C#两个集合多属性组合关联得到新的组合

C#两个集合多属性组合关联得到新的组合

代码

var isLackGroupA = useList.Select(d => new
                                    {
                                        billType = Convert.ToInt32(d["FBILLTYPEID"]),
                                        fid = Convert.ToInt64(d["FID"]),
                                        groupId = Convert.ToInt64(d["FREPLACEGROUP"]),
                                    }).Distinct().ToList();
var isLackList = (from a in isLackGroupA
                    join b in useList
                    on a equals new
                    {
                        billType = Convert.ToInt32(b["FBILLTYPEID"]),
                        fid = Convert.ToInt64(b["FID"]),
                        groupId = Convert.ToInt64(b["FREPLACEGROUP"])
                    }
                    into c
                    from d in c.DefaultIfEmpty()
                    select d
                        )
                        .ToList();