如何使用 Linq 根据用户属于另一个 table 的位置查询 table

Question

我有一个运行我身边的简单问题，我想了解如何使用 linq 来查询数据子集，例如我有一个包含证书的 table，证书属于一家公司，一家公司有属于它的用户，并且该视图基本上应该只显示当前用户链接到的公司的证书。这就是我目前所拥有的，并且正在与存在语句或子查询的正确语法作斗争？

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

这应该 return 您属于公司 _user 分配给的不同证书列表（假设 _user.Name 和 businessUser.Email 如果相同，则确实具有相同的内容用户）。

var certificates = _db.Certificates
                      .Join(_db.Businesses,
                            certificate => certificate.BusinessId,
                            business => business.Id,
                            (certificate, business) => new { certificate, business })
                      .Join(_db.BusinessUsers.Where(user => user.Email = _user.Name),
                            certificateAndBusiness => certificateAndBusiness.business.Id,
                            businessUser => businessUser.BusinessId,
                            (certificateAndBusiness, businessUser) => certificate)
                      .GroupBy(certificate => certificate.Id)
                      .Select(certificates => certificates.First())
                      .Select(certificate => new CertificateListItemModel() {...})
                      .ToList()
```

Answer 2

我设法用更简单的方法解决了我的问题，看起来并没有那么困难。上面的解决方案让我很困惑，我没有实现它。请在下面找到更简单的解决方案。我只需要添加带有布尔条件的 Where

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;

如何使用 Linq 根据用户属于另一个 table 的位置查询 table

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

c#

sql

linq

entity-framework

linq-to-sql