent-Child relation.
public class Child
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Key]
[SkipTracking]
public Guid Id { get; set; }
[CascadeDelete]
public virtual Parent Parent { get; set; }
[Required]
[ForeignKey("Parent")]
public Guid ParentId { get; set; }
}
Related
I have an Item data model:
[DataContract]
public class Item
{
[Key]
[DataMember]
public int ItemId { get; set; }
[DataMember]
public string Title { get; set; }
[DataMember]
public string Description { get; set; }
[DataMember]
public ICollection<ItemImage> Images { get; set; }
}
and it links to ItemImage table through ItemId as foreign key:
[DataContract]
public class ItemImage
{
[Key]
[DataMember]
public int ItemImageId { get; set; }
[Required]
[DataMember]
public int ItemId { get; set; }
[Required]
[DataMember]
public string ImageUrl { get; set; }
[ForeignKey("ItemId")]
public virtual Item Item { get; set; }
}
Everything works before I add the following code in
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<ItemImage>()
.HasRequired(ii => ii.Item)
.WithMany()
.HasForeignKey(ii => ii.ItemId)
.WillCascadeOnDelete(true);
}
After specify the cascade delete to true, the Images property in Item couldn't be loaded. Can someone help me figure out what is happening? Thanks a lot!
You have that problem because you have missed the configuration of the many end in your relationship:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<ItemImage>()
.HasRequired(ii => ii.Item)
.WithMany(i=>i.Images)
.HasForeignKey(ii => ii.ItemId)
.WillCascadeOnDelete(true);
}
The first time it worked because EF uses the Data Annotations that you have applied (like ForeignKey) and by default EF recognizes that you want to create a one-to-many relationship due to the navigation properties that you have in both entities.
In addition, if a foreign key on the dependent entity (ItemImage) is not nullable, then Code First by default sets cascade delete on the relationship, so if you want, you don't need to use the Fluen Api configuration, your relationship was already set with cascade delete.
One last thing, if you want your navigation properties be lazy loaded, then you need to declare them as virtual:
[DataContract]
public class Item
{
//...
[DataMember]
public virtual ICollection<ItemImage> Images { get; set; }
}
try adding "virtual" so that you would get
public virtual ICollection<ItemImage> Images { get; set; }
I have seen many examples of implementing a one to one relationship, but I failed doing mine, because the requirements are some kind different (Guid with database generated option, foreign key property and so on).
I have 2 classes (Bundesland, Programmkonfiguration) that have a 1:1 relationship (both ends are required in business sense) but cannot be joined into one table
Requirements to Bundesland:
Guid Id as Key but without a DatabaseGenerated Attribute
Navigation Property Programmkonfiguration
Bundesland.cs:
public class Bundesland
{
[Key]
public Guid Id { get; set; }
public virtual Programmkonfiguration Programmkonfiguration { get; set; }
}
Requirements to Bundesland
Guid Id as Key generated from Database
ForeignKey Property Bundesland_Id (needed with _ for interface)
Navigation Property Bundesland
Programmkonfiguration.cs:
public class Programmkonfiguration
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id { get; set; }
public Guid Bundesland_Id { get; set; }
public virtual Bundesland Bundesland { get; set; }
}
database schema should look like this
table Bundesland (Id)
table Programmkonfiguration (Id, Bundesland_Id)
Why I failed until now:
EF doesn’t recognize the relationship by itself
if I use either attributes (ForeignKey, Required) or fluent API and the mode builder is not failing, the foreign key property Programmkonfiguration.Bundesland_Id is never set, after context.SaveChanges()
If you want to help me, here are additional classes you may gonna need: https://gist.github.com/anonymous/9cb554cd864e3dbee1ac
I am using .NET 4.5(.1) with EF5, but I failed with EF6 too
Thanks in advance :)
You can use fluent configuration for this:
public class Bundesland
{
[Key]
[ForeignKey("Programmkonfiguration")]
public Guid Id { get; set; }
public virtual Programmkonfiguration Programmkonfiguration { get; set; }
}
public class BundesLandConfiguration: EntityTypeConfiguration<Bundesland>
{
public BundesLandConfiguration()
{
HasProperty(p=>p.Id)
HasRequired(p=>p.Programmkonfiguration).WithRequiredPrincipal(p=>p.Bundesland);
}
}
public class Programmkonfiguration
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id { get; set; }
public Guid Bundesland_Id { get; set; }
public virtual Bundesland Bundesland { get; set; }
}
public class ProgrammkonfigurationConfiguration: EntityTypeConfiguration<Programmkonfiguration>
{
public ProgrammkonfigurationConfiguration()
{
HasKey(p=>p.Id);
HasProperty(p=>p.Id)
HasProperty(p=>p.Bundesland_Id)
}
}
Do not forget to add this configurations to EntityModelConfigurations in db context.
