I'm developing a plugin application with EF6, code first.
I have one main context with an entity called User
:
public class MainDataContext : DbContext
{
public MainDataContext(): base("MainDataContextCS") {}
public DbSet<User> Users { get; set; }
}
And then another context for PluginX, on another project which references the base one:
public class PluginDataContext : DbContext
{
public PluginDataContext () : base("MainDataContextCS") {
}
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
modelBuilder.HasDefaultSchema("PluginX");
base.OnModelCreating(modelBuilder);
}
public DbSet<Booking> Bookings { get; set; }
}
And this neatly creates, on the same Database (same connection string), the PluginX.Bookings
Table.
The problem here is that the Booking
entity contains a reference to User
entity:
public class Booking
{
public int Id { get; set;}
public virtual User CreationUser { get; set;}
public BookingStatus Status { get; set; }
}
And when running Add-Migration
for the plugin context EF will try to create another User
entity called PluginX.User
.
How can this be solved? Is there a way to share a common entity, in another DbContext
?
When you work with multiple contexts you have two options:
When you add the Booking entity, don't use the DbSet.Add()
method. Instead use the DbSet.Attach()
method and set the DbContext.Entry(Entity).State
property for the Booking to EntityState.Added
and make sure the DbContext.Entry(Entity).State
for User stays EntityState.Unchanged
.
So for example instead of doing this:
pluginDataContext.dbBooking.Add(myNewBooking);
Do this:
pluginDataContext.dbBooking.Attach(myNewBooking);
pluginDataContext.Entry(myNewBooking).State = EntityState.Added;
This is because the Add()
method marks all entities in the object graph as EntityState.Added
which will cause inserts without checking if the entity already exists in the database. The Attach()
method simply makes the context begin tracking the entity.
This is why I almost never use DbSet.Add()
.