I am using Microsoft.AspNetCore.Identity to manage users in my WebApp. I derived an ApplicationUser as follows:
public class ApplicationUser : IdentityUser
{
public string TgUserName { get; set; }
}
Now I have another entity let's call it Player which is managed by an ApplicationUser.
public string Id { get; set; }
public string ApplicationUserId { get; set; }
I purposely do not want to create a property of type ApplicationUser and have to mess around with include statements when retrieving objects from the database. I do want to have a property that holds the primary key which I then use to retrieve those objects on demand.
How can I tell EF Core that ApplicationUserId is a foreign key to ApplicationUser.Id.
You can do that by using the fluent API. First you need to define the relationship using the appropriate Has / With call overloads, and then use the HasForeignKey to map the property as FK.
In this particular case (many-to-one, no navigation properties on both ends, explicit FK property) it should be something like this:
modelBuilder.Entity<Player>()
.HasOne<ApplicationUser>() // no reference navigation property
.WithMany() // no collection navigation property
.HasForeignKey(e => e.ApplicationUserId) // FK property
.IsRequired(); // remove this if the relationship is optional
For more info, see Relationships - Manual configuration, Foreign key, Required and optional relationships sections of the official EF Core documentation.
Related
In EF Core, when defining Relationships, one can either provide the necessary FK properties explicitly or not:
Explicit FK property:
public class Person
{
public Guid Id { get; set; }
public ICollection<ParentIdentity> Identities { get; set; }
...
}
public class PersonIdentity
{
public Guid Id { get; set; }
public PersonFK { get; set; } //Explicit Data storage FK field in System Logic Entity :-(
...
}
The relationship would be defined in Fluent API as follows:
model.HasMany(x => Identities) // Person can have multiple identities
.WithOne() // Identity does not need a Nav property back up to Person
.WithForeignKey(x => x.PersonFK) // Hardcoded the FK.
The upside is its eminently clarity of how it's hooked up.
The downside is the blurring of domains between system logic and storage -- in that the system entity now has Data storage specific attributes (PersonFK) that have nothing to do with system logic that developers should be concentrating on.
Shadow properties
The alternative is to let EF sort it out, using shadow properties, by not define an FK Property on the Entity:
public class Person
{
public Guid Id { get; set; }
public ICollection<ParentIdentity> Identities { get; set; }
...
}
public class PersonIdentity
{
public Guid Id { get; set; }
...
}
And define the relationship as follows:
model.HasMany(x => Identities) // Person can have multiple identities
.WithOne() // Identity does not need a Nav property back up to Person
//.WithForeignKey(x => x.PersonFK) // Don't provide an FK property
;
EF will step up and add a property to the db table named to the following convention:
<principal primary key property name>Id
//ie, will be created as `PersonId`
But let's say I want to change it to:
<principal primary key property name>FK
//ie, will be created as `PersonFK`
Question
How?
Foraging so far
In case it helps, I'm looking in the following direction:
I can see a SqlServerConventionSetBuilder that inherits from RelationalConventionSetBuilder that inherits from ProviderConventionSetBuilder.
ProviderConventionSetBuilder in turn calls
ForeignKeyIndexConvention
ForeignKeyPropertyDiscoveryConvention
ForeignKeyAttributeConvention
found some sparse documentation at https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.metadata.conventions.foreignkeyindexconvention?view=efcore-6.0
but not enough there to know where to look really.
Can someone point me in the right direction as to:
what convention to replace
how to replace it easily?
Thank you!
EF Core 3.0... I can't find a precise answer for this completely normal mapping.
Principal to Dependent with no back pointer to Principal, 1:0 relationship, a Type Object / Lookup table set up. The problem is that the Object Key Name "RunId" is different than the EFCore generated key name "ServiceRunId"
How can I use Fluent API to replace the [ForeignKey("aServiceRun")] annotation?
This is my current Fluent set up, but I don't know where to put the ForeignKey mapping.
aBuilder.Entity<ServiceRun>().HasKey(new string[] { "RunId "});
aBuilder.Entity<Service>().HasOne(s => s.aServiceRun);
Class Service {
public int ServiceId {get; set;}
[ForeignKey("aServiceRun")]
public int RunId { get; set; }
public virtual ServiceRun aServiceRun { get; set; }
}
Class ServiceRun {
public int RunId { get; set; }
public string description {get ;set; }
}
Tables:
Service {
ServiceId int
RunId int
}
SerivceRun {
RunId int
Description string
}
How can I use Fluent API to replace the [ForeignKey("aServiceRun")] annotation?
