DataSet ds = LoadDataSetUsingDataAdapter();

var highDiscountOrders =
from o in ds.Tables["OrderDetails"].AsEnumerable()
where o.Field<float?>("Discount") > 0.2
select o;

DataTable selectionTable = highDiscountOrders.CopyToDataTable();

var lowDiscountOrders =
from o in ds.Tables["OrderDetails"].AsEnumerable()
where o.Field<float?>("Discount") < 0.05
select o;

lowDiscountOrders.CopyToDataTable( selectionTable,LoadOption.PreserveChanges);
