When I'm trying to create a migration, Entity Framework throws an error
Unable to determine the principal end of an association between the types 'WorkFlowState' and 'WorkFlowState'. The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations.
Code:
public class WorkFlowState
{
public Guid Id { get; set; }
public virtual WorkFlowState NextState { get; set; }
public virtual WorkFlowState PrevState { get; set; }
}
What should I do?
Update 1:
People are telling that the question is kind of duplicated question, but if you look at the accepted answer ( the third option which octavioccl provided ) you will see how it is different.
The problem is EF is trying to configure by convention an one-to-one relationship. If you check the link that was shared by #Michael in his comment, you will notice that you need to specify who is the principal end and who is the dependent end. When you are going to create a new instance of WorkflowState you must set always the principal end. Now, if you need to configure an one to one relationship, you will notice by that link you have two options:
Option 1: Specifying the FK of your relationship
public class WorkFlowState
{
public Guid Id { get; set; }
[Key,ForeignKey("PrevState")]
public Guid PrevStateId { get; set; }
public virtual WorkFlowState NextState { get; set; }
public virtual WorkFlowState PrevState { get; set; }
}
Option 2: Using the Required data annotation:
public class WorkFlowState
{
public Guid Id { get; set; }
public virtual WorkFlowState NextState { get; set; }
[Required]
public virtual WorkFlowState PrevState { get; set; }
}
But there is a third option in case you need both references as optional:
public class WorkFlowState
{
public Guid Id { get; set; }
[ForeignKey("PrevState")]
public Guid? PrevStateId { get; set; }
[ForeignKey("NextState")]
public Guid? NextStateId { get; set; }
public virtual WorkFlowState NextState { get; set; }
public virtual WorkFlowState PrevState { get; set; }
}
In this case you are going to create two unidirectional relationships. For help you understand better what happens in this last case, the Fluent Api configurations of these relationships would be this way:
modelBuilder.Entity<WorkFlowState>().HasOptional(t => t.NextState).WithMany().HasForeignKey(t => t.NextStateId);
modelBuilder.Entity<WorkFlowState>().HasOptional(t => t.PrevState).WithMany().HasForeignKey(t => t.PrevStateId);
Related
I have two classes:
Main class:
public class CCourseDetailModel
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int CourseDetailId { get; set; }
[ForeignKey("CourseOutcomes")]
public int CourseOutcomesId { get; set; }
public virtual CACourseOutcomesModel CourseOutcomes { get; set; }
}
Dependent class:
public class CACourseOutcomesModel
{
[Key, ForeignKey("CourseDetail")]
public int CourseOutcomesId { get; set; }
[Required]
public virtual CCourseDetailModel CourseDetail { get; set; }
}
I have 10 or so similar classes, with 1 to 1 relationships that work fine. This is the only one giving me the following error:
CACourseOutcomesModel_CourseDetail_Target: : Multiplicity is not valid in Role 'CACourseOutcomesModel_CourseDetail_Target' in
relationship 'CACourseOutcomesModel_CourseDetail'. Because the
Dependent Role properties are not the key properties, the upper bound
of the multiplicity of the Dependent Role must be ''.*
Any idea where I'm going wrong? Need a fresh set of eyes please. Thanks!
In a one to one relationship, one end must be principal and the another one must be dependent, so you can't have a FK property in both sides. Remove the FK property in the principal (CCourseDetailModel) and in CACourseOutcomesModel you don't need to use Required attribute. Using ForeignKey attribute you already are telling to EF who is the dependent end.
In Fluent Api would be:
modelBuilder.Entity<CACourseOutcomesModel>()
.HasRequired(p => p.CourseDetail)
.WithOptional(p => p.CourseOutcomes);
So your model should be this way:
public class CCourseDetailModel
{
[Key]
//[DatabaseGenerated(DatabaseGeneratedOption.Identity)] don't need this, it's the configuration by default.
public int CourseDetailId { get; set; }
public virtual CACourseOutcomesModel CourseOutcomes { get; set; }
}
public class CACourseOutcomesModel
{
[Key, ForeignKey("CourseDetail")]
public int CourseOutcomesId { get; set; }
public virtual CCourseDetailModel CourseDetail { get; set; }
}
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; }
}
I have two classes that relate to one another (one-to-many) and I thought I had the properties setup correctly, but when I run the Update-Database command for my migration, I get the following error:
Introducing FOREIGN KEY constraint
'FK_dbo.ParentEnrollment_dbo.CellGroup_CellGroupID' on table
'ParentEnrollment' 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 or index. See previous
errors.
