I have the following models:
public class SomeForm
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public IList<FacilityContactInformation> OriginatingFacilities { get; set; }
public IList<FacilityContactInformation> DestinationFacilities { get; set; }
}
public class FacilityContactInformation
{
public FacilityContactInformation()
{
Id = -1;
}
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
[MaxLength(50)]
public string Owner { get; set; }
}
I am using automatic migrations to gen and re-gen the database schema.
This generates the error "Foreign key 'FK_dbo.FacilityContactInformations_dbo.SomeForm_SomeForm_Id ' references invalid column 'SomeForm_Id' in referencing table 'FacilityContactInformations'.
Could not create constraint. See previous errors.
I suspect the root cause is that EF tries to generate a FK FK_dbo.FacilityContactInformations_dbo.SomeForm_SomeForm_Id for both lists
Is there any way to keep using automatic migrations, but get this to generate a FK that works? It would seem like the FK should include the list name and generate two properties on FacilityContactInformations OR should generate an intermediate table to join on.
When you have 2 navigational properties that link to the same class, you should override OnModelCreating method of your dbcontext class. Then add this code into the OnModelCreating:
modelBuilder.Entity<SomeForm>
.Hasmany<FacilityContactInformation>(x => x.OriginatingFacilities);
modelBuilder.Entity<SomeForm>
.Hasmany<FacilityContactInformation>(x => x.DestinationFacilities);
This is because EF cannot determine the correct keys if the nav. prop. link to the same class.
Related
I tried many different examples here, but i can't seem to figure out what i'm doing wrong.
I have a table with a history table to it. I have removed many of the fields to make it easier to watch. After my migration it works fine if i watch in PHPMyAdmin and watch the primaryKey there.
I want to be able to go context.ProductArtifactDocumentState.Histories so i can get all linked histories.
DBContext
//Composite Key
builder.Entity<ProductArtifactDocumentStateHistory>()
.HasKey(k => new { k.Version, k.ProductArtifactDocumentStateId});
Table
[Table("ProductArtifactDocumentsState")]
public partial class ProductArtifactDocumentState : BaseEntity
{
public virtual ICollection<ProductArtifactDocumentStateHistory> ProductArtifactDocumentStateHistories { get; set; }
}
History Table
[Table("ProductArtifactDocumentsState_History")]
public partial class ProductArtifactDocumentStateHistory
{
[Column("ProductArtifactDocumentStateId")]
public int ProductArtifactDocumentStateId { get; set; }
public virtual ProductArtifactDocumentState ProductArtifactDocumentState { get; set; }
public int Version { get; set; }
}
The error i get:
System.InvalidOperationException: 'The entity type 'ProductArtifactDocumentStateHistory' requires a primary key to be defined. If you intended to use a keyless entity type, call 'HasNoKey' in 'OnModelCreating'. For more information on keyless entity types, see https://go.microsoft.com/fwlink/?linkid=2141943.'
Why do you need all this headache? Are you trying to save 2 bytes on a primary key? But after this all your ef code will be a nightmare. Just add Id field
public partial class ProductArtifactDocumentStateHistory
{
[Key]
public int Id {get; set;}
.....
}
This is an existing .NET Core 3.1 project I inherited.
I have a class referring to a database table
public class SupportContract
{
public int Id { get; set; }
public DateTime StartDate { get; set; }
public int SupportContractStatusId { get; set; }
public virtual SupportContractStatus SupportContractStatus { get; set; }
}
and a sub table with a foreign key
public class SupportContractStatus
{
public int Id { get; set; }
public string SupportContractStatusName { get; set; }
}
This works fine I can get
supportContract.SupportContractStatus.SupportContractStatusName
But if I rename SupportContractStatusId to ContractStatusId in C# and the database, I get an error "SupportContractStatusId missing".
I cannot find any link between the column SupportContractStatusId and table SupportContractStatus anywhere in code nor is there any mention of the foreign key.
There is no link in the DbContext either.
Is this naming convention assumed by Entity Framework? How does the framework know of the foreign key?
Yes, the naming convention that EF expects by default is based on the class name, not the property name. It will look for ClassNameId or ClassName_Id. You can link the FK either through annotation or configuration.
I.e.
public int ContractStatusId { get; set; }
[ForeignKey("ContractStatusId")]
public virtual SupportContractStatus ContractStatus { get; set; }
Configuration is done through IEntityTypeConfiguration implementations or by implementing the OnModelCreating method in the DbContext and configuring the relationship within the modelBuilder. For occasional deviations from convention, the attribute approach can generally cover everything.
I'm trying to solve one puzzle, but with no luck so far.
I have an article (or blog post) and comment entities, they both have content. In order to support lazy loading for content (there is no need to load the content when I need to display a list of articles or comments) I decided to move content to separate table and organize one-to-one mapping. Here is an example of what I think:
public class Content {
[Key]
public int ID { get; set; }
public string RawContent { get; set; }
// a bunch of scalar properties, like content type and so on
}
public class BlogArticle {
[Key]
public int ID { get; set; }
public int ContentID { get; set; }
[ForeignKey(nameof(ContentID)]
public virtual Content Text { get; set; }
// other properties related to BlogArticle
}
public class Comment {
[Key]
public int ID { get; set; }
public int ContentID { get; set; }
[ForeignKey(nameof(ContentID)]
public virtual Content Text { get; set; }
// other properties related to comment
}
<...>
From first look it seems ok: I can create blog articles, comments and attach content (at first I insert content, obviously). Update works as well. However, deletion doesn't work: when I delete blog article or comment, content is not deleted (but I want to delete it when blog article or comment are deleted, not opposite).
