I have the following Entity class definition:
[Table("Users")]
public class WebUser
{
public virtual int Id { get; set; }
public virtual ICollection<Client> Clients { get; set; }
// more properties...
}
Notice that table name is different than the class name. I also have a ClientUsers table which is a many-to-many mapping for clients and users. Problem is, when I try to access the webUser.Clients property I get the following exception:
"Invalid object name 'dbo.ClientWebUsers'."
Looks like Entity Framework is trying to guess the name of the third table, but it apparently was not smart enough to take into account the table attribute that I have there. How can I tell EF that it is ClientUsers and not ClientWebUsers? Also what rule does it follow to know which table name comes first and which one comes second in the new table name? I think it's not alphabetical order.
I'm using EF 5.0. Thanks!
From the looks of things you're using Code First, so I'll answer accordingly. If this is incorrect, please let me know.
I believe the convention being used to determine the name of the many-to-many table is determined by the order in which they occur as DbSet properties in your SomeContext : DbContext class.
As for forcing EntityFramework to name your table whatever you like, you can use the Fluent API in the OnModelCreating method of your SomeContext : DbContext class as follows:
public class DatabaseContext : DbContext
{
public DatabaseContext()
: base("SomeDB")
{
}
public DbSet<WebUser> Users { get; set; }
public DbSet<Client> Clients { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<WebUser>().HasMany(c => c.Clients)
.WithMany(p => p.WebUsers).Map(
m =>
{
m.MapLeftKey("ClientId");
m.MapRightKey("UserId");
m.ToTable("ClientUsers");
});
}
}
This assumes your classes are something like the following:
[Table("Users")]
public class WebUser
{
public virtual int Id { get; set; }
public virtual ICollection<Client> Clients { get; set; }
// more properties...
}
public class Client
{
public int Id { get; set; }
public ICollection<WebUser> WebUsers { get; set; }
// more properties
}
Finally, here's an integration test (NUnit) demonstrating the functionality working. You may need to drop your database before running it as Code First should want to update/migrate/recreate it.
[TestFixture]
public class Test
{
[Test]
public void UseDB()
{
var db = new DatabaseContext();
db.Users.Add(new WebUser { Clients = new List<Client> { new Client() } });
db.SaveChanges();
var webUser = db.Users.First();
var client = webUser.Clients.FirstOrDefault();
Assert.NotNull(client);
}
}
Edit: Link to relevant documentation for the Fluent API
Rowan's answer (adding here for reference):
Here is the information on how to configure a many-to-many table (including specifying the table name). The code you are after is something like:
modelBuilder.Entity<WebUser>()
.HasMany(u => u.Clients)
.WithMany(c => c.WebUsers)
.Map(m => m.ToTable("ClientUsers");
~Rowan
Related
I am trying to separate my contexts using DDD. I have two domains, Instruments and Advertisements with its aggregate roots (the example is hypothetical). Instrument AR owns many InstrumentPictures and I would like to have that information in the Advertisement domain as well via proxy entity.
To ensure good database integrity it would be better to create foreign key from AdvertisementPicture.Guid to InstrumentPicture.Guid but as far as I know this can be done only through HasOne/HasMany model configuration.
Am I using the owner relationship wrong?
(Note: I do not want to configure the FK with custom sql migration.)
