I am involved in a project where we map already existing C# code to database using Entity Framework Code First. I am not going to reproduce the code itself here, but I will present some pseudo-code that should cover the same issue.
I am trying to map a class to the database that has lists of other classes. I will show you an example:
public Class ListClass
{
public List<SubClassA> ListOne
{
get { return BaseClass.OfType<SubClassA>().Where(b => !b.BoolOne && b.BoolTwo).ToList(); }
}
public List<SubClassA> ListTwo
{
get { return BaseClass.OfType<SubClassA>().Where(b => b.BoolOne && b.BoolTwo).ToList(); }
}
}
public abstract class BaseClass
{
public bool BoolOne {get; set;}
#Region EF
public GUID PrimaryKey {get; set;}
public GUID ListClassForeignKey {get; set;}
#EndRegion
}
public class SubClassA : BaseClass
{
public bool BoolTwo {get; set}
}
Class SubClassB : BaseClass
{
//Contents..
}
Summary: ListClass contains lists of SubClassA. The BaseClass and SubClassA does not know anything about the ListClass. The GUID-attributes in BaseClass is added for use with Entity Framework, otherwise no existing classes have been changed. That is why we use Fluent API for this project:
class ListClassConfiguration : EntityTypeConfiguration<ListClass>
{
public ListClassConfiguration()
{
HasKey(f => f.PrimaryKey);
Property(f => f.PrimaryKey).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
HasMany(f => f.ListOne).WithOptional().HasForeignKey(f => f.ListClassForeignKey);
HasMany(f => f.ListTwo).WithOptional().HasForeignKey(f => f.ListClassForeignKey);
}
}
In the Context-class we simply add this configuration. The database is deleted whenever the model is changed. I am currently using TPH-mapping for the BaseClass and it's sub-classes.
When I try to add and save the ListClass with the refered objects in the list, I get this exception:
InvalidOperationException. The foreign key component 'ListClassForeignKey' is not a declared property on type 'SubClassA'. Verify that it has not been explicitly excluded from the model and that it is a valid primitive property.
So, any advice?
Edit: I've noticed that in the real project, there seem to be empty lists. I tried to remove the foreignkey in the configuration-class, and I got a databasetable with no contents (one row with only NULL-values in the columns). In this example, that would mean that the TPH-table with the name 'BaseClass' only is empty / has only NULL-values. Could that explain some of the problem?
