Develop Reference

How to get a list of children in a self-referencing table (Parent-Child) using EF Core?

I use the following Model to create a self-referencing table:
public class Part
{
[Key]
public long PartId { get; set; }
[Required]
public string PartName { get; set; }
public long? ParentPartId { get; set; }
public Part Parentpart { get; set; }
//Navigation properties
public ICollection<Part> ChildParts { get; set; } //For self-referencing
}
The Fluent API is:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
//For parts self-referencing
modelBuilder.Entity<Part>(entity =>
{
entity.HasKey(x => x.PartId);
entity.Property(x => x.PartName);
entity.HasOne(e => e.Parentpart)
.WithMany(e => e.ChildParts)
.HasForeignKey(e => e.ParentPartId)
.IsRequired(false)
.OnDelete(DeleteBehavior.Restrict);
});
}
I can use the following code to get all the parents of a given part:
[HttpGet]
public async Task<IActionResult> GetParentPartsList(string partName)
{
var q = _sqlServerContext.Parts.Where(x => x.PartName == partName).Include(x => x.Parentpart);
while (q.Select(x => x.ParentPartId) == null)
{
q = q.ThenInclude(x => x.Parentpart);
}
q = q.ThenInclude(x => x.Parentpart);
return Ok(await q.ToListAsync());
}
I want to get a list of all children for a given part. I searched some threads such as this link, but they have a one-one relationship between child and parent while I need a one-many relationship. How can I achieve this?

How to define a domain model where the Primary Key is also the Foreign Key with fluent api

My problem is similar to Is it possible to have a relation where the foreign key is also the primary key? but I have to do this with Fluent API.
I have basically the same situation as described in the question, but I cannot use annotations on my domain models due to our coding standards. Here is a bit of code (Clarified):
Domain Classes:
public class Table1
{
public long ID { get; set; }
public int SubTableType { get; set; }
...
public Table2 Table2 { get; set; }
public Table3 Table3 { get; set; }
public List<Table4> Table4s { get; set; }
public List<Table5> Table5s { get; set; }
}
public class Table2
{
public long ID { get; set; }
public string Location { get; set; }
public string Task { get; set; }
...
public Table1 Table1 { get; set; }
public Table6 Table6 { get; set; }
public List<Table7> Table7s { get; set; }
}
public class Table3
{
public long ID { get; set; }
public string DescriptionAndLocation { get; set; }
...
public Table1 Table1 { get; set; }
}
Configuration Classes:
internal class Table1Configuration : EntityTypeConfiguration<Table1>
{
public Table1Configuration()
{
ToTable("Table1");
HasKey(so => so.ID);
Property(so => so.SubTableType)
.IsRequired();
Property(so => so.ID)
.IsRequired()
.HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity);
...
}
}
internal class Table2Configuration : EntityTypeConfiguration<Table2>
{
public Table2Configuration()
{
ToTable("Table2");
HasKey(bc => bc.ID);
Property(bc => bc.ID)
.IsRequired();
Property(bc => bc.Location)
.IsOptional()
.HasColumnType("nvarchar")
.HasMaxLength(50);
Property(bc => bc.Task)
.IsOptional()
.HasColumnType("nvarchar")
.HasMaxLength(4000);
...
HasRequired(bc => bc.Table1)
.WithOptional(so => so.Table2);
HasRequired(bc => bc.Table8)
.WithMany(bot => bot.Table2s)
.HasForeignKey(bc => bc.Tabe8ID);
}
}
internal class Table3Configuration : EntityTypeConfiguration<Table3>
{
public Table3Configuration()
{
ToTable("Table3");
HasKey(hic => hic.ID);
Property(hic => hic.DescriptionAndLocation)
.IsOptional()
.HasColumnType("nvarchar")
.HasMaxLength(4000);
Property(hic => hic.ID)
.IsRequired()
.HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity);
HasRequired(hic => hic.Table1)
.WithOptional(so => so.Table3);
}
}
When I run this code I get the error:
Invalid column name 'Table2_ID'.