Update: because property naming is against convention, you should add [ForeignKey] attribute as I added to property Id of Bundesland class.
I'm using ASP.NET MVC 4 Entity Framework 5 to generate a code first migration for a database structure of the below classes that have relationships between them. However I've encountered a problem where it's causing this error whenever I try to update my database from the migration:
Paste Bin of the migration file can be found here: http://pastebin.com/ngXacrKV
Error returned:
Introducing FOREIGN KEY constraint 'FK_dbo.Bookings_dbo.Rooms_RoomId' on table 'Bookings' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
Could not create constraint. See previous errors.
Bunk.cs
public class Bunk
{
[Key]
public int BunkId { get; set; }
public BunkStatus BunkStatus { get; set; }
[ForeignKey("Room")]
public int RoomId { get; set; }
public virtual Room Room { get; set; }
// Added for convenience
public virtual ICollection<Booking> Bookings { get; set; }
}
Room.cs
public class Room
{
[Key]
public int RoomId { get; set; }
public string RoomName { get; set; }
public Gender RoomGender { get; set; }
public RoomStatus RoomStatus { get; set; }
public virtual ICollection<Bunk> Bunks { get; set; }
// Added for convenience
public virtual ICollection<Booking> Bookings { get; set; }
}
Bookings.cs
public class Booking
{
[Key]
public int BookingId { get; set; }
//[ForeignKey("UserProfile")]
//public int UserProfileId { get; set; }
//public UserProfile UserProfile { get; set; }
[ForeignKey("Bunk")]
public int BunkId { get; set; }
public Bunk Bunk { get; set; }
public int Duration { get; set; }
[ForeignKey("Preferred_Room")]
public int RoomId { get; set; }
public Room Preferred_Room { get; set; }
public Decimal Price { get; set; }
public BookingStatus BookingStatus { get; set; }
}
What would the best work around be to remove this issue without causing too much disturbance to the original class structure. I'm not too worried about adding new joining tables as long as I can still access the code in a Lazy loading way in my controllers/view models.
you can try to specify Fluent API to set no cascade delete
public class YOURContext: DbContext{
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
// here is where fluent API goes.
// I suspected the error is EF wanting a NO cascade delete. Hence the suggestion to try
entity<Booking>.HasOptional(t => t.Bunk)
.WithOptionalPrincipal()
.WillCascadeOnDelete(false); // <<<<<< this is the option to try.
// you may also need to try the same with Preferred_Room as well.
If no cascade delete is required then in Database context class we can set cascade delete to false for all the relationships by overriding OnModelCreating method as given below. Default EF makes it cascade delete that is why you are getting exception of cycles or multiple delete path.
public class MyContext: DbContext
{
//db sets defined
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<PrimaryKeyTable>().HasMany(x => x.ChildTableCollection).WithRequired(x =>
Key).WillCascadeOnDelete(false);
//In your case
modelBuilder.Entity<Bunk>().HasMany(x => x.Bookings).WithRequired(x =>
x.BunkId).WillCascadeOnDelete(false);
// same for room if required.
}
}
I am a bit confused as to why I am getting this error:
Introducing FOREIGN KEY constraint 'FK_QuestionTerms_Terms_TermId'
on table 'QuestionTerms' may cause cycles or multiple cascade paths.
Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other
FOREIGN KEY constraints. Could not create constraint. See previous errors.
