I have two models:
public class User
{
.....
public virtual UserProfile UserProfile { get; set;}
}
public class UserProfile
{
.....
public virtual User User { get; set;}
}
The User is the master table and the relation is one to one. One user has only one UserProfile.
How can I define the relationship between User and UserProfile using EF CodeFirst Fluent API in such a way that when I delete one user from User table the user profile from Userprofile is also deleted?
Use WillCascadeOnDelete
modelBuilder.Entity<UserProfile>()
.HasKey(c => c.Id)
.HasRequired(c => c.User)
.WithRequiredDependent(c => c.UserProfile)
.WillCascadeOnDelete(true);
Related
Given a database with a table A. I want to create a table B and add a one-to-may relation between A and B with a required foreign key.
For example suppose that have an existing table 'Users' and then we want to add 'Roles' to the existing users.
The code first definition of those entities is as follows:
public class User
{
public Id UserId { get; set; }
public string Email { get; set; }
public string UserName => Email;
public Roles Role { get; set; }
public int? RoleId { get; set; }
}
public class Roles
{
public string RoleName { get; set; }
public int RoleId { get; set; };
public ICollection<User> GetUsers { get; set; }
}
The Configure Method for the Users using Fluent API is as follows:
public void Configure(EntityTypeBuilder<User> builder)
{
builder.ToTable("User");
builder.HasKey(t => t.UserId );
builder.Property(t => t.UserId ).ValueGeneratedOnAdd();
builder.HasOne(dt => dt.Role)
.WithMany(d => d.GetUsers)
.HasForeignKey(dt => dt.RoleId)
.HasConstraintName("ForeignKey_UserRole")
.OnDelete(DeleteBehavior.Restrict)
.IsRequired();
}
Trying to run the migration I got this error message:
'The ALTER TABLE statement conflicted with the FOREIGN KEY constraint'
By splitting this migration in two migrations and seeding the data between the them allowed me to build the new database:
The first one remove the constrain IsRequired on the Fluent APi definition of the User entity and allowing null value for the foreign key RoleId.
Then Seed the database
Add the second and last migration to enable the constrain of the required foreign key RoleID in the User entity and removing the allows null on the foreign key.
My question is related to if there is an strategy that allows to add a new relation using code first approach with a required foreign key using only one migration?
Thank you
Francisco
I have a User model and a Event model in my project. The Event has a creator(User) and has participant(Users) so Event has a one-to-many relationship with User and also a many-to-many relationship to the same table.
I had first the one-to-many relationship like this:
Public class Event
{
...
public int CreatedById { get; set; }
public virtual User CreatedBy { get; set; }
...
}
Then when I added the many-to-many relationship the migration doesn't generate the many to many relationship:
Public class User
{
...
public virtual ICollection<Event> Events { get; set; }
...
}
Public class Event
{
...
public int CreatedById { get; set; }
public virtual User CreatedBy { get; set; }
public virtual ICollection<User> Users { get; set; }
...
}
If I remove the one-to-many relationship then the migration generates the many-to-many relationship successfully.
Is there a way to do this with only data annotations?
EF doesn't know where User.Events has to be mapped to. It could be Event.CreatedBy or it could be Event.Users. Both would result in a valid model. You must give EF a little hint what you want by applying the [InverseProperty] attribute:
public class User
{
...
[InverseProperty("Users")]
public virtual ICollection<Event> Events { get; set; }
...
}
With Code First Approach, I would always recommend to use fluent API rather than using DataAnnotations, Which uses some conversions automatically.
This way, you'll know what exact configuration you've made.
If I were you, here is what i would use :
public class EventMap : EntityTypeConfiguration<Event>
{
public EventMap()
{
this.HasRequired(m => m.CreatedBy) // envent must have a creator
.WithMany() // a user can have 0,1 or more events created by him
.HasForeignKey(m => m.CreatedById) // specify property to be used as FK
.WillCascadeOnDelete(true); // delete all events created by user if that specific user is deleted
this.HasMany(m=>m.Users) // an event can have 0,1 or more participants
.WithMany(m=>m.Events) // a user can be a participant in 0,1 or more events
.Map(m => m.MapLeftKey("EventId").MapRightKey("UserId")); // this will generate intermediate table to hold participant information - dbo.EventUser with EventId & UserId
// Cascade Delete is always true for Many to Many mapping. however, it doesn't delete entry in other table, it deletes entry in Joined Table only.
}
}
I have a question.
I have these two tables:
The principal table is User with Customer dependence.