From what I understand my biggest issue because of relationship direction: in my case, Content entity is principal end and BlogArticle and Comment are dependent ends. In order to solve the puzzle, I need to change principal/dependent relationship. Again, from what I understand in order to change relationship direction I need to have a foreign key in Content entity and use fluent API to describe who is parent (principal) and who is child (dependent) in one-to-one relationship. Since many tables (there might be other entities with content property) are pointing to Content table, it doesn't seem very easy. Am I correct in my understanding?
One possible solution I could imagine is to create multiple foreign keys in Content table and point to each related table:
public class Content {
[Key]
public int ID { get; set; }
public string RawContent { get; set; }
// foreign keys
public int BlogArticleID { get; set; }
public int CommentID { get; set; }
public int WebWidgetID { get; set; }
// other foreign keys if necessary
}
probably, foreign keys must be nullable (because only single foreign key is used at once). Then use Entity Framework fluent API to describe relationship directions and organize cascade delete. For me it looks ugly, but I have no other ideas.
My question: is my proposed solution good/reliable? Are there other options I can look at?
Thanks in advance!
All your thoughts are correct. And your proposed solution is the only way with traditional relational design. The drawback of course is the need of multiple mutually exclusive nullable FKs.
The other options I see are as follows:
(1) Using EF inheritance for the entities holding Content. e.g.
public abstract class EntityWithContent
{
[Key]
public int ID { get; set; }
public virtual Content Text { get; set; }
}
public class BlogArticle : EntityWithContent
{
// other specific properties
}
public class Comment : EntityWithContent
{
// other specific properties
}
and configured one-to-one relationship between Content (dependent) and EntityWithContent (principal) using either shared PK association or FK association.
But since EF Core currently supports only TPH strategy (i.e. all the derived entities share one and the same table with union of all fields), I won't recommend it.
(2) Making Content owned type.
This is closer to the intent, but unfortunately EF Core currently always loads the owned entity data along with the owner data (even if they are configured to be provided by different database tables), which is against your original goal, so I won't suggest that either.
(3) Using table splitting feature.
If the main goal is simple to support controlled (lazy/eager/explicit) loading and the Content is always required, then this might be the best solution so far.
It would require a bit more configuration, but at the end it will give you the original table design (single table per entity) with the desired loading behavior:
Model:
public abstract class Content
{
[Key]
public int ID { get; set; }
public string RawContent { get; set; }
// a bunch of scalar properties, like content type and so on
}
public class BlogArticle
{
[Key]
public int ID { get; set; }
public virtual BlogArticleContent Text { get; set; }
// other properties related to BlogArticle
}
public class BlogArticleContent : Content
{
}
public class Comment
{
[Key]
public int ID { get; set; }
public virtual CommentContent Text { get; set; }
// other properties related to comment
}
public class CommentContent : Content
{
}
Note that here Content class is not part of EF inheritance hierarchy, but simple base class with the common properties (abstract modifier is not strongly necessary). The actual derived classes might or might not define their own properties.
Configuration:
modelBuilder.Entity<BlogArticle>().ToTable("BlogArticles");
modelBuilder.Entity<BlogArticle>()
.HasOne(e => e.Text)
.WithOne()
.HasForeignKey<BlogArticleContent>(e => e.ID);
modelBuilder.Entity<BlogArticleContent>().ToTable("BlogArticles");
modelBuilder.Entity<Comment>().ToTable("Comments");
modelBuilder.Entity<Comment>()
.HasOne(e => e.Text)
.WithOne()
.HasForeignKey<CommentContent>(e => e.ID);
modelBuilder.Entity<CommentContent>().ToTable("Comments");
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'm new to Entity Framework and C#/.Net and trying to create a TPH inheritance model, I'm not sure if I should be or not, so if not, please advise,
Here's the model:
public abstract class Vote
{
public int VoteID { get; set; }
public int UserID { get; set; }
public bool Value { get; set; }
public DateTime DateCreated { get; set; }
public User User { get; set; }
}
public class ProjectVote_ : Vote
{
public int ProjectID { get; set; }
public virtual Project Project { get; set; }
}
public class CommentVote_ : Vote //There are three more like this, votes for different hings
{
public int CommentID { get; set; }
public virtual Comment Comment { get; set; }
}
Now the Project model (comment and model is similar)
public class Project
{
public int ProjectID { get; set; }
public string Title { get; set; }
public virtual ICollection<Vote> Vote { get; set; }
}
What happens is that ICollection creates a database column Project_ProjectID as the foreign key in the Vote table (I think) instead of using the ProjectID I defined. How do I fix it or should I model it differently. If the fluent API is the way to fix it, I don't know how to do that.
In the end I want to be able to use one table to store 5 different types of votes.
When you have related entities you don't need to have a property to store the FK in your model. Entity framework knows that it needs to make a FK to the Project table in ProjectVote when it detects Project in your ProjectVote_ model. Same thing with User and UserId and Comment and CommentId. You don't need to have a property that stores the FK in your model.
You are getting the FK column with the name you don't like "Project_ProjectID" because Entity framework is detecting that it needs to create a FK for your navigation property "Project". It's using it's own naming convention to create the column hence "Project_ProjectID".
If you want to provide your own name for the column override OnModelCreating in your DBContext class and add this fluent mapping.
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Project>()
.HasMany(p => p.Vote)
.HasRequired(v => v.Project) //or .WithOptional(v => v.Project)
.Map(m => m.MapKey("ProjectId")); //or any other name you want.
}
And for the future this is a helpful reference for how to use the Fluent API. For example here is some documentation on how to custimize TPH with fluent.
Hope that helps!