@kjgilla: A different but possibly simpler approach could be,

n = n
    .Distinct
    (
        System.Collections.Generic.EqualityComparer<dynamic>.Create
        (
            (x, y) => x?.Vchr == y?.Vchr,
            o = o.Vchr.GetHashCode() ^ o.Id.GetHashCode() ^ o.Ctr.GetHashCode() ^ o.Vendor.GetHashCode() ^ o.Description.GetHashCode() ^ o.Invoice.GetHashCode()
        )
    )
    .ToList();