Instrument AR:
public class Instrument
{
protected Instrument()
{
}
public Instrument(string name, IEnumerable<InstrumentPicture> pictures)
{
Name = name;
_instrumentPictures.AddRange(pictures);
}
protected List<InstrumentPicture> _instrumentPictures = new List<InstrumentPicture>();
public IReadOnlyCollection<InstrumentPicture> InstrumentPictures
=> _instrumentPictures.AsReadOnly();
public Guid Guid { get; private set; }
public string Name { get; private set; }
}
InstrumentPicture owned collection:
public class InstrumentPicture
{
protected InstrumentPicture()
{
}
public InstrumentPicture(Guid guid, string url)
{
Guid = guid;
Url = url;
}
public Guid Guid { get; set; }
public string Url { get; set; }
public DateTime Created { get; set; }
}
Advertisiment AR
public class Advertisement
{
protected Advertisement()
{
}
public Advertisement(Guid instrumentGuid, string name, IEnumerable<AdvertisementPicture> pictures)
{
InstrumentGuid = instrumentGuid;
Name = name;
_advertisementPictures.AddRange(pictures);
}
protected List<AdvertisementPicture> _advertisementPictures = new List<AdvertisementPicture>();
public IReadOnlyCollection<AdvertisementPicture> AdvertisementPictures
=> _advertisementPictures.AsReadOnly();
public Guid Guid { get; private set; }
public Guid InstrumentGuid { get; private set; }
public string Name { get; private set; }
}
AdvertisementPicture proxy
public class AdvertisementPicture
{
protected AdvertisementPicture()
{
}
public AdvertisementPicture(Guid guid, string url)
{
Guid = guid;
Url = url;
}
public Guid Guid { get; set; }
public string Url { get; set; }
}
Model configuration:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Instrument>()
.HasKey(e => e.Guid);
modelBuilder.Entity<Instrument>()
.OwnsMany(e => e.InstrumentPictures, pic =>
{
pic.HasKey(e => e.Guid);
});
modelBuilder.Entity<Advertisement>()
.HasKey(e => e.Guid);
modelBuilder.Entity<Advertisement>()
.HasOne<Instrument>()
.WithMany()
.HasForeignKey(e => e.InstrumentGuid);
modelBuilder.Entity<Advertisement>()
.OwnsMany(e => e.AdvertisementPictures, pic =>
{
pic.HasKey(e => e.Guid);
// How can I add a foreign key to original InstrumentPicture for database integrity?
});
}
I've been struggling with this for hours and finding lots of answers on SO saying this isn't possible. Turns out this is possible using EntityFrameworkCore so I'll post what I've found on my Top Google Search for this problem.
As soon as you add a foreign key you will find the migration tool attempting to create the table in the second DBContext (unless you add ModelBuilder.Ignore<>() which will either do nothing or ignore your foreign key depending on your order of operations).
You can however do something like this:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<IdentityUser>()
.ToTable("AspNetUsers", t => t.ExcludeFromMigrations());
}
This will allow you to reference tables in other DBContext's but exclude any changes to them from the one you're working in. This is outlined in the MS documentation here.
If you have used Fluent API you may still need to apply those configurations in the referencing DB Context. This is easily achieved if you have used the IEntityTypeConfiguration<T> implementation by an additional call to ModelBuilder.ApplyConfigurationsFromAssembly(typeof(T).Assembly);.
In such a use case as above you may find yourself excluding a lot of different entities from your DB context. If you have these defined in their own library like I have to follow a DDD pattern you may find an extension method useful to exclude all of them at once:
public static class ExcludeEntitiesInAssemblyFromMigrationsExtension
{
public static void ExcludeEntitiesInAssemblyFromMigrations(this ModelBuilder builder, Assembly assembly)
{
var assemblyTypes = assembly.GetExportedTypes().Where(t => t.IsClass && !t.IsAbstract);
foreach (var assemblyType in assemblyTypes)
{
var entityBuilder = builder.Entity(assemblyType);
var entityTablename = entityBuilder.Metadata.GetTableName();
if (entityTablename != null)
{
entityBuilder.ToTable(entityTablename, t => t.ExcludeFromMigrations());
}
}
}
}
I'm trying to fetch (in disconnected way) an entity with its all related entities and then trying to update the entity. But I'm getting the following error:
Attaching an entity of type 'Feature' failed because another entity of the same type already has the same primary key value.
public class Person
{
public int PersonId { get; set; }
public string Personname { get; set }
public ICollection Addresses { get; set; }
}
public class Address
{
public int AddressId { get; set; }
public int PersonId { get; set; }
public string Line1 { get; set; }
public string City { get; set; }
public string State { get; set; }
public Person Person { get; set; }
public ICollection<Feature> Features { get; set; }
}
// Many to Many: Represented in database as AddressFeature (e.g Air Conditioning, Central Heating; User could select multiple features of a single address)
public class Feature
{
public int FeatureId { get; set; }
public string Featurename { get; set; }
public ICollection<Address> Addresses { get; set; } // Many-To-Many with Addresses
}
public Person GetCandidate(int id)
{
using (MyDbContext dbContext = new MyDbContext())
{
var person = dbContext.People.AsNoTracking().Where(x => x.PersonId == id);
person = person.Include(prop => prop.Addresses.Select(x => x.Country)).Include(prop => prop.Addresses.Select(x => x.Features));
return person.FirstOrDefault();
}
}
public void UpdateCandidate(Person newPerson)
{
Person existingPerson = GetPerson(person.Id); // Loading the existing candidate from database with ASNOTRACKING
dbContext.People.Attach(existingPerson); // This line is giving error
.....
