Using LINQ to Objects to find items in one collection that do not match another

Question

I want to find all items in one collection that do not match another collection. The collections are not of the same type, though; I want to write a lambda expression to spe

Answer 1

Its better if you left join the item and filter with null condition

var finalcertificates = (from globCert in resultCertificate
                                         join toExcludeCert in certificatesToExclude
                                             on globCert.CertificateId equals toExcludeCert.CertificateId into certs
                                         from toExcludeCert in certs.DefaultIfEmpty()
                                         where toExcludeCert == null
                                         select globCert).Union(currentCertificate).Distinct().OrderBy(cert => cert.CertificateName);