void UpdateParentsChildren(int?parentIDnullable, int childID) { // Even after checking parentIDnullable != null // int parentID = parentIDnullable gives an error. // v2 = v1 ?? default(int); equals: v2 = v1 == null ? default(int) : v1; int parentID = parentIDnullable ?? 100000; Candidate parent = db.Candidates.Find(parentID); if (parent != null) { //System.Diagnostics.Debug.WriteLine("Adding " + childID + " to " + parentID); parent.AddChild(childID); db.SaveChanges(); } }