Hi Expert! 

Starting with the next entities definition:

Public Class Certificate{

  public  ID as int;

}

Public Class Authority{

  ID int;

  Certificates IEnumerable<Certificate>;

}

My function recives 2 collections: IEnumerable<Certificate> and IEnumerable<Authority>. I need to select the Authorities which Certificates collection has at least 

one Certificate in the IEnumerable<Certificate> input parameter.

My firt implementation is enumerating the IEnumerable<Certificate> and selecting the Authority using a Where(predicate).

Public IEnumerable<Authority> SelectAuthorities(authList IEnumerable<Authority>, certList IEnumerable<Certificate>){

  foreach (Certificate loadedCert in certList) {

    yield return auth.Where(a => a.Certificados.Any(c1 => c1.IDCert == loadedCert.IDCert));

  }  

}

I think there must be a way to avoid the for loop using a more complex linq correlated subquery (I feel it in the "force") but I can't find it.

Can anybody help?

Thanks in advance!