My two classes:
[Table("CellGroup")]
public class CellGroup : BaseEntity
{
public Guid AcademicYearID { get; set; }
[ForeignKey("AcademicYearID")]
public virtual AcademicYear AcademicYear { get; set; }
public Guid LeaderID { get; set; }
[ForeignKey("LeaderID")]
public virtual Parent Leader { get; set; }
public Guid PreviousGroupID { get; set; }
[ForeignKey("PreviousGroupID")]
public virtual CellGroup PreviousGroup { get; set; }
public string Name { get; set; }
public int MaximumSize { get; set; }
public virtual ICollection<ParentEnrollment> Parents { get; set; }
}
and
[Table("ParentEnrollment")]
public class ParentEnrollment : BaseEntity
{
public Guid ParentID { get; set; }
[ForeignKey("ParentID")]
public virtual Parent Parent { get; set; }
public Guid AcademicYearID { get; set; }
[ForeignKey("AcademicYearID")]
public virtual AcademicYear AcademicYear { get; set; }
public bool FirstTimeEnrolling { get; set; }
public string HSLDAAccountNumber { get; set; }
public DateTime HSLDARenewalDate { get; set; }
public string CurrentChurch { get; set; }
public string CurrentChurchContact { get; set; }
public string CurrentChurchPhone { get; set; }
public Guid CellGroupID { get; set; }
[Required]
[ForeignKey("CellGroupID")]
public virtual CellGroup CellGroup { get; set; }
public bool VolunteerBuyOut { get; set; }
public Guid VolunteerPositionID { get; set; }
[ForeignKey("VolunteerPositionID")]
public virtual VolunteerPosition VolunteerPosition { get; set; }
public string VolunteerPositionNotes { get; set; }
public virtual ICollection<StudentEnrollment> StudentEnrollments { get; set; }
}
I only have the Parents property on the CellGroup class so I can easily access the list of enrollments in that cell group. I tried to remove the property to see if it cleared up the warning/error, but it did not. Can someone spot where I have gone wrong with my model(s)?
This error says that you cannot introduce a foreign key from table ParentEnrollment to table CellGroup that has cascading delete enabled, because this will create multiple cascade paths, which is not allowed on SQL Server.
According to the code you posted both tables have relations to a table Parent as well as AcademicYear, which are on non nullable FK columns, so EF will enable cascading on delete by default. With another FK from ParentEnrollment to CellGroup there would be multiple cascade paths, e.g. Parent to CellGroup to ParentEnrollment and Parent to ParentEnrollment, and this is causing your error. Removing the Parent property won't solve this because there still is the same cascading path problem starting from table AcademicYear.
So you have to disable cascading delete for your foreign key, which has to be done using Fluent API in your DbContext like this:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<ParentEnrollment>()
.HasRequired(m => m.CellGroup)
.WithMany(m => m.Parents)
.HasForeignKey(m => m.CellGroupID)
.WillCascadeOnDelete(false);
}
Is it possible to have a foreign key mapping based on a specific column value.
I have the following entities.
public class Controller
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public virtual List<ControllerDevice> ActiveDevices { get; set; }
public virtual List<ControllerDevice> TamperedDevices { get; set; }
public virtual List<ControllerDevice> IgnoredDevices { get; set; }
}
public class ControllerDevice
{
public int Id { get; set; }
public DeviceStatus Status { get; set; }
public int ControllerId { get; set; }
public int NetworkDeviceId { get; set; }
public virtual Controller Controller { get; set; }
public virtual NetowkDevice NetowkDevice { get; set; }
}
public class NetowkDevice
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
}
public enum DeviceStatus
{
Active,
Tampered,
Ignored
}
Is it possible to have the ActiveDevices, TamperedDevices and IngoredDevices list be auto populated based on ControllerDevice DeviceStatus, or would I have to create three different tables for each list. IE ActiveControllerDevice, TamperedControllerDevices and IgnoredControllerDevices.
Please let me know if you require further explanation.
Use single devices collection:
public class Controller
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public virtual List<ControllerDevice> Devices { get; set; }
}
...and filter it, when you need to process or display devices with specific Status value:
controller.Devices.Where(d => d.Status == DeviceStatus.Active);
Several tables for each devices status, and/or devices hierarchy (theoretically, you can solve this problem with a TPH inheritance) is a way to hell, because instead of single entity ControllerDevice with a status you'll get three entity types (ActiveControllerDevice, TamperedControllerDevice and IgnoredControllerDevice), which is not corresponding to model.
Instead of changing status, the device will change its type, and you cannot do that in simple way.
public class TestContext : DbContext
{
public TestContext()
{
Configuration.AutoDetectChangesEnabled = true;
Configuration.LazyLoadingEnabled = true;
Configuration.ProxyCreationEnabled = true;
Configuration.ValidateOnSaveEnabled = true;
}
public virtual DbSet<NetowkDevice> NetowkDevices{ get; set; }
public virtual DbSet<ControllerDevice> ControllerDevices{ get; set; }
public virtual DbSet<Controller> Controlleres{ get; set; }
}
http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/d0443029-2175-4bde-a834-4f8dbf313201/
Should I enable or disable dynamic proxies with entity framework 4.1 and MVC3?
Yes, you can do that. Enum support was introduced in Entity Framework 5, .Net Framework 4.5. In Entity Framework, an enumeration can have the following underlying types: Byte, Int16, Int32, Int64 , or SByte.
And you can filter like this:
context.ControllerDevices.Where(d => d.Status == DeviceStatus.Active);
More here: http://msdn.microsoft.com/en-us/data/hh859576.aspx
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);