C# DataTable数据遍历优化详解

public static void Test2()
{
 Stopwatch watch = new Stopwatch();
 using (DbConnection conn = SqlHelper.GetConnection("ConnectionString"))
 {
  using (SqlCommand cmd = new SqlCommand())
  {
   watch.Start();
   cmd.CommandText = string.Format(@"
select ROW_NUMBER() OVER (Order by S.AccID,S.CurrID,S.AbsID,S.Flag)AS RowNum,S.* from Test S 
");
   cmd.Connection = conn as SqlConnection;
   cmd.CommandTimeout = 60000;
   conn.Open();
   DataTable table = ExecuteDataTable(cmd);
   watch.Stop();
   Console.WriteLine("从数据库取出数据{0}条", table.Rows.Count);
   Stopwatch watch2 = new Stopwatch();
   watch2.Start();
   DataTable newTable = HandleAccYear(table,true);
   watch2.Stop();
   Console.WriteLine("数据{0},遍历操作时间：毫秒：{1}，秒：{2}", newTable.Rows.Count, watch2.ElapsedMilliseconds, watch2.ElapsedMilliseconds / 1000);
  }
  conn.Close();
 }
}

public static DataTable ExecuteDataTable(SqlCommand cmd)
{
  DataTable table = new DataTable();
  SqlDataAdapter adaper = new SqlDataAdapter(cmd);
  adaper.Fill(table);
  return table;
}

private static DataTable HandleAccYear(DataTable dt, bool isCurrency)
{
  DataTable newdt = dt.Clone();
  //不使用主键
  //dt.PrimaryKey = new DataColumn[] {
  // dt.Columns["AccID"],
  // dt.Columns["Flag"],
  // dt.Columns["AbsID"],
  // dt.Columns["RowNum"],
  //};
  if (dt.Rows.Count > 0)
  {
   object flag = null;
   foreach (DataRow row in dt.Rows)
   {
    flag = row["Flag"];
    if (flag != null && !Helper.AreEqual(flag.ToString(), "1"))
    {
     DataRow newRow = newdt.NewRow();
     DataRow sourceRow = newdt.NewRow();
     sourceRow.ItemArray = row.ItemArray;
     newRow.ItemArray = row.ItemArray;
     string accID = row["AccID"].ToString(),
      year = row["Y"].ToString(),
      absID = row["AbsID"].ToString();
     newRow["Flag"] = "5";
     newRow["SumInfo"] = "测试数据";
     string filter = "AccID='" + accID + "' AND Y='" + year + "' AND AbsID <= " + absID;
     if (!isCurrency)
     {
      filter = "AccID='" + accID + "'AND CurrID='" + row["CurrID"] + "' AND Y='" + year + "' AND AbsID <= " + absID;
     }
     DataRow[] selectRow = dt.Select(filter);
     double debitLC = 0, debitQty = 0, creditLC = 0, creditQty = 0, debitFC = 0, creditFC = 0;
     foreach (DataRow item in selectRow)
     {
      debitLC += ToDouble(item["YearDebitLC"]);
      debitQty += ToDouble(item["YearDebitQty"]);
      creditLC +=ToDouble(item["YearCreditLC"]);
      creditQty += ToDouble(item["YearCreditQty"]);
      if (!isCurrency)
      {
       debitFC += ToDouble(item["YearDebitFC"]);
       creditFC += ToDouble(item["YearCreditFC"]);
      }
     }
     newRow["CurDebitLC"] = debitLC;
     newRow["CurDebitQty"] = debