LINQ anonym object with result to delimited string (LINQ to Entities does not recognize the method 'System.String ToString()' method) - linq

Question

I am trying to get a ; demlimited string of all the relatives that a person has.
Four tables are involved:
USERTAB
PERSON
PERSON_RELATION
RELATION_TAB
Query
from u in USERTAB
select new
{
Person = from p in PERSON where p.USERID == u.USERID
select new
{
PNo = p.NO,
Name = p.NAME
Relatives = (from r in PERSON_RELATION where r.PSEQ == p.PSEQ select new
{
Description = (from rel in RELATION_TYPE where rel.TYPE_SEQ == r.TYPE_SEQ select rel.DESCRIPTION).ToArray() //(or also tried .ToString())
})
}
}
I'd like the Description field to be a ";" delimited list of all the relatives a user (person) has.
Using a ToString on my Relatives object it only fails runtime with. LINQ to Entities does not recognize the method 'System.String ToString()' method
Example: Description = "Father, Brother, Cousin"

Answer 1

You need to be clear about what parts of your query get translated to SQL to run on the server, and what parts run in your local application. The key is to construct a simple query to retrieve all the data, then use .AsEnumerable() to ensure that the remaining transformations don't get translated to SQL, and finally transform the data into a form useful for you. Something like
var query =
from u in USERTAB
select new
{
Person =
from p in PERSON
where p.USERID == u.USERID
select new
{
PNo = p.NO,
Name = p.NAME
Relatives =
from r in PERSON_RELATION
where r.PSEQ == p.PSEQ
select new
{
Description =
from rel in RELATION_TYPE
where rel.TYPE_SEQ == r.TYPE_SEQ
select pos.DESCRIPTION
}
}
}
};
var enumerable =
from u in query.AsEnumerable()
select new
{
Person =
from p in u.Person
select new
{
PNo = p.PNo,
Name = p.Name
Relatives =
string.Join(", ",
from r in p.Relatives
from d in r.Description
select d.Description)
}
}
};
should do the trick.

Answer 2

This should work: write an extension method for strings of array, like so:
public static ToCsv(this string[] strings)
{
return String.Join("," strings);
}
Then just tack .ToCsv() at the end of your .ToArray() call above, and it should do the trick!