DataTabe使用Linq实现 Group

DataTable dt = dataSet.Tables[];
var query = from t in dt.AsEnumerable()
            group t by new { t1 = t.Field<string>("username"), t2 = t.Field<string>("department"), t3 = t.Field<string>("sex") } into m
    select new
    {
        username = m.Key.t1,
        department = m.Key.t2,
        sex = m.Key.t3
    };