c# dataTable 排序

 if(columnBindingName== "modifyfrequency")
                {
                   
                    DataTable dt = this.dgvMyIndex.DataSource as DataTable;
                    EnumerableRowCollection<DataRow> dayquery =
    from order in dt.AsEnumerable()  where order.Field<string>("modifyfrequency") == "日" 
    select order;
                    EnumerableRowCollection<DataRow> weekquery =
  from order in dt.AsEnumerable()
  where order.Field<string>("modifyfrequency") == "周"
  select order;
                    EnumerableRowCollection<DataRow> xunquery =
from order in dt.AsEnumerable()
where order.Field<string>("modifyfrequency") == "旬"
select order;
                    EnumerableRowCollection<DataRow> halfMonthquery =
from order in dt.AsEnumerable()
where order.Field<string>("modifyfrequency") == "半月"
select order;
                    EnumerableRowCollection<DataRow> monthquery =
  from order in dt.AsEnumerable()
  where order.Field<string>("modifyfrequency") == "月"
  select order;
                    EnumerableRowCollection<DataRow> quaterquery =
 from order in dt.AsEnumerable()
 where order.Field<string>("modifyfrequency") == "季度"
 select order;
                    EnumerableRowCollection<DataRow> halfYearquery =
from order in dt.AsEnumerable()
where order.Field<string>("modifyfrequency") == "半年"
select order;
                    EnumerableRowCollection<DataRow> Yearquery =
from order in dt.AsEnumerable()
where order.Field<string>("modifyfrequency") == "年"
select order;
                    EnumerableRowCollection<DataRow> budingqiquery =
from order in dt.AsEnumerable()
where order.Field<string>("modifyfrequency") == "不定期"
select order;
                    EnumerableRowCollection<DataRow> daidingquery =
from order in dt.AsEnumerable()
where order.Field<string>("modifyfrequency") == "待定"
select order;
                    DataTable newDataTable = dt.Clone();
                    if (sortMode=="asc")
                    {
                       

                        foreach (var row in dayquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in weekquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in xunquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in halfMonthquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in monthquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in quaterquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in halfYearquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in Yearquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in budingqiquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                        foreach (var row in daidingquery)
                        {
                            newDataTable.Rows.Add(row.ItemArray);
                        }
                    }

                }