使用LinQ with groupby和Max（）函数

Question

我试图用LINQ语法编写以下查询：

SELECT        Patient.PatientIDA, MAX(TxFieldPoint.EditDttm) AS Expr1
FROM            Patient INNER JOIN
                         TxSite ON Patient.PatientIDA = TxSite.PatientIDA INNER JOIN
                         TxField ON TxSite.SiteId = TxField.SiteId INNER JOIN
                         TxFieldPoint ON TxField.FldId = TxFieldPoint.FldId
GROUP BY Patient.PatientIDA
ORDER BY Patient.PatientIDA

我正在谈论这个：

var PtsList = from pt in dc.Patient
                          join site in dc.TxSite on pt.PatientIDA equals    site.PatientIDA
                          join fld in dc.TxField on site.SiteId equals fld.SiteId
                          join fldpnt in dc.TxFieldPoint on fld.FldId equals fldpnt.FldId                          
                          group new { pt, fldpnt } by new { fldpnt.EditDttm } into pt_fldpnt
                          select new cPtData
                          {
                              pt_name = pt_fldpnt.FirstOrDefault().pt.LastName,
                              pt_firstname = pt_fldpnt.FirstOrDefault().pt.FirstName,
                              pt_hospitalID = pt_fldpnt.FirstOrDefault().pt.PatientIDA,
                              chart_lasteditdttm = pt_fldpnt.Max(m => m.fldpnt.EditDttm).Value.Date,
                          };

根据我在本网站上阅读的其他帖子。这是行不通的。非常感谢帮助。