Question

I have a Linq expression that operates on a list of objects for which one of said objects properties I need to type check before making use of it.

Example:

IEnumerable<Employee> activeAuditOwners = (

    from objectStateEntry in objectStateEntries
    where ( objectStateEntry.Entity is IAuditEntity ) == true
       && ( objectStateEntry.Entity as IAuditEntity ).Active == true
    select ( objectStateEntry.Entity as IAuditEntity ).Owner

);

My concern is that I use type checking 3 times ( is, as, as ) which doesn’t feel very DRY.

Is there a better shape for this query that avoids this (without creating a second query)?

UPDATE: Thanks for the great answers, I have tidied the example a bit for future readers.

Answer 1

One way would be to use the let clause:

from auditObjectStateEntry in auditObjectStateEntries
let entity = auditObjectStateEntries.Entity as IAuditEntity
where entity != null
   && entity.Active
select entity.Owner