Linq To Entities 5 re-use Expression in another entity

Linq To Entities 5 re-use Expression in another entity

I've been trying to find this, but I've not had luck. Say I have a
database with 2 tables, person and address.
table person
id int
name varchar(50)
addressId int
table address
id int
street varchar(50)
country varchar(50)
In my data layer, I have a business object for Address, which is exposed
to external callers. I found an expression that I could use to centralize
my creation code at the SQL level. This way I don't have to write:
db.Address.Select( x => new Biz.Address{ street = x.street} ).ToList();
//and all the other properties etc
everywhere. Instead I can now do:
db.Address.Select(AddressDto.ToDto).ToList();
Using this code:
internal static class AddressDto
{
internal static readonly Expression<Func<Address, Biz.Address>> ToDto =
src => new Biz.Address
{
Id = src.id,
Street = src.street,
Country = src.country
};
}
The problem is now that I am trying to do the same thing for the Person
object, and I want to re-use this method to fill in the address. However I
can't seem to utilize an expression in it.
class Person
{
int Id;
string Name;
Address address;
}
internal static class PersonDto
{
internal static readonly Expression<Func<Person, Biz.Person>> ToDto =
src => new Biz.Person
{
Id = src.id,
Name = src.name,
address = src.Address //How do i set this to an
expression?
};
}
The reason I ask for the expression, is because while it compiles fine if
I use a normal method, it blows up at runtime, because it can't translate
that to the object store. However, if I do:
address = AddressDto.ToDto(src.Address)
the compiler rejects that, as it wants a method, delegate, or event. I'd
love to find a way to do this. the idea I'm trying to implement is to
basically centralize the code that maps the Entity to the business object,
so that my other code is kept clean and maintenance is easier when the
schema changes. If there is a different method signature I have to create
and maintain, that'd be fine, as I'd place it in the same file and live
with it. I just can't seem to find the magic combination that'll make this
work.
Thanks!