C# ling to sql group by分组查询

(from b in _db.order_info
                             where b.status != 3
                             group new {  b.batchnumber, b.create_time } by new { b.merchant_id, b.batchnumber } into g
                             select new UserModel
                             {
                                
                                 batchnumber = g.Key.batchnumber,
                                 batchTime = g.Max(u => u.create_time)

                             }).OrderBy(p => p.batchTime).Take(20).ToList();

 

　　分组后，将多个id值合并为一个

    var a = ( from f in userInfo
                             group new { f.code, f.id } by new { f.code } into g
                             select new StuModel
                             {
                                 StuCode = g.Key.code.Trim(),
                                 Ids = string.Join(",", g.Select(m => m.id).ToList())
                             })?.ToList();