The reverse engineer code first generated classes as follows:
public class User
{
public User()
{
this.Customers = new List<Customer>();
}
...
public virtual ICollection<Customer> Customers { get; set; }
}
public class Customer
{
public Customer()
{
}
...
public int UserID { get; set; }
public virtual User User { get; set; }
}
I made the following modification in the user class:
public class User
{
public User()
{
}
public int CustomerID { get; set; }
public virtual Customer Customer { get; set; }
}
Because the relationship is One-to–Zero-or-One.
The original mapping is this:
// Relationships
this.HasRequired(t => t.User)
.WithMany(t => t.Customers)
.HasForeignKey(d => d.UserID);
And the modified mapping is this :
this.HasRequired(t => t.User)
.WithOptional(t => t.Customer)
.Map(m => m.MapKey("UserID"));
Is That correct?
If not, how would this mapping?
Thanks.
No, it's not correct.
The best thing you can do - supposed you can change the database schema - is removing the UserID foreign key from the Customer table and then create the relationship in the database between the two primary keys so that Customer.CustomerID is the foreign key in the association.
Reverse Engineering should then automatically create the expected one-to-one relationship, like so:
public class Customer
{
public int CustomerID { get; set; }
public virtual User User { get; set; }
//...
}
public class User
{
public int UserID { get; set; }
public virtual Customer Customer { get; set; }
//...
}
//...
this.HasRequired(t => t.User)
.WithOptional(t => t.Customer);
If you can't change the database schema, your best bet is to only remove the collection ICollection<Customer> Customers from the User class and keep the relationship as one-to-many.
The reason for all this is that EF only supports shared primary key one-to-one associations, but not foreign key one-to-one associations. (The latter one you can only "fake" by removing the collection, but it's still one-to-many from EF viewpoint.)
You can read more about one-to-one associations with EF and its limitations here:
One-to-one Shared Primary Key Associations
One-to-one Foreign Key Associations
I am trying to figure out how to make this work in EF. I have two entities Employee and User. I need to make it so the User has an optional mapping to the Employee. If there is a mapping, then it would be 1:1.
Basically this system can be accessed by employees and also by outside vendors, but I want one table to manage logons: Users.
How do I define this realtionship in EF with fluid configurations?
You just need to set simple fluent configuration:
modelBuilder.Entity<User>()
.HasOptional(u => u.Employee)
.WithRequired(e => e.User);
or in reverse order:
modelBuilder.Entity<Employee>()
.HasRequired(e => e.User)
.WithOptional(u => u.Employee);
EF will use Employess's PK as FK to user - that is mandatory requirement for EF to correctly use one-to-one relation. In case of Data annotation it is enough to mark Employee's PK with ForeignKey attribute pairing it with User navigation property:
public class Employee {
[Key, ForeignKey("User")]
public int Id { get; set; }
public virtual User User { get; set; }
}
public class User
{
...
public virtual Employee Employee { get; set; }
}
This tutorial may help.
I would like to enable CASCADE DELETE on a table using code-first. When the model is re-created from scratch, there is no CASCADE DELETE set even though the relationships are set-up automatically. The strange thing is that it DOES enable this for some tables with a many to many relationship though, which you would think it might have problems with.
Setup:
Table A <- Table B.
Table B's FK points to Table A's PK.
Why would this not work?
Possible reason why you don't get cascading delete is that your relationship is optional. Example:
public class Category
{
public int CategoryId { get; set; }
}
public class Product
{
public int ProductId { get; set; }
public Category Category { get; set; }
}
In this model you would get a Product table which has a foreign key to the Category table but this key is nullable and there is no cascading delete setup in the database by default.
If you want to have the relationship required then you have two options:
Annotations:
public class Product
{
public int ProductId { get; set; }
[Required]
public Category Category { get; set; }
}
Fluent API:
modelBuilder.Entity<Product>()
.HasRequired(p => p.Category)
.WithMany();
In both cases cascading delete will be configured automatically.
If you want to have the relationship optional but WITH cascading delete you need to configure this explicitely:
modelBuilder.Entity<Product>()
.HasOptional(p => p.Category)
.WithMany()
.WillCascadeOnDelete(true);
Edit: In the last code snippet you can also simply write .WillCascadeOnDelete(). This parameterless overload defaults to true for setting up cascading delete.
See more on this in the documentation
modelBuilder
.Entity<Product>()
.HasRequired(p => p.Category)
.WithMany(x => x.Products)
.WillCascadeOnDelete(true);