What you are asking is the so called Shared Primary Key Associations, which is the standard (and better supported) EF6 model for one-to-one relationships.
Rather than removing the ID property, you should remove the MapKey call which is used to define a shadow FK property (which you don't need).
Since the property called ID by convention is a PK and required, basically all you need is this:
HasRequired(hic => hic.Table1)
.WithOptional(so => so.Table2); // or Table3
or the explicit equivalent of [Key] / [ForeignKey] combination:
HasKey(hic => hic.ID);
HasRequired(hic => hic.Table1)
.WithOptional(so => so.Table2); // or Table3
Exactly as the example for Configuring a Required-to-Optional Relationship (One-to–Zero-or-One) from the documentation.

I would try something like this:
modelBuilder.Entity<Table1>().HasKey(t => t.ID);
modelBuilder.Entity<Table1>().Property(t =>t.ID)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
modelBuilder.Entity<Table1>()
.HasOptional(t1 => t1.Table2)
.WithRequired(t2 => t2.Table1).Map(m => m.MapKey("ID"));

Fluent NHibernate "Could not resolve property"

I have read a lot of the questions about that same error but none since to match my exact problem. I'm trying to access the property of an object, itself part of a root object, using Fluent NHibernate. Some answers say I need to use projections, others that I need to use join, and I think it should work through lazy loading.
Here are my two classes along with the Fluent mappings:
Artist class
public class Artist
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual IList<Album> Albums { get; set; }
public virtual string MusicBrainzId { get; set; }
public virtual string TheAudioDbId { get; set; }
public Artist() { }
}
public class ArtistMap : ClassMap<Artist>
{
public ArtistMap()
{
LazyLoad();
Id(a => a.Id);
Map(a => a.Name).Index("Name");
HasMany(a => a.Albums)
.Cascade.All();
Map(a => a.MusicBrainzId);
Map(a => a.TheAudioDbId);
}
}
Album class
public class Album
{
public virtual int Id { get; set; }
public virtual Artist Artist { get; set; }
public virtual string Name { get; set; }
public virtual IList<Track> Tracks { get; set; }
public virtual DateTime ReleaseDate { get; set; }
public virtual string TheAudioDbId { get; set; }
public virtual string MusicBrainzId { get; set; }
public Album() { }
}
public class AlbumMap : ClassMap<Album>
{
public AlbumMap()
{
LazyLoad();
Id(a => a.Id);
References(a => a.Artist)
.Cascade.All();
Map(a => a.Name).Index("Name");
HasMany(a => a.Tracks)
.Cascade.All();
Map(a => a.ReleaseDate);
Map(a => a.TheAudioDbId);
Map(a => a.MusicBrainzId);
}
}
And the error happens when this code is interpreted:
var riAlbum = session.QueryOver<Album>()
.Where(x => x.Name == albumName && x.Artist.Name == artist)
.List().FirstOrDefault();
The error happens when Fluent NHibernate tries to resolve the x.Artist.Name value:
{"could not resolve property: Artist.Name of: Album"}
What would be the correct way of doing this?

You have to think of your QueryOver query as (nearly) directly translating into SQL. With this in mind, imagine this SQL query:
select
Album.*
from
Album
where
Album.Name = 'SomeAlbumName' and
Album.Artist.Name = 'SomeArtistName'
This won't work because you can't access a related table's properties like that in a SQL statement. You need to create a join from Album to Artist and then use a Where clause:
var riAlbum =
session.QueryOver<Album>()
.Where(al => al.Name == albumName)
.JoinQueryOver(al => al.Artist)
.Where(ar => ar.Name == artistName)
.List()
.FirstOrDefault();
Also, since you're using FirstOrDefault, you may want to consider moving that logic to the database end. Currently, you're pulling back every record matching your criteria and then taking the first one. You could use .Take to limit the query to 1 result:
var riAlbum =
session.QueryOver<Album>()
.Where(al => al.Name == albumName)
.JoinQueryOver(al => al.Artist)
.Where(ar => ar.Name == artistName)
.Take(1)
.SingleOrDefault<Album>();