.....
.....
}
Error:
Additional information: Attaching an entity of type 'Feature' failed because another entity of the same type already has the same primary key value.
It seems like (I may be wrong) GetCandidate is assigning every Feature within Person.Addresses a new instance. So, how could I modify the GetCandidate to make sure that the same instance (for same values) is bing assisgned to Person.Addresses --> Features.
Kindly suggest.
It seems like (I may be wrong) GetCandidate is assigning every Feature within Person.Addresses a new instance. So, how could I modify the GetCandidate to make sure that the same instance (for same values) is bing assisgned to Person.Addresses --> Features.
Since you are using a short lived DbContext for retrieving the data, all you need is to remove AsNoTracking(), thus allowing EF to use the context cache and consolidate the Feature entities. EF tracking serves different purposes. One is to allow consolidating the entity instances with the same PK which you are interested in this case, and the second is to detect the modifications in case you modify the entities and call SaveChanges(), which apparently you are not interested when using the context simply to retrieve the data. When you disable the tracking for a query, EF cannot use the cache, thus generates separate object instances.
What you really not want is to let EF create proxies which hold reference to the context used to obtain them and will cause issues when trying to attach to another context. I don't see virtual navigation properties in your models, so most likely EF will not create proxies, but in order to be absolutely sure, I would turn ProxyCreationEnabled off:
public Person GetCandidate(int id)
{
using (MyDbContext dbContext = new MyDbContext())
{
dbContext.Configuration.ProxyCreationEnabled = false;
var person = dbContext.People.Where(x => x.PersonId == id);
person = person.Include(prop => prop.Addresses.Select(x => x.Country)).Include(prop => prop.Addresses.Select(x => x.Features));
return person.FirstOrDefault();
}
}
We use EntityFramework 6.1 with CodeFirst in our web mvc application (StdWebApp). Now we want to make a new custom version of this application (CustomWebApp) .
The CustomWebApp will use most of the code of the standard one, in it's domain model it will extend the Person class.
In CustomDomain we make implement a new DbContext that must connect with the database of the custom app (CustomSqlDb).
In (C#) code there is no problem that there is a Person in Domain and in CustomDomain. However we have not been able to devise a mapping for Person in the Custom DbContext that will:
Create a single "Person" table.
Contains fields form "CustomDomain.Person" AND those from "Domain.Person".
We tried some variants like this:
modelBuilder.Entity<Person>().Map(m =>
{
m.MapInheritedProperties();
m.ToTable("Person");
}
);
using this document as our inspiration msdn mapping types
But EF complains about the simple name beeing equal.
Obviously we could rename the "Person" in "CustomDomain" to "PersonCustom" but that could lead to a lot of silly names if we have to do this again in the future like "PersonCustomExtraSpecial" etc.
Thoughts anyone?
UPDATE
we tried the solution suggested by mr100, here is the complete code:
namespace Domain
{
public class Person
{
public int Id { get; set; }
public string Stuff { get; set; }
}
}
namespace CustomDomain
{
public class Person : Domain.Person
{
public string ExtraStuff { get; set; }
}
}
namespace CustomDomain
{
public class DbModel : DbContext
{
DbSet<CustomDomain.Person> Persons { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<CustomDomain.Person>().Map(m => m.ToTable("Person"));
}
}
}
This still result in the error
The type 'CustomDomain.Person' and the type 'Domain.Person' both have the same simple name of 'Person' and so cannot be used in the same model. All types in a given model must have unique simple names. Use 'NotMappedAttribute' or call Ignore in the Code First fluent API to explicitly exclude a property or type from the model.
So we added the following code:
namespace CustomDomain
{
public class DbModel : DbContext
{
DbSet<CustomDomain.Person> Persons { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Ignore<Domain.Person>();
modelBuilder.Entity<CustomDomain.Person>().Map(m => m.ToTable("Person"));
}
}
}
Still same result.
