Linq2EF: Concat all values in another table into a string

Question

Let's say I have two entities:

Physician
Credentials

And a physician can have many credentials, such as Dr. Jones can have MD, DO, MPH as credentials. So I need to generate a report via Linq that concatenates the credentials into a single string. For example:

from p in Physicians
select
{
   p.Name
   p.Credentials (??? <- concatenated list of all credentials ?????)
}

I have played with "p.Credentials.Aggregate((a,b) => a.Abrev + ',' + b.Abrev)" to no avail, but I'm not sure I have the syntax correct.

Answer 1

Uhm.... I've not tested it, but you can try:

from p in Physicians
select
{
   p.Name,
   String.Join(",", p.Credentials.Select<Credentials, string>(c=>c.Abrev).ToArray())
}

Into the Select, I think x must be Credential, not Credentials...

EDIT

You need to move your objects into memory, try adding ToList() before make the Select

from p in Physicians.Include("Credentials").ToList()
select new
{
    p.Name,
    Credentials = String.Join(",", p.Credentials.Select<Credentials, string>(c=>c.Abrev).ToArray())
}