Question

this may be a very basic question but I haven’t used Linq much so do need help.
I want to retrieve a list of records based on the related record count.

for example:

I have contact entity which has 1:N relationship with a ‘Role’ entity. I want to select contacts that have

1. No related roles
2. only 1 related role

How do I write this using Linq

from contact in context.ContactSet
where <contact.Roles has no records> -- ?? 
select contact;

Please help.

Answer 1

You can check by using Count() <= 1

Linq style:

from contact in context.ContactSet
where contact.Roles.Count() <= 1
select contact;

Method style:

context.ContactSet.Where(c => c.Roles.Count() <= 1);