How to use Linq to query a table dependent on where a user belongs to another table

Question

I have a simple issue that's running me around, I would like to find out how I can use linq to query a subset of data, e.g. I have a table that contains certificates, certificates belong to a company and a company has users that belong to it and the view is basically supposed to only display certificates for a company whereby the current user is linked to. This is what I currently have and battling with the correct syntax for an exist statement or subquery?

public List<CertificateListItemModel> GetUserCertificates()
{
    var certificates = (from p in _db.Certificates
                        **where(
                                from bu2 in _db.BusinessUsers
                                where p.BusinessId == bu2.BusinessId && bu2.Email == _user.Name
                                //select new {}
                        )**
                        select new CertificateListItemModel
                        {
                            ...
                        })
                        .Distinct().ToList();

    return certificates;
}

Answer 1

I managed to resolve my issue with a simpler way and it seems it was not that difficult. The above solution confused me and I failed to implement it. Please find the simpler solution below. I just need to add the Where with a bool condition

var applications = (_db.Certificates
                    .Join(_db.BillingItems, p => p.CertificateId, bi => bi.CertificateId, (p, bi) => new {p, bi})
                    .Where(@t => (_db.BusinessUsers.Any(c => c.CbrBusinessId == @t.p.CbrOwnerRef && c.Email == _user.Name)))
                    .Select(@t => new CertificateListItemModel
                    {
                        CertificateId = @t.p.CertificateId,
                        ApplicationRefNo = @t.p.ApplicationReferenceNo,
                        ApplicationStatus = @t.p.ApplicationStatus,
                        SubmittedDateTime = @t.p.SubmittedDateTime,
                        IssuingLocation = @t.p.DesiredIssueLocation,
                        BillingId = @t.bi.BillingId,
                        PaperNo = @t.bi.PaperNo,
                        InvoiceNo = @t.bi.InvoiceNo,
                        BillingStatus = @t.bi.BillingStatus,
                        InvoiceRefNo = @t.bi.PaperNo,
                        BillingParty = @t.bi.BillingParty
                    }))
                    .Distinct().ToList();

                return applications;