Another explanation is that you are missing your mapping of this property or field in a NHibernateClassMapping definition. I came here about why I was getting this error based on the following scenario.
var query = scheduleRepository.CurrentSession().Query<Schedule>()
.Where(x => x.ScheduleInfo.StartDate.Date < dateOfRun.Date);
This was giving me a Could Not Resolve Property error for StartDate. This was a head scratcher, since I use this syntax all the time.
My mapping file was the following:
public class ScheduleInfoMapping : NHibernateClassMapping<ScheduleInfo>
{
public ScheduleInfoMapping()
{
DiscriminateSubClassesOnColumn("Type");
Map(x => x.Detail).MapAsLongText();
}
}
which was missing the StartDate. Changed to:
public class ScheduleInfoMapping : NHibernateClassMapping<ScheduleInfo>
{
public ScheduleInfoMapping()
{
DiscriminateSubClassesOnColumn("Type");
Map(x => x.Detail).MapAsLongText();
Map(x => x.StartDate);
}
}
Which resolved the error.

Mapping Data Entity with Self-Navigating Property to Business Entity

I'm having a lot of trouble with creating my business entities from my data entities.
Github
My Data.Entities.User looks as follows:
public class User
{
public User()
{
Messages = new List<Message>();
Followers = new List<User>();
Favorites = new List<Message>();
Notifications = new List<Notification>();
SubscribedTopics = new List<Topic>();
}
public string Id { get; set; }
public string Name { get; set; }
public string Email { get; set; }
public string Tag { get; set; }
public string Picture { get; set; }
public ICollection<Message> Messages { get; set; }
public ICollection<User> Followers { get; set; }
public ICollection<Message> Favorites { get; set; }
public ICollection<Notification> Notifications { get; set; }
public ICollection<Topic> SubscribedTopics { get; set; }
}
My Data.Mappers.UserMapper looks like this:
class UserMapper : EntityTypeConfiguration<User>
{
public UserMapper()
{
// Table Mapping
ToTable("Users");
// Primary Key
HasKey(u => u.Id);
Property(u => u.Id)
.IsRequired();
// Properties
Property(u => u.Name)
.IsRequired()
.HasMaxLength(140);
Property(u => u.Email)
.IsRequired()
.HasMaxLength(255)
.IsUnicode(false);
Property(u => u.Tag)
.IsRequired()
.IsUnicode(false)
.HasMaxLength(255)
.HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute()));
Property(u => u.Picture)
.IsOptional();
// Relationships
HasMany(u => u.Followers)
.WithMany()
.Map(u => u.MapLeftKey("FollowerID"));
HasMany(u => u.Favorites)
.WithMany()
.Map(u => u.MapLeftKey("MessageID"));
HasMany(u => u.SubscribedTopics)
.WithMany(t => t.Subscribers)
.Map(u =>
{
u.ToTable("TopicSubscribers");
u.MapLeftKey("UserID");
u.MapRightKey("TopicID");
});
}
}
Finally, my Domain.Entities.User like this:
public class User : EntityBase<string>
{
public string Name { get; set; }
public string Email { get; set; }
public string Tag { get; set; }
public string Picture { get; set; }
public IEnumerable<Message> Messages { get; set; }
public IEnumerable<User> Followers { get; set; }
public IEnumerable<Message> Favorites { get; set; }
public IEnumerable<Notification> Notifications { get; set; }
public IEnumerable<Topic> SubscribedTopics { get; set; }
protected override void Validate()
{
if (string.IsNullOrWhiteSpace(Name))
{
AddBrokenRule(new ValidationRule("Name", "Name_Missing"));
}
if (string.IsNullOrWhiteSpace(Email))
{
AddBrokenRule(new ValidationRule("Email", "Email_Missing"));
}
if (string.IsNullOrWhiteSpace(Tag))
{
AddBrokenRule(new ValidationRule("Tag", "Tag_Missing"));
}
System.Uri uriResult;
if (!string.IsNullOrWhiteSpace(Picture) &&
Uri.TryCreate(Picture, UriKind.Absolute, out uriResult) &&
(uriResult.Scheme == Uri.UriSchemeHttp || uriResult.Scheme == Uri.UriSchemeHttps))
