我认为您在这里不需要Distinct，而需要Exists(或在Linq中称为Any)

I dont think you need a Distinct here but a Exists (or Any as it is called in Linq)

尝试一下:

    var q = (from p in context.Practitioners
            where context.ProviderNetworks.Any(pn => pn.ProviderId == p.ProviderId && notNetworkIds.Contains(pn.Network))
            orderby p.UpdateDate descending
            select p).Skip(PageSize * (pageOffset ?? 0)).Take(PageSize).ToList();