I have an app that was created using EF. The problem is that I noticed some extraneous foreign keys columns created in one of the tables. Dropping these columns causes an [SqlException (0x80131904): Invalid column name 'Material_Id' error.
Here is a simplified version of the class structure...
public class Hazard
{
public int Id { get; set; }
public string Name { get; set; }
}
public abstract class HazardAnalysis
{
public int Id { get; set; }
public int HazardId { get; set; }
public virtual Hazard Hazard { get; set; }
}
public class ProductHazard : HazardAnalysis
{
public int ProductId { get; set; }
public virtual Product Product { get; set; }
}
The table that was generated looked like this...
dbo.Hazards
Id int
Name string
Product_Id int
Since the relationship between ProductHazards and Hazards is 1:many, the Product_Id field should not be there. Dropping this column generates the Invalid column name 'Product_Id' error.
I've scoured the model for hours and can't find any valid reason for this column to exist.
Is there any way to update the model after manually dropping a column? I obviously don't want to drop and recreate the database.
I've also noticed that the productId of the current product is inserted in the dbo.Hazards Product_Id table whenever a new ProductHazard is created. Since there is a many-to-one relationship between ProductHazards and Hazards, when a new ProductHazard is created, the Product_Id field is updated with the ProductId of the new ProductHazard, which seems bizarre.
Any advice would be greatly appreciated.
Here is the DbSet code:
public DbSet<Hazard> Hazards { get; set; }
public DbSet<HazardAnalysis> HazardAnalyses { get; set; }
and also...
modelBuilder.Entity<HazardAnalysis>()
.HasRequired(e => e.Hazard)
.WithMany()
.HasForeignKey(e => e.HazardId)
.WillCascadeOnDelete(false);
You need to define the many part of the relationship. In this case, you need to add a collection property to your Hazard object, like below:
public class Hazard
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<HazardAnalysis> HazardAnalyses { get; set; }
}
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();
I have an annoying problem that i can't seem to solve. Lets say i have a database with two tables.
Student
INT Id
NVARCHAR(30) Name
INT PrimaryTeacherId
INT SecondaryTeacherId
Teacher
INT Id
NVARCHAR(30) Name
Now when i set foreign key for PrimaryTeacherId and SecondaryTeacherId and use DatabaseFirst mapping in my project i get something like this for Student table
public partial class Student
{
public int Id { get; set; }
public string Name { get; set; }
public int PrimaryTeacherId { get; set; }
public int SecondaryTeacherId { get; set; }
public virtual Teacher Teacher { get; set; }
public virtual Teacher Teacher1 { get; set; }
}
Note the virtual part of the class and their names, Teacher and Teacher1. No matter how i call my FKs entity framework will just override it and set increment names. That's ok if i have one or two keys to the same table but when there is more it's easy to get lost and code looks kinda annoying having object names with numbers in them. I know i can change generated classes name in my solution but when i update model changes will be lost. I'm also using Metadata partial classes for generated classes (mostly for validation and display attributes), can i change name there maybe?
TLDR: I would like to have Teacher and Teacher1 have custom names, so something like this would be awesome
public partial class Student
{
public int Id { get; set; }
public string Name { get; set; }
public int PrimaryTeacherId { get; set; }
public int SecondaryTeacherId { get; set; }
public virtual Teacher PrimaryTeacher { get; set; }
public virtual Teacher SecondaryTeacher { get; set; }
}
I am trying to create some tables using Code First. Here is my code:
public class Country
{
[Key]
public int Id { get; set; }
public string CountryName { get; set; }
}
public class State
{
[Key]
public int Id { get; set; }
public string StateName { get; set; }
public int CountryId { get; set; }
public Country Country { get; set; }
}
public class Customer
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public int CountryId { get; set; }
public int StateId { get; set; }
public virtual Country Country { get; set; }
public virtual State State { get; set; }
}
public class ProductContext : DbContext
{
public DbSet<Country> Country { get; set; }
public DbSet<Customer> Customer { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
}
When I Execute this code the following error occurs:
Introducing FOREIGN KEY constraint
'FK_dbo.State_dbo.Country_CountryId' on table 'State' 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.
But I want the CountryId in State Table to be a foreign key. What am I missing here? Can anybody guide me the correct way of achieving this?
Entity Framework is worried about deletion here- because the User has a direct relationship to a Country and also a State and the State also relates to a Country you effectively have a potential loop of User -> State -> Country -> User which would mean that if cascade deletions were enabled the moment you deleted one user you would potentially delete everything in your database.
The answer is in the error message- by disabling cascade deletions across some of these relationships ( which is logical - deleting a user doesn't mean you want to delete their state and country ) you will avoid this risk. As you might imagine this has come up on SO before.
As an aside, having the Country on the User and also on the State looks like questionable denormalisation - there may be a good reason for it, but that happens less often than you would expect.
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 having an issue that i just can't seem to figure out. Lets say I have 2 Entities defined in my domain; Person and Document. Below is the definition for Document :
public class Document
{
public int Id { get; set; }
[Required]
[StringLength(255)]
public string Title { get; set; }
public DateTime Date { get; set; }
public virtual Person Owner{ get; set; }
public virtual Person AssignedTo { get; set; }
}
Now, when EF CTP4 creates the SQL table on initialize, there is only one field mapping to a Person.Id being Owner_id. Whatever i try, the field for AssignedTo is never created.
Anything that could solve this?
Regards,
avsomeren
Your code perfectly created the desired schema in the database for me:
If you don't get this schema in you DB then my guess is that something is not right with the rest of your object model. Could you post your full object model please?
Another Solution:
While your current Document class will give you the desired results, but you can still take advantage of the Conventions for Code First and explicitly specify the FKs for your navigation properties:
public class Document
{
public int Id { get; set; }
[Required][StringLength(255)]
public string Title { get; set; }
public DateTime Date { get; set; }
public int OwnerID { get; set; }
public int AssignedToID { get; set; }
public virtual Person Owner { get; set; }
public virtual Person AssignedTo { get; set; }
}
Code First will now infer that any property named <navigation property name><primary key property name> (e.g. OwnerID), with the same data type as the primary key (int), represents a foreign key for the relationship.
This essentially results to the same DB schema plus you have the FKs on your Document object as well as navigation properties which gives you ultimate flexibility to work with your model.