{
AddBrokenRule(new ValidationRule("Picture", "Picture_InvalidURI"));
}
}
}
EntityBase adds the Id parameter, so as far as parameters are concerned, these two classes should be identical.
The part where I run into trouble is mapping the Data Entity to the Domain Entity.
public override IEnumerable<User> GetAll()
{
IEnumerable<User> user = _context.Users.Project()
.To<User>("Followers");
return user;
}
I think what's causing trouble is the circular navigational properties. User1 might have a follower named User2, while at the same time following User2.
So far I have tried both AutoMapper and ValueInjecter, but I have not had any success with either.
I tried adding "Virtual" to all navigational properties, enabling lazy and proxy loading, but this causes both AutoMapper and ValueInjecter to fail. ValueInjecter due to a already opened datareader and AutoMapper because of a type mismatch.
I tried explicitly loading navigational properties, but as soon as I Include("Followers") on User, I get a stackoverflow.
Trying to create a AutoMapperConfiguration where I specify a maxDepth of 1 yields a stackoverflow unless I add opt.ExplicitExpansion to every navigational property.
If i then try to explicitly expand a navigational property, I get
The type 'ShortStuff.Domain.Entities.User' appears in two structurally
incompatible initializations within a single LINQ to Entities query. A
type can be initialized in two places in the same query, but only if
the same properties are set in both places and those properties are
set in the same order.
Ideally I would want a solution that lets me explicitly control which navigational properties to expand without recursing.
For example, I'd like to do something like:
_context.Users.Include("Followers").NoNavigation().AsEnumerable();
And then I would be able to access User.Followers and have a list of other users, with their navigational properties set to null.
Many thanks!
Full source code of my Repository / Service learning project can be found on Github at https://github.com/Bio2hazard/ShortStuff/tree/master/ShortStuffApi
Edit:
I made some progress.
I got things to work by turning off proxy generation & lazy loading, and then using ValueInjector like so:
IEnumerable<Data.Entities.User> userList = _context.Users.Include("Followers").Include("Favorites").Include("Messages").Include("Notifications").Include("SubscribedTopics");
IEnumerable<User> users = userList.Select(u => new User
{
Id = u.Id,
Email = u.Email,
Picture = u.Picture,
Tag = u.Tag,
Name = u.Name,
Followers = u.Followers.Select(uu => new User().InjectFrom<SmartConventionInjection>(uu)).Cast<User>(),
Favorites = u.Favorites.Select(uf => new Message().InjectFrom<SmartConventionInjection>(uf)).Cast<Message>(),
Messages = u.Messages.Select(um => new Message().InjectFrom<SmartConventionInjection>(um)).Cast<Message>(),
Notifications = u.Notifications.Select(un => new Notification().InjectFrom<SmartConventionInjection>(un)).Cast<Notification>(),
SubscribedTopics = u.SubscribedTopics.Select(ut => new Topic().InjectFrom<SmartConventionInjection>(ut)).Cast<Topic>()
});
But that's a ton of code. I could probably create a factory for this, but there has got to be a easier way, right?

with ValueInjecter you can use the SmartConventionInjection which will only access the properties if it needs to get the value:
http://valueinjecter.codeplex.com/wikipage?title=SmartConventionInjection&referringTitle=Home
other injections usually get the value too so that you could use it in the matching algorithm
for an example of using valueinjecter with Entity Framework (code first, latest)
have a look at this project: http://prodinner.codeplex.com

