How to include parent objects list in child entity object - silverlight

Question

I have the following tables in my database
Table1: tblAddressType (Id, Name)
Table2: tblAddressDtls (Id, AddressTypeId, Address1)
I am left joining the above two tables to get list of all address types and corresponding address details as follows
SQL Query:
select t1.*, t2.*
from tblAddressType t1
left outer join tblAddressDtls t2 on t1.Id = t2.AddressTypeId and t2.Id = 1;
For the above tables, i have created POCO entity classes as follows:
[Table("tblAddressType ")]
public partial class AddressType
{
[Key]
[Column(Name="ID")]
public int ID { get; set; }
[Required]
[Column(Name = "Name")]
public virtual string Name {get; set;}
[Include]
[Association("AddressTypeAddress", "ID", "AddressTypeId")]
public virtual ICollection<Address> Addresses { get; set; }
}
[Table("tblAddress", SchemaName="dbo")]
public class Address
{
[Column(Name="ID")]
public int ID { get; set; }
[Column(Name = "AddressTypeId")]
public int? AddressTypeId{ get; set; }
[Column(Name = "Address1")]
public string Address1{ get; set; }
[Include]
[Association("AddressTypeAddress", "AddressTypeId", "ID", IsForeignKey = true)]
public virtual AddressType AddressType { get; set; }
}
and, to fetch the data as shown in the sql query above, i have written the following LINQ query in my service code and this query returns me the data as needed:
var qry = (from p in dbContext.AddressTypes
join pa in (from t in dbContext.Addresses
where t.ID == 1 select t)
on p.ID equals pa.AddressTypeId into ppa
from t in ppa.DefaultIfEmpty()
select t).AsQueryable();
Now, I want to write a domain service method named "GetAddressById(int addressId)" which should return me the matching Address object along with list of AddressType objects as i need to bind list of "AddressType" objects to the drop down box in Add/Edit address screen.
I wanted to include and fetch list of "AddressType" objects data at the time of
fetching Address object data itself to avoid round-trip to server
in my silverlight client app.
Kindly suggest me the best possible way to achieve this functionality?

Answer 1

NEW:
I assume that in the database, Addresses has a relation to AddressTypes and again that you are using EntityFramework.
GetAddressById(int addressId){
return dbContext.Address.SingleOrDefault(a => a.ID == addressId).Include("AddressTypes");
}
that row of code would now get a single address which has the id of addressId, if there are none it would return null or if more returned it would throw an exception, the Include would tell EF that you also want AddressTypes to be loaded when you get the address and would create an appropriate join to make this happen, all this would make into a single query to the database and get the result that you want.
OLD:
Let's say we want the AddressType and all its Addresses with just one call to the db (asuming you use EntityFramework), we would call a method like
GetAddressTypeIncludingAddresses(int id){
return _context.AddressType.Include("Addressess");
/*if you use ctp5 of ef code first you should even be able to do (at => at.Addresses) in the include */
}
and then when you have it just do addressType.Id and foreach(var address in addressType.Addresses){} and the like when you use it.
I hope I understood your question, if not try again and I'll edit my answer.

Answer 2

You could do this by creating a stored proc in your database that returns mutliple result sets. First the one which gets you your desired child and parent and second the one that gets you your list of parents. Then you can use the work-around described here:
http://blogs.msdn.com/b/swiss_dpe_team/archive/2008/02/04/linq-to-sql-returning-multiple-result-sets.aspx
Which allows you to get each part of the results.
As an aside, you don't need a left join for your query. Since your where clause references the table on the right you will never get null values on the right side of the join. Use an inner join instead.