//注意结帖
var query=from si in steelBlade_info
let ids=steelBlade_info.Where(s=>Nullable<DateTime>.Equals(s.UseBeginTime,null))
.GroupBy(s=>s.steelBladeType+s.steelBladeLength)
.Select(g=>g.Min(t=>t.InWHTime))
where ids.Contains(si.InWHTime)
orderby si.steel,si.InWHTime
select new {...}
var query =
from t in ds.Tables[0].AsEnumerable()
where Convert.ToInt32(t.Field<string>("gather_month")) <= b1
select t;
var query2 =
from t in ds.Tables[0].AsEnumerable()
from o in query.AsEnumerable()
where t.Field<string>("user_no").Contains(o.Field<string>("user_no"))
orderby t.Field<string>("volpage"), t.Field<string>("user_no")
select t;
