比较两个DataTable的字段（高效）

var query1 = from r in dt.AsEnumerable()
from rr in dt2.AsEnumerable()
where Convert.ToInt32(r.Field<string>("sdtdie")) > Convert.ToInt32(rr.Field<string>("sdtdie"))
//where r.Field<int>("sdtdie") > rr.Field<int>("sdtdie")
where r.Field<string>("meslotname").Equals(rr.Field<string>("meslotname"))
where r.Field<string>("machinename").Equals(rr.Field<string>("machinename"))
where r.Field<string>("processstep").Equals(rr.Field<string>("processstep"))

if (query1.Count() > 0)
{
DataTable dtResult = query1.CopyToDataTable();
}