You are seeking for HasForeignKey fluent API. But in order to get access to it (and other relationship configuration APIs), you need to define the relationship by using Has{One|Many} followed by With{One|Many}. For one-to-one relationships you also need to provide the generic type argument to HasForeignKey:
When configuring the relationship with the Fluent API, you use the HasOne and WithOne methods.
When configuring the foreign key you need to specify the dependent entity type - notice the generic parameter provided to HasForeignKey in the listing below. In a one-to-many relationship it is clear that the entity with the reference navigation is the dependent and the one with the collection is the principal. But this is not so in a one-to-one relationship - hence the need to explicitly define it.
Note that the entity containing the FK is always the dependent, so with your model the ServiceRun is the principal, Service is the dependent, and the fluent configuration is a follows:
modelBuilder.Entity<Service>()
.HasOne(s => s.aServiceRun) // navigation property
.WithOne() // no navigation property
.HasForeignKey<Service>(s => s.RunId); // foreign key
I found my answer to the above problem - I had a back-pointing list on my ServiceRun object that was not configured or ignored. I decided to leave this here as another example. Perhaps it will provide some worth to someone.
This is a 1:0 from Service to ServiceRunType where table names and property/field names don't match perfectly.
Tables
ServiceRun { //Does not match object name
int Id,
string Desc
}
Service {
int Id,
int RunId //Does not match object
}
Objects
Class ServiceRunType{ //Does not match table name
public int Id {get; set;}
public String Desc {get; set;}
}
Class Service{
public int Id {get; set;}
public int RunTypeId {get; set;} //Does not match table
public virtual ServiceRunType aServiceRunType { get; set; }
}
Fluent Code
modelBuilder.Entity<ServiceRunType>()
.ToTable("ServiceRun", schema: "load")
.HasKey(new string[] { "Id" });
modelBuilder.Entity<Service>()
.ToTable("Service", schema: "load") //Had to specify schema
.HasKey(new string[] { "Id" });
modelBuilder.Entity<Service>()
.Property("RunTypeId")
.HasColumnName("RunId");
modelBuilder.Entity<Service>()
.HasOne(s => s.aServiceRunType)
.WithOne()
.HasForeignKey<Service>(s => s.RunTypeId);
I am trying to use EF Code First on an existing database. I first tried some of the reverse-engineering tools, but I ran into problems with that, so at the moment I am trying to hand-code some of the classes. I am having some trouble getting some of the foreign key relationships set up. Consider two tables. The first is called LocaleValueLookup:
public class LocaleValueLookup
{
public int Id { get; set; }
public Guid Guid { get; set; }
}
This table provides an Id for multi-language text held in a different table (that other table is not important for the purposes of this question). The second table is called SectionType, and it has an optional FK to LocaleValueLookup:
public class SectionType
{
public int EnumId { get; set; }
public string Name { get; set; }
public int? DefaultSectionTextLocaleValueLookupId { get; set; }
// Navigation property
public LocaleValueLookup DefaultSectionTextLocaleValueLookup { get; set; }
}
I have tried various things, including adding a [ForeignKey] attribute to the SectionType.LocaleValueLookup property, and various incantations in the DbContext.OnModelCreating() override, but when I query the DbContext, I can't get the DefaultSectionTextLocaleValueLookup to be anything but null. I can retrieve other objects from the context just fine, and I have verified that DefaultSectionTextLocaleValueLookupId is not null at least some of the time.
My OnModelBuilding() contains the following:
modelBuilder.Entity<LocaleValueLookup>()
.ToTable("LocaleValueLookup")
.HasKey(lvl => lvl.Id);
modelBuilder.Entity<LocaleValueLookup>().Property(lvl => lvl.Id).IsRequired();
modelBuilder.Entity<SectionType>()
.ToTable("SectionType")
.HasKey(st => st.EnumId);
modelBuilder.Entity<SectionType>().Property(st => st.EnumId).IsRequired();
A couple of other points:
I would prefer not to have a SectionType collection on the LocaleValueLookup object. LocaleValueLookup is a low-level class that a lot of other classes depend on, so to include a collection property on LocaleValueLookup for every other class that references it will make for an unwieldy class with a lot of collections on it that I don't need from a domain perspective.
I would prefer to do the mapping setup in DbContext.OnModelCreating() rather than using attributes on my model objects
Any help would be greatly appreciated!
It looks like your foreign key is nullable so that means an optional -> many relationship.
