How do I handle nested NPoco objects that may be null?

Question

I am using NPoco for object mapping from my database. I have the following entities:

public abstract class NamedEntity
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Person : NamedEntity
{
    public Office Office { get; set; }
}

public class Office : NamedEntity
{
    public Address Address { get; set; }
    public Organisation ParentOrganisation { get; set; }
}

public class Address
{
     public string AddressLine1 { get; set; }
}

public class Organisation : NamedEntity
{
}

and I am retrieving the objects using NPoco in my repository:

var people = Context.Fetch<Person, Office, Address, Organisation>(sql);

This is working fine, except for the case where a Person does not have an Office, in which case result of the LEFT JOIN in the sql query returns null for the Office, Address and Organisation columns.

In this situation, an unhandled exception is thrown in NPoco:

System.Reflection.TargetInvocationException: 
Exception has been thrown by the target of an invocation. 
---> System.NullReferenceException: 
Object reference not set to an instance of an object.
at poco_automapper(Person , Office , Address , Organisation )
--- End of inner exception stack trace ---
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at NPoco.MultiPocoFactory.CallCallback[TRet](Delegate callback, IDataReader dr, Int32 count)
at NPoco.MultiPocoFactory.<>c__DisplayClassa`1.<CreateMultiPocoFactory>b__9(IDataReader reader, Delegate arg3)
at NPoco.Database.<Query>d__14`1.MoveNext()

Is there a way to handle this situation? Or will I have to resort to a flattened object, or separate database calls?

Answer 1

This has been fixed in NPoco 2.2.40.
Thanks for reporting it.

Answer 2

Try creating a constructor to initialize objects:

public abstract class NamedEntity
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Person : NamedEntity
{
    public Person()
    {
        Office = new Office();
    }
    public Office Office { get; set; }
}

public class Office : NamedEntity
{
    public Office()
    {
        Address = new Address();
        ParentOrganisation = new Organisation();
    }
    public Address Address { get; set; }
    public Organisation ParentOrganisation { get; set; }
}

public class Address
{
    public string AddressLine1 { get; set; }
}

public class Organisation : NamedEntity
{
}