To achieve this your DbContext class in CustomWebApps should have property People defined like this:
public DbSet<CustomDomain.Person> People {get; set;}
and no property:
public DbSet<Domain.Person> People {get; set;}
even if it comes from StdWebApp DbContext class from which CustomWebApp DbContext class may derive (if that is the case for you). Additionally you may set properly table name:
modelBuilder.Entity<Person>().ToTable("Person");
I already have a database with tables outside EF scope. But I want that the tables which will be used by EF to be created automatically.
public class SessionInfo
{
public Guid Id {get;set;}
public string Name { get; set; }
public DateTime StartsOn { get; set; }
public DateTime EndsOn { get; set; }
public string Notes { get; set; }
}
public class StudentsDbContext:DbContext
{
public StudentsDbContext():base("name=memory")
{
Database.Log = s => this.LogDebug(s);
}
public DbSet<SessionInfo> Sessions { get; set; }
}
This code just throws an exception because the table SessionInfoes doesn't exist.
using (var db = new StudentsDbContext())
{
db.Sessions.Add(new SessionInfo() {Id = Guid.NewGuid(), Name = "bla"});
var st = db.Sessions.FirstOrDefault();
}
What do I need to do so that EF will create the "SessionInfoes" (whatever name, it's not important) table by itself? I was under the impression that Ef will create the tables when the context is first used for a change or a query.
Update
After some digging, it seems that EF and Sqlite don't play very nice together i.e at most you can use EF to do queries but that's it. No table creation, no adding entities.
EF needs additional information in order to do this. You'll have to specify an IDatabaseInitializer first. Take a look at this list and find one that is appropriate for your needs (for example: MigrateDatabaseToLatestVersion, DropCreateDatabaseAlways, DropCreateDatabaseIfModelChanges, etc).
Then create your class:
public class MyDatabaseInitializer : MigrateDatabaseToLatestVersion
<MyDbContext,
MyDatabaseMigrationConfiguration>
Then also create the configuration for the initializer (ugh right?):
public class DatabaseMigrationsConfiguration
: DbMigrationsConfiguration<MyDbContext>
{
public DatabaseMigrationsConfiguration()
{
this.AutomaticMigrationDataLossAllowed = true;
this.AutomaticMigrationsEnabled = true;
}
protected override void Seed(MyDbContext context)
{
// Need data automagically added/update to the DB
// during initialization?
base.Seed(context);
}
}
Then one way to initialize the database is:
var myContext = new MyDbContext(/*connectionString*/);
Database.SetInitializer<MyDbContext>(new MyDatabaseInitializer());
myContext.Database.Initialize(true);
Some people prefer the to use the command line to migrate databases, but I don't want to assume I'll always have access to the database from a command lin.
Problem Summary: I have a Master and Detail entities. When I initialize a Master (myMaster), it creates an instance of Details (myMaster.Detail) and both appear to persist in the database when myMaster is added. However, when I reload the context and access myMasterReloaded.detail its properties are not initialized. However, if I pull the detail from the context directly, then this magically seems to initialize myMasterReloaded.detail. I've distilled this down with a minimal unit test example below. Is this a "feature" or am I missing some important conceptual detail?
//DECLARE CLASSES
public class Master
{
[Key, DatabaseGenerated(DatabaseGenerationOption.Identity)]
public Guid MasterId { get; set; }
public Detail Detail { get; set; }
public Master() { Detail = new Detail(); }
}
public class Detail
{
[Key, DatabaseGenerated(DatabaseGenerationOption.Identity)]
public Guid DetailId { get; set; }
public Master MyMaster{ get; set; }
}
public class MyDbContext : DbContext
{
public DbSet<Master> Masters { get; set; }
public DbSet<Detail> Details { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Master>()
.HasOptional(x => x.Detail)
.WithOptionalPrincipal(x => x.MyMaster)
.WillCascadeOnDelete(true);
}
}
//PERFORM UNIT TEST
[TestMethod]
public void UnitTestMethod()
{
//Start with fresh DB
var context = new MyDbContext();
context.Database.Delete();
context.Database.CreateIfNotExists();
//Create and save entities
var master = context.Masters.Create();
context.Masters.Add(master);
context.SaveChanges();
//Reload entity
var contextReloaded = new MyDbContext();
var masterReloaded = contextReloaded.Masters.First();
//This should NOT Pass but it does..
