Entity framework 通过linq查询获取组中最新记录的ID

下面的linq查询包含一些连接，我需要获取一个实体的最新记录Id，其Id字段为“sonuc”

var query = (from type1 in lohusaHastaRepo
    join type2 in hastaRepo on lohusa.HastaTC equals hasta.HastaTC
    join type3 in gebeSonucBildirimRepo on lohusa.HastaTC equals sonuc.HastaTC
    group type1 by hasta.HastaTC into grp
    select new SomeModel()
    {
        Type3ID = 0,//I want to get 'ID' of latest records of 'sonuc' entity 
        Type1ID = grp.OrderByDescending(o=>o.BirthDate).Select(s=>s.ID).FirstOrDefault()
    });

这：

上面给了我'type1'实体的Id，我还需要'type3'的Id

---

我怎样才能做到这一点？

我认为应该这样做：

var query = (from type1 in lohusaHastaRepo
    join type2 in hastaRepo on lohusa.HastaTC equals hasta.HastaTC
    join type3 in gebeSonucBildirimRepo on lohusa.HastaTC equals sonuc.HastaTC
    group new {type1, type3} by hasta.HastaTC into grp
    select new SomeModel()
    {
        Type3ID = grp
            .Select(e => e.type3)
            .OrderByDescending(o=>o.BirthDate)
            .Select(s=>s.ID)
            .FirstOrDefault(),
        Type1ID = grp
            .Select(e => e.type1)
            .OrderByDescending(o=>o.BirthDate)
            .Select(s=>s.ID)
            .FirstOrDefault(),
    });

不过，我不能说它的表现会有多好。您可能希望在大型数据集上测试它，并考虑将其拆分为两个独立的往返行程：

var type1IDs = sonuc.GroupBy(s => s.HastaTC)
    .Select(g => new 
    {
        HastaTC = g.Key,
        ID = g.OrderByDescending(o=>o.BirthDate)
            .Select(s=>s.ID)
            .FirstOrDefault()
    });

var type3IDs = lohusa.GroupBy(s => s.HastaTC)
    .Select(g => new 
    {
        HastaTC = g.Key,
        ID = g.OrderByDescending(o=>o.BirthDate)
            .Select(s=>s.ID)
            .FirstOrDefault()
    });

---

@我编辑了这篇文章，希望对你有所帮助

var type1IDs = sonuc.GroupBy(s => s.HastaTC)
    .Select(g => new 
    {
        HastaTC = g.Key,
        ID = g.OrderByDescending(o=>o.BirthDate)
            .Select(s=>s.ID)
            .FirstOrDefault()
    });

var type3IDs = lohusa.GroupBy(s => s.HastaTC)
    .Select(g => new 
    {
        HastaTC = g.Key,
        ID = g.OrderByDescending(o=>o.BirthDate)
            .Select(s=>s.ID)
            .FirstOrDefault()
    });