SelectMany applied to 3 lists

Question

I need to create a list of objects, OrganizationEnrolment, created using 3 Entity Framework entities (User, EnrolmentType and OrganizationEnrolment):

List<OrganizationEnrolment> organizationEnrolments = 
  context.Organizations
  .SelectMany(x => context.Users)
  .SelectMany(x => context.EnrolmentTypes)
  .Select(y => new OrganizationEnrolment {
     EnrolmentType = enrolmentType
     Organization = organization,
     User = user
   })

My problem is after having the SelectMany how to get the enrolmentType, organization and user from the 3 joined table? Note that the following code:

EnrolmentType = enrolmentType,
Organization = organization,
User = user

is not working because I do not have the variables enrolmentType, organization and user.

Answer 1

You can use query syntax to get all those variables:

from o in context.Organizations
from u in context.Users
from et in context.EnrolmentTypes
select new OrganizationEnrolment {
     EnrolmentType = et
     Organization = o,
     User = u
   }

Each local range variable will be visible in select statement.

Lambda syntax (checked with EF6):

context.Organizations.SelectMany(
          o => context.Users.SelectMany(
              u => context.EnrolmentTypes.Select(
                  et => new OrganizationEnrolment {
                       EnrolmentType = et
                       Organization = o,
                       User = u
                  })
              )
         )