Could you try something like this:
modelBuilder.Entity<SectionType>()
.HasOptional(opt => opt.DefaultSectionTextLocaleValueLookup)
.WithMany() // no navigation on the other side
.HasForeignKey(fk => fk.DefaultSectionTextLocaleValueLookupId);
If you were to write a query like this you should get a value back:
var query =
from st in db.SectionTypes
where st.EnumId == 12345
select new
{
SectionType = st,
LocaleValue = st.DefaultSectionTextLocaleValueLookup
};
It will only be non-null if the foreign key has a value, obviously.
I am a newbie in the EF. I read http://msdn.microsoft.com/en-us/data/gg193958.aspx and still confused.
I have an existing database and I'm writing a Code First model. I have Operators table with op_code Char(6) Primary Key. In the Operator class I named it OperatorCode, e.g.
[Key]
[Column("op_code",TypeName = "char")]
[DisplayName("Operator")]
public virtual string OperatorCode { get; set; }
In several of my tables I have EnteredBy and in some ModifiedBy columns that are FK to the op_code.
Say, for the Clients table I have both of these fields.
So, I added to the Operator class at the bottom:
[InverseProperty("EnteredBy")]
public virtual ICollection<Client> ClientsEnteredBy { get; set; }
[InverseProperty("ModifiedBy")]
public virtual ICollection<Client> ClientsUpdatedBy { get; set; }
and I added the following into the Client class:
public virtual Operator EnteredBy { get; set; }
public virtual Operator ModifiedBy { get; set; }
and I am getting a run-time error about EnteredBy_OperatorCode and ModifiedBy_OperatorCode columns.
What should I fix /add to let EF know my column names?
Thanks in advance.
Your foreign column names in the database do not match the default convention for FK names which is NavigationPropertyName_PrimaryKeyNameinTargetClass. Because your navigation properties are called EnteredBy and ModifiedBy and the primary key property is called OperatorCode EF expects - according to the mentioned convention - EnteredBy_OperatorCode and ModifiedBy_OperatorCode as foreign key columns. But those do not exist in the database which is the reason for your exception. Instead your FK columns are EnteredBy and ModifiedBy.
So, to fix the problem you must override the convention.
If you don't have FK properties in your model use Fluent API:
modelBuilder.Entity<Operator>()
.HasMany(o => o.ClientsEnteredBy)
.WithRequired(c => c.EnteredBy) // or HasOptional
.Map(m => m.MapKey("EnteredBy")); // mapping for the FK column name
modelBuilder.Entity<Operator>()
.HasMany(o => o.ClientsUpdatedBy)
.WithRequired(c => c.ModifiedBy) // or HasOptional
.Map(m => m.MapKey("ModifiedBy")); // mapping for the FK column name
(With this mapping you can remove the InverseProperty attribute.)
An alternative approach is to expose the FKs as properties in the model. Rename the navigation properties and use their names for the FK properties. The mapping is then possible with data annotations.
In Client class:
[ForeignKey("EnteredByOperator")]
public string EnteredBy { get; set; }
[InverseProperty("ClientsEnteredBy")]
public virtual Operator EnteredByOperator { get; set; }
[ForeignKey("ModifiedByOperator")]
public string ModifiedBy { get; set; }
[InverseProperty("ClientsUpdatedBy")]
public virtual Operator ModifiedByOperator { get; set; }
And remove the InverseProperty attributes in the Operator class.
Instead of the data annotations you can also use Fluent API:
modelBuilder.Entity<Operator>()
.HasMany(o => o.ClientsEnteredBy)
.WithRequired(c => c.EnteredByOperator) // or HasOptional
.HasForeignKey(c => c.EnteredBy);
modelBuilder.Entity<Operator>()
.HasMany(o => o.ClientsUpdatedBy)
.WithRequired(c => c.ModifiedByOperator) // or HasOptional
.HasForeignKey(c => c.ModifiedBy);
If both relationships are required you will need to disable cascading delete for at least one of the relationships (append .WillCascadeOnDelete(false) at the end of one of the mappings), otherwise SQL Server will throw an error that multiple cascading delete paths between the tables are not allowed.
I would suggest to use the "alternative approach" (expose foreign keys as properties) because it is easier to work with in most cases.
When using Entity Framework Code First 4.3.1 it is possible to create relationships with a multiplicity of 1-to-1. That is, one entity on each end of the relationship.
It is possible to configure 1-to-1 relationships to be required-required or required-optional ^. However, when I switch between the two I do not see any differences in:
The database schema generated. I am targeting SQL Server 2008.
The runtime behaviour of EF.