Assert.AreNotEqual(master.Detail.DetailId, masterReloaded.Detail.DetailId);
//Let's say 'hi' to the instance of details in the db without using it.
contextReloaded.Details.First();
//By simply referencing the instance above, THIS now passes, contracting the first Assert....WTF??
Assert.AreEqual(master.Detail.DetailId, masterReloaded.Detail.DetailId);
}
(This is the sticking point for a more sophisticated entity set. I've simply distilled this down to its simplest case I can't simply replace details with a complex type).
Cheers,
Rob
I think it's because when you first reload the Master, you have not eager-loaded the Detail, so the Detail entity will not be in the Entity Framework "graph" (internal memory). The only thing in the graph will be a single Master entity.
But when you query the Detail ("Let's say hi"), it is loaded into the graph and the reference was resolved based on the FK association, therefore your final test passes as the Master is now related to the Detail.
I could be wrong though - but that's what it sounds like.
Do you have lazy-loading enabled? If not, you need to eager-load the relationships you need.
Instead of this:
var masterReloaded = contextReloaded.Masters.First();
Try this:
var masterReloaded = contextReloaded.Masters.Include(x => x.Detail).First();
Matt Hamilton was right (See above). The problem was:
The Detail property should not be instantiated within the constructor, nor through the getters/setters via a backing member. If it's convenient to instantiate a Entity containing Properties in your new instance, then it may be helpful to have a separate initialize method which will not be automatically executed by the Entity Framework as it reconstructs objects from the database.
The Detail property needs to be declared virtual in the Master class for this to work properly.
The following WILL PASS (As expected/hope)
public class Master
{
[Key, DatabaseGenerated(DatabaseGenerationOption.Identity)]
public Guid MasterId { get; set; }
//Key new step: Detail MUST be declared VIRTUAL
public virtual Detail Detail { get; set; }
}
public class Detail
{
[Key, DatabaseGenerated(DatabaseGenerationOption.Identity)]
public Guid DetailId { get; set; }
//Set this to be VIRTUAL as well
public virtual Master MyMaster { get; set; }
}
public class MyDbContext : DbContext
{
public DbSet<Master> Masters { get; set; }
public DbSet<Detail> Details { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
//This sets up a BI-DIRECTIONAL relationship
modelBuilder.Entity<Master>()
.HasOptional(x => x.Detail)
.WithOptionalPrincipal(x => x.MyMaster)
.WillCascadeOnDelete(true);
}
}
[TestMethod]
public void UnitTestMethod()
{
var context = new MyDbContext();
context.Database.Delete();
context.Database.CreateIfNotExists();
//Create and save entities
var master = context.Masters.Create();
//Key new step: Detail must be instantiated and set OUTSIDE of the constructor
master.Detail = new Detail();
context.Masters.Add(master);
context.SaveChanges();
//Reload entity
var contextReloaded = new MyDbContext();
var masterReloaded = contextReloaded.Masters.First();
//This NOW Passes, as it should
Assert.AreEqual(master.Detail.DetailId, masterReloaded.Detail.DetailId);
//This line is NO LONGER necessary
contextReloaded.Details.First();
//This shows that there is no change from accessing the Detail from the context
Assert.AreEqual(master.Detail.DetailId, masterReloaded.Detail.DetailId);
}
Finally, it is also not necessary to have a bidirectional relationship. The reference to "MyMaster" can be safely removed from the Detail class and the following mapping can be used instead:
modelBuilder.Entity<Master>()
.HasOptional(x => x.Detail)
.WithMany()
.IsIndependent();
With the above, performing context.Details.Remove(master.Detail), resulted in master.Detail == null being true (as you would expect/hope).
I think some of the confusion emerged from the X-to-many mapping where you can initialize a virtual list of entities in the constructor (For instance, calling myDetails = new List(); ), because you are not instantiating the entities themselves.
Incidentally, in case anyone is having some difficulties with a one-to-many unidirectional map from Master to a LIST of Details, the following worked for me:
modelBuilder.Entity<Master>()
.HasMany(x => x.Details)
.WithMany()
.Map((x) =>
{
x.MapLeftKey(m => m.MasterId, "MasterId");
x.MapRightKey(d => d.DetailId, "DetailId");
});
Cheers, Rob