I have a class Question and a class Term, Questions may have any number of Terms associated with them, and Terms may have any number of Questions associated with them. So I am attempting to create a many to many relationship between the two. First I attempted to use convention, and I am allowing EntityFramework to create the database. This is the Question class
public class Question
{
public Guid Id { get; set; }
public int QuestionNumber { get; set; }
public string StatementHtml { get; set; }
public string AnswerHeaderHtml { get; set; }
public string NotesHtml { get; set; }
public Guid CategoryId { get; set; }
public Guid CourseId { get; set; }
public Guid QuestionTypeId { get; set; }
public Guid? SimulationId { get; set; }
public Guid? SimulationTabId { get; set; }
public ICollection<Term> Terms { get; set; }
public ICollection<ReferenceItem> ReferenceItems { get; set; }
}
And here is the Term Class
public class Term
{
public Guid Id { get; set; }
public string Name { get; set; }
public string StatementHtml { get; set; }
public string Authority { get; set; }
public Guid ProductId { get; set; }
public Product Product { get; set; }
public ICollection<Question> Questions { get; set; }
}
I have also attempted to override OnModelCreating as follows, both process result is the exact same error code.
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Question>()
.HasMany(q => q.Terms)
.WithMany(t => t.Questions)
.Map(x =>
{
x.MapLeftKey("QuestionId");
x.MapRightKey("TermId");
x.ToTable("QuestionTerms");
});
}
The problem is that a cacade delete would go back and forth between the tables.
For example first deleting term A which would delete question 1,2 and 3. Question 1 was also used in term B so term B must be deleted .....
It therefore stops you creating such constraints.
There is a good coverage of how to fix it here: Entity Framework 4.1 InverseProperty Attribute and ForeignKey
Edit
This could be a side effect of other problems. You should start with a much simpler model and then gradually build it up.
For example:
Why do you have both ProductId and product
Why CategoryId and not Category
...
Try adding it in your OnModelCreating() method
modelBuilder.Entity<Question>().HasRequired(oo => oo.Term).WithMany(oo => oo.Questions).WillCascadeOnDelete(false);
How do I store additional fields in the "link table" that is automagically created for me if I have two entities associated as having a many to many relationship?
I have tried going the "two 1 to many associations"-route, but I'm having a hard time with correctly configuring the cascading deletion.
Unless those extra columns are used by some functions or procedures at the database level, the extra columns in the link table will be useless since they are completely invisible at the Entity Framework level.
It sounds like you need to re-think your object model. If you absolutely need those columns, you can always add them later manually.
You will most likely need to expose the association in your domain model.
As an example, I needed to store an index (display order) against items in an many-to-many relationship (Project <> Images).
Here's the association class:
public class ProjectImage : Entity
{
public Guid ProjectId { get; set; }
public Guid ImageId { get; set; }
public virtual int DisplayIndex { get; set; }
public virtual Project Project { get; set; }
public virtual Image Image { get; set; }
}
Here's the mapping:
public class ProjectImageMap : EntityTypeConfiguration<ProjectImage>
{
public ProjectImageMap()
{
ToTable("ProjectImages");
HasKey(pi => pi.Id);
HasRequired(pi => pi.Project);
HasRequired(pi => pi.Image);
}
}
From Project Map:
HasMany(p => p.ProjectImages).WithRequired(pi => pi.Project);
Maps to the following property on project:
public virtual IList<ProjectImage> ProjectImages { get; set; }
Hope that helps
Ben
Suppose there is a many-to-many association between two types: User and Message, and the association class is defined as UserMessageLink with additional properties.
public class User {
public int Id {get;set;}
}
public class Message {
public int Id {get;set;}
}
//The many-to-many association class with additional properties
public class UserMessageLink {
[Key]
[Column("RecieverId", Order = 0)]
[ForeignKey("Reciever")]
public virtual int RecieverId { get; set; }
[Key]
[Column("MessageId", Order = 1)]
[ForeignKey("Message")]
public virtual int MessageId { get; set; }
public virtual User Reciever { get; set; }
public virtual Message Message { get; set; }
//This is an additional property
public bool IsRead { get; set; }
}