I want to create a 1 to 1 relationship by code first, below is my code,
class Person
{
public int id { get; set; }
public string Name { get; set; }
public virtual PersonDetail detail { get; set; }
}
class PersonDetail
{
public int id { get; set; }
public double Height { get; set; }
public double Weight { get; set; }
public virtual Person person { get; set; }
}
class EFTest : DbContext
{
public DbSet<Person> personSet { get; set; }
public DbSet<PersonDetail> detailSet { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Person>().HasRequired(x => x.detail).WithRequiredPrincipal(x => x.person);
}
}
But I still can insert a person without person detail. I'm trying to create a 1 to 1 relationship in model first, it works well, if I insert one end without the other end, there will be an exception thrown. Why code first with the code above create a 1 to 0..1 relationship?
Anyone can help?
That is possible only if both Person and PersonDetail will be mapped to the same table (the mapping technique is called Table Splitting) because strict 1:1 means that you cannot insert Person without existing PersonDetail but you also cannot insert PersonDetail without existing Person => you cannot insert either of them because the dependency will be always missing (remember each record has its own insert command and database check the integrity after each command not after transaction).
Only when you use table splitting EF will create single insert command containing data from both entities. In your entity model it will look like two entities with 1:1 mapping but in database it will be single table.
Related
I am new to entity framework and I am using code first approach to create entities using TPT inheritance.
My requirement is to create the entities as per the attached diagram where ID is PK for Customers table and FK for the AddressDetails and ContactDetails table. Based on the keys I also need to create the association and navigation properties for the entities. Table Diagram
In my code I have created entities as
public class Customer
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public int ZipCode { get; set; }
public virtual ContactDetails ContactDetails { get; set; }
public virtual AddressDetails AddressDetails { get; set; }
}
[Table("ContactDetails")]
public class ContactDetails: Customer
{
public string MobileNo { get; set; }
public string EmailId { get; set; }
}
[Table("AddressDetails")]
public class AddressDetails: Customer
{
public string BillingAddress { get; set; }
public string DeliveryAddress { get; set; }
}
My question is, have I created the association and navigation properties correctly or do I need to add them in the ContactDetails and AddressDetails class as well? Also, when I run the code the entities are getting created in the database but for the Customer table there are 2 additional columns created as AddressDetails_Id(FK,int,null) and ContactDetails_Id(FK,int,null). I think they are created because of the navigation property but I do not need these columns in the database to be created. Also the values are always null in these two columns.
Any help would be appreciated. Thanks in advance.
I am trying to create one-to-many and reverse one-to-one relationship using code first. Here is what I ma trying to do
1) One-to-Many between two classes and it works as expected.
public class X
{
[Key]
public int XId { get; set; }
public ICollection<Y> Y { get; set; }
}
public class Y
{
[Key]
public int YId { get; set; }
public int XId { get; set; }
public X X { get; set; }
}
public class DataContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Y>()
.HasRequired(y => y.X)
.WithMany(x => x.Y)
.HasForeignKey(y => y.XId);
}
}
Now what I want to do is to create Reverse One-to-One optional relationship between Y and X, such that the X will contain a foreign key of Y...How is it possible? Here is what I am trying to do and it throws some Multiplicity Error
public class X
{
[Key]
public int XId { get; set; }
public ICollection<Y> Y { get; set; }
public int YId {get; set; }
[ForiegnKey("YId")]
public Y YOptional { get; set; }
}
public class Y
{
[Key]
public int YId { get; set; }
public int XId { get; set; }
public X X { get; set; }
public X XOptional {get; set; }
}
public class DataContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Y>()
.HasRequired(y => y.X)
.WithMany(x => x.Y)
.HasForeignKey(y => y.XId);
modelBuilder.Entity<X>()
.HasOptional(x => x.YOptional)
.WithOptionalDependent(y=> y.XOptional);
}
}
You can't have a relationship between two entities that is defined differently from either end. So you can't do 1:* from one direction and 1:1 from another.
Let me make a guess that you don't really want it to be 1:1 from the dependent end. From that end it will always only point to one thing.
In mappings, unlike in life, unless you have many to many, a child only has one parent.
You can, however, create a 0..1 : * relationaship (zero or one to many). Where the parent can have one or more children (e.g. "many") but the child can exist without a parent, but it can never have more than one parent (e.g. "zero or one").
Here is the simplest method of making your classes result in a [zero or one] to many relationship. Notice that I made the foreign key in the class Y a nullable int. WIth this setup, EF conventions will result in a mapping that lets a child exist without a parent.
public class X
{
[Key]
public int XId { get; set; }
public ICollection<Y> Y { get; set; }
}
public class Y
{
[Key]
public int YId { get; set; }
public int? XId { get; set; }
public X X { get; set; }
}
public class DataContext : DbContext
{
public DbSet<X> XSet { get; set; }
public DbSet<Y> YSet { get; set; }
}
Here is a screenshot of visual model derived from the above classes and context.
