fluent nhibernate hasmany relationship could not insert - nhibernate

Question

I have the following tables:
LANDLORD = Id (Primary Key), FirstName, Surname, EmailAddress, Title;
PROPERTY = Id (Primary Key), Type, NumberOfBedrooms, Address1, Address2, City, County, PostCode, LandlordId (Foreign Key to Landlord entity);
My Domain classes are:
public class Landlord:BaseEntity
{
public virtual string Title { get; set; }
public virtual string Surname { get; set; }
public virtual string FirstName { get; set; }
public virtual string EmailAddress { get; set; }
public virtual IList<Property> Properties { get; set; }
public Landlord()
{
Properties = new List<Property>();
}
}
public class Property:BaseEntity
{
public virtual string Type { get; set; }
public virtual int NumberOfBedrooms { get; set;}
public virtual string Address1 { get; set; }
public virtual string Address2 { get; set; }
public virtual string City { get; set; }
public virtual string County { get; set; }
public virtual string PostCode { get; set; }
public virtual Landlord Landlord { get; set; }
}
My Fluent NHibernate maps are:
public sealed class LandlordMap:ClassMap<Landlord>
{
public LandlordMap()
{
Id(x => x.Id).GeneratedBy.Identity();
Map(x => x.Title);
Map(x => x.Surname);
Map(x => x.FirstName);
Map(x => x.EmailAddress);
HasMany(x => x.Properties)
.KeyColumns.Add("LandlordId")
.Inverse()
.Cascade.All();
Table("LANDLORD");
}
}
public sealed class PropertyMap:ClassMap<Property>
{
public PropertyMap()
{
Id(x => x.Id).GeneratedBy.Identity();
Map(x => x.Type);
Map(x => x.NumberOfBedrooms);
Map(x => x.Address1);
Map(x => x.Address2);
Map(x => x.City);
Map(x => x.County);
Map(x => x.PostCode);
References(x => x.Landlord, "LandlordId");
Table("PROPERTY");
}
}
To test that a Landlord is saved to the database, I have the following code:
public class Program
{
static void Main(string[] args)
{
ILandlordRepository rep = new LandlordRepository();
//Create property object
Property p1 = new Property
{
Address1 = "123 LA Road",
Address2 = "Bilston",
City = "Harlem",
County = "West Mids",
NumberOfBedrooms = 2,
PostCode = "wv134wd",
Type = "Bungalow"
};
//Create landlord and assign property
var landlord = new Landlord();
landlord.Title = "Dr";
landlord.FirstName = "Rohit";
landlord.Surname = "Kumar";
landlord.EmailAddress = "rkhkp#p.com";
landlord.Properties.Add(p1);
//Add to the database
rep.SaveOrUpdate(landlord);
Console.ReadKey();
}
}
When I call SaveOrUpdate I get this error:
could not insert: [Homes4U.Service.DomainClasses.Property][SQL: INSERT INTO PROPERTY (Type, NumberOfBedrooms, Address1, Address2, City, County, PostCode, LandlordId) VALUES (?, ?, ?, ?, ?, ?, ?, ?); select SCOPE_IDENTITY()]
Does anybody now why this is happening?

Answer 1

In your mappings, you've specified that the Property object is responsible for saving its reference to Landlord.
HasMany(x => x.Properties)
.KeyColumns.Add("LandlordId")
// Inverse means that the other side of the
// relationship is responsible for creating the reference
.Inverse()
.Cascade.All();
When you attempt to save the object, the Property object in the Properties collection has no reference to the landlord it belongs to. Under the hood, it'll attempt to insert a NULL into the LandlordId column.
This is why you are getting your error.
EDIT
To resolve, save the landlord first, without a reference to any property.
ILandlordRepository rep = new LandlordRepository();
IPropertyRepository pro = new PropertyRepository();
//Create landlord
var landlord = new Landlord();
landlord.Title = "Dr";
landlord.FirstName = "Rohit";
landlord.Surname = "Kumar";
landlord.EmailAddress = "rkhkp#p.com";
rep.SaveOrUpdate(landlord);
// Now add the landlord reference to the property and
// save
/Create property object
Property p1 = new Property
{
Address1 = "123 LA Road",
Address2 = "Bilston",
City = "Harlem",
County = "West Mids",
NumberOfBedrooms = 2,
PostCode = "wv134wd",
Type = "Bungalow",
Landlord = landlord
};
pro.SaveOrUpdate(p1);
You may need to reload the Landlord after saving it.
EDIT 2
See this question on Inverse.
Inverse Attribute in NHibernate