Related Entity Query - code-first

Question

I have a database with thee tables - Organisations, Locations and OrganisationLocations for example. Organisations holds information on companies, Locations holds information on offices address, and OrganisationLocations holds the many-to-many relationship info about the companies and their addresses. For example Company A might be locations X and Y, Company B might be in locations Y and Z.
These are the generated classes
public partial class Locations
{
public Locations()
{
OrganisationLocations = new HashSet<OrganisationLocations>();
}
public long Id { get; set; }
public string Description { get; set; }
public string City { get; set; }
public string Street { get; set; }
public string PostCode { get; set; }
public string Name { get; set; }
public virtual ICollection<OrganisationLocations> OrganisationLocations { get; set; }
}
public partial class Organisations
{
public Organisations()
{
OrganisationLocations = new HashSet<OrganisationLocations>();
}
public long Id { get; set; }
public string Name { get; set; }
public string Owner { get; set; }
public string ContactName { get; set; }
public string Email { get; set; }
public string Telephone { get; set; }
public virtual ICollection<OrganisationLocations> OrganisationLocations { get; set; }
}
public partial class OrganisationLocations
{
public long Id { get; set; }
public long OrganisationId { get; set; }
public long LocationId { get; set; }
public virtual Locations Location { get; set; }
public virtual Organisations Organisation { get; set; }
}
The DB Context looks like this:
public class PfApiContext : DbContext
{
public PfApiContext(DbContextOptions<PaymentAPIContext> options)
: base(options)
{
}
public DbSet<Locations> Locations { get; set; }
public DbSet<Organisations> Organisations { get; set; }
public virtual DbSet<OrganisationLocations> OrganisationLocations { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<OrganisationLocations>(entity =>
{
entity.HasOne(d => d.Location)
.WithMany(p => p.OrganisationLocations)
.HasForeignKey(d => d.LocationId)
.OnDelete(DeleteBehavior.ClientSetNull)
.HasConstraintName("FK_84m7dbl1gv1p6tg1wquwm8j5u");
entity.HasOne(d => d.Organisation)
.WithMany(p => p.OrganisationLocations)
.HasForeignKey(d => d.OrganisationId)
.OnDelete(DeleteBehavior.ClientSetNull)
.HasConstraintName("FK_r0mkkndb6c2tr9nl0rgjm068t");
});
}
}
How would I get, for example, all the company data for all the companies in Location X? At the point I'm querying this I actually know the LocationID, so the SQL would be
SELECT * FROM [dbo].[Organisations] WHERE Id IN (SELECT [OrganisationId] FROM [dbo].[OrganisationLocations] WHERE [LocationId] = 1)
This is probably really simple and I'm just being stupid, but I'm new to EFCore and LINQ, and the syntax of this has me scratching my head.
Selecting locations based on a location name I can understand
var locationUsers = await _pfApiContext.UserLocations.Where
(o => o.LocationName == locationName).ToListAsync();
but this is confusing me something terrible.
Thanks for any help

Answer 1

I would remove the virtual collections and objects from all three classes and then remove the Id field (assuming it's the primary key) in the OrganisationLocations table. The OrganisationId and the LocationId fields in the OrganisationLocations should be both the primary keys and the foreign keys in order to make it a many-to-many relationship between OrganisationLocations, Locations, and Organisation. Then you can use Linq to do a simple join query to get the info you're looking for. For example:
var orgs = (from ol in PfApiContext.OrganisationLocations
inner join o in PfApiContext.Organisation on o.Id equals ol.OrganisationId
inner join l in PfApiContext.Locations on ol.LocationId equals l.Id
where ol.LocationId = 1
select new Organisation()
{
Id = o.Id,
Name = o.Name,
Owner = o.Ower,
etc...
}