I think this achieves the behavior you are seeking if my guess that you may just be perceiving it differently is correct.
Using the actual class names you mentioned in the comments:
Mapping a User that can have many Singles is not a problem. However, when you want to map a 1:1 association between a User and a Single you have to choose which of the two is the "principle" entity. You can't have a foreign key column in both tables because one entity will always be inserted before the other one. The "dependent" entity is inserted next, and it refers to the principal's primary key value.
So if User is the principal entity, you could have a class model similar to this:
public class User
{
public User()
{
this.Singles = new HashSet<Single>();
}
public int UserId { get; set; }
public string Name { get; set; }
public Single Single { get; set; }
public virtual ICollection<Single> Singles { get; set; }
}
public class Single
{
public int SingleId { get; set; }
public string Name { get; set; }
public virtual User User { get; set; }
public int SuperUserId { get; set; }
public User SuperUser { get; set; }
}
And two options for mappings:
Option 1: User as principal
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<User>().HasMany(u => u.Singles)
.WithRequired(s => s.SuperUser).HasForeignKey(s => s.SuperUserId);
modelBuilder.Entity<User>().HasOptional(s => s.Single)
.WithOptionalPrincipal(s => s.User).Map(m => m.MapKey("UserId"));
}
In the data model, Single now has two foreign keys, UserId and SuperUserId. This is how to create a User and a Single in User.Single and User.Singles:
var superUser = new User { Name = "superUser1" };
var single = new Single { Name = "single" };
superUser.Singles.Add(single);
db.Users.Add(superUser);
superUser.Single = single;
db.SaveChanges();
And EF will first insert the User, then the Single having both foreign keys equal to the User's primary key.
Option 2: Single as principle
You can also make Single the principal entity in the 1:1 association:
modelBuilder.Entity<User>().HasOptional(s => s.Single)
.WithOptionalDependent(s => s.User).Map(m => m.MapKey("SingleId"));
Now there's only one foreign key in Single (SuperUserId) and a foreign key in User (SingleId). If you execute the same code, now EF will throw
Unable to determine a valid ordering for dependent operations.
This is because there is a chicken-and-egg problem: the Single must be created before the dependent User can be created, but the User must be created before the Single can be added to its Singles collection. This could be solved by assigning the Single later:
var superUser = new User { Name = "superUser1" };
var single = new Single { Name = "single" };
superUser.Singles.Add(single);
db.Users.Add(superUser);
db.SaveChanges();
superUser.Single = single;
db.SaveChanges();
You'd want to wrap this in a TransactionScope, so I think this option is less viable.
Note
As you see, in a 1:1 mapping the foreign key can't be mapped to a property in the class model. There is no HasForeignKey in the fluent API after WithOptionalDependent or WithOptionalPrincipal. Also, this association can only be mapped by the fluent API. In data annotations there is not attribute to indicate the principal end of an association.
I am using Entity Framework Database First, but I would like to replicate the following behavior from the Code First paradigm:
In Entity Framework Code First, you can do something along these lines:
public class Thing
{
public int ID { get; set; }
ICollection<Stuff> Stuffs { get; set; }
}
public class Stuff
{
public int ID { get; set; }
ICollection<Thing> Things { get; set; }
}
And the database will generate and Associative table to represent the many to many relationship.
I'm using Database First with a legacy database. I pulled in the entities and it included the associative table representing a many-to-many relationship between two of our tables.
Since the associative table is included as an entity, the navigation properties are as such:
public class Thing
{
public int ID { get; set; }
public ICollection<ThingStuff> ThingStuffs { get; set; }
}
public class ThingStuff
{
public int ThingID { get; set; }
public int StuffID { get; set; }
ICollection<Thing> Things { get; set; }
ICollection<Stuff> Stuffs { get; set; }
}
public class Stuff
{
public int ID { get; set; }
public ICollection<ThingStuff> ThingStuffs { get; set; }
}
So to navigate, I have to:
var stuff = Thing.ThingStuffs.Select(ts => ts.Stuff);
Instead of:
var stuff = Thing.Stuffs;
So The Question Is:
Is there any way to drop the entity representing the association (ThingStuff) and tell EntityFramework about the existing table to create the many-to-many navigation properties?
Wouldn't it be better if you map your composite keys, as stated in the fluent api documentation? http://msdn.microsoft.com/en-us/data/jj591617.aspx
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 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; }
}