Many to Many mapping not working - EF 4.1 RC

UPDATE: After a bit more research it seems a number of my many-to-many mappings aren't working. Hmmm...
I'm upgrading a data access project from EF 4.1 CTP4 to EF 4.1 RC and I'm having trouble with the new EntityTypeConfiguration<T> setup.
Specifically I'm having an issue with a Many-to-Many relationship. I'm getting a Sequence contains no elements exception when I'm trying to get the .First() item.
The particular exception isn't really that interesting. All it's saying is that there are no items BUT I know there should be items in the collection - so there must be an issue with my new mappings.
Here's the code I have so far:
Product Model
public class Product : DbTable
{
//Blah
public virtual ICollection<Tag> Categories { get; set; }
public Product()
{
//Blah
Categories = new List<Tag>();
}
}
BaseConfiguration
public class BaseConfiguration<T> : EntityTypeConfiguration<T> where T : DbTable
{
public BaseConfiguration()
{
this.HasKey(x => x.Id);
this.Property(x => x.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
this.Property(x => x.UpdatedOn);
this.Property(x => x.CreatedOn);
}
}
ProductConfiguration
public class ProductConfiguration : BaseConfiguration<Product>
{
public ProductConfiguration()
{
this.ToTable("Product");
//Blah
this.HasMany(x => x.Categories)
.WithMany()
.Map(m =>
{
m.MapLeftKey("Tag_Id");
m.MapRightKey("Product_Id");
m.ToTable("ProductCategory");
});
}
}
Previous CTP4 Mapping the worked!
this.HasMany(x => x.Categories)
.WithMany()
.Map("ProductCategory", (p, c) => new { Product_Id = p.Id, Tag_Id = c.Id });
Can anyone see anything that needs fixing? Let me know if you want me to provide more code.
EDIT: More Code
DbTable
public class DbTable : IDbTable
{
public int Id { get; set; }
public DateTime UpdatedOn { get; set; }
public DateTime CreatedOn { get; set; }
}
Tag
public class Tag
{
public int Id { get; set; }
public string Name { get; set; }
public string Slug { get; set; }
public bool Visible { get; set; }
public virtual TagType TagType { get; set; }
}
TagConfiguration
public class TagConfiguration : EntityTypeConfiguration<Tag>
{
public TagConfiguration()
{
this.ToTable("Tags");
this.HasKey(x => x.Id);
this.Property(x => x.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity).HasColumnName("tag_id");
this.Property(x => x.Name).HasMaxLength(300).HasColumnName("tag_name");
this.Property(x => x.Slug).HasMaxLength(500).HasColumnName("tag_slug");
this.Property(x => x.Visible).HasColumnName("tag_visible");
this.HasRequired(x => x.TagType).WithMany(tt => tt.Tags).Map(m => m.MapKey("tagtype_id"));
}
}
Yes, this is a legacy database with naming conventions up to boohai.
I know the Tag class must be wired up correctly because Product has another property Specialization which is also mapped to Tag and it loads correctly. But do note that it's mapped in a one-to-many manner. So it seems to be the many-to-many with Tag.
I'll start checking out if any many-to-many associations are working.

You need to specify both navigation properties to do many to many mapping.
Try adding the lambda in the WithMany property pointing back to the products:
this.HasMany(x => x.Categories)
.WithMany(category=>category.Products)
.Map(m =>
{
m.MapLeftKey(t => t.TagId, "Tag_Id");
m.MapRightKey(t => t.ProductId, "Product_Id");
m.ToTable("ProductCategory");
});
(crossing fingers...)

I haven't used the Code-First approach yet, but when working with POCOs I had to enable Lazy-Loading, to make Navigation Properties work. This is of course by design, but I don't know if you have to explicitly enable this behavior for Code-First.