As such, I am able to create a RequiredPrincipalAs record without a corresponding RequiredDependentAs record, despite the relationship being configured as required-required. This seems to contradict the documentation for HasRequired(...):
Configures a required relationship from this entity type. Instances of the entity type will not be able to be saved to the database unless this relationship is specified. The foreign key in the database will be non-nullable.
http://msdn.microsoft.com/en-us/library/gg671317
The required-required relationship entities:
public class RequiredPrincipalA
{
public int Id { get; set; }
public virtual RequiredDependentA DependentA { get; set; }
}
public class RequiredDependentA
{
public int Id { get; set; }
public virtual RequiredPrincipalA PrincipalA { get; set; }
}
The required-optional relationship entities:
public class RequiredPrincipalB
{
public int Id { get; set; }
public virtual OptionalDependentB DependentB { get; set; }
}
public class OptionalDependentB
{
public int Id { get; set; }
public virtual RequiredPrincipalB PrincipalB { get; set; }
}
The DbContext and model configuration:
public class AppContext : DbContext
{
public DbSet<RequiredPrincipalA> PrincipalAs { get; set; }
public DbSet<RequiredDependentA> DependentAs { get; set; }
public DbSet<RequiredPrincipalB> PrincipalBs { get; set; }
public DbSet<OptionalDependentB> DependentBs { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<RequiredPrincipalA>()
.HasRequired(o => o.DependentA)
.WithRequiredPrincipal(o => o.PrincipalA);
modelBuilder.Entity<RequiredPrincipalB>()
.HasOptional(o => o.DependentB)
.WithRequired(o => o.PrincipalB);
}
}
The test code:
Database.SetInitializer(new DropCreateDatabaseAlways<AppContext>());
using (var ctx = new AppContext())
{
ctx.Database.Initialize(force: false);
ctx.PrincipalAs.Add(new RequiredPrincipalA());
ctx.PrincipalBs.Add(new RequiredPrincipalB());
ctx.SaveChanges();
}
I am aware I could add a [Required] data attribute to the navigation properties of RequiredPrincipalA.DependentA and RequiredDependentA.PrincipalA. This would cause EF validation to prevent the scenario above. However, I do not want to do this because it also validates the navigation property is populated when updating an existing entity. This means the application has to pre-fetch the entity at the other end of the relationship for every update.
Why do I not see any difference in the behaviour of EF just when changing a relationship between required-required and required-optional?
^ Note that optional-optional is also supported but this doesn't form part of my question. There are obvious differences in the generated database schema and runtime behaviour when an optional-optional relationship is configured.
I don't know why required-required is allowed for this case but it cannot exist in the database because relation is build on primary keys. Required-required means that A cannot be inserted if related B doesn't exist and B cannot be inserted if related A doesn't exist => neither A or B can be inserted.
Database relation has always principal and dependent entity - principal can always exist without dependent.
Real required-required in EF can be achieved only when both A and B are mapped to the same table (table splitting) because in such case they are both inserted with single insert command.
Not really an answer but I have more to say than will fit in comments. But you know, I write 900 page books...it's just how I roll. :)
Oddly I would expect the fluent configuration to behave the same way as the data annotation and am confused that it's not doing it. (I've pinged Rowan Miller with a link to this thread to get his feedback.) And the behavior I mean is: validating the constraint during SaveChanges.
On the database side, I'm with Ladislav.In the model, EF defines the 1:1 using the keys of the related entities. But in the database, you can't have FKs in both tables, so only the dependent table in the database will require that constraint that it's PK maps to an existing PK in the principal table.
And finally, I understand your reason for not wanting EF to enforce the relationship if you aren't going to always deal with teh full graph. I think 1:1 relationships are the most confusing of the EF relationship mappings and I always find myself having to go back for reminders of the rules and how things should work.
Old question. But since EF6 is still used and even available for .Net standard and this issue can be a real nuisance, I think it's worth mentioning something I couldn't find in other answers.
It is true that both HasRequired - WithRequiredPrincipal and HasOptional - WithRequired produce the same database schema and the same runtime behavior. That is, with both mappings it's possible to save a principal without a dependent entity and to remove the dependent later. So much for HasRequired.
But there is a way to make EF validate the required relationship when creating the entities, which is by simply adding a [Required] attribute:
public class RequiredPrincipalA
{
public int Id { get; set; }
[Required] // <== here
public virtual RequiredDependentA DependentA { get; set; }
}
public class RequiredDependentA
{
public int Id { get; set; }
public virtual RequiredPrincipalA PrincipalA { get; set; }
}
As said, only when creating the entities. It's still possible to set RequiredPrincipalA.RequiredDependentA = null and save it successfully. But I think that, fortunately, the likelihood of that happening in code is far lower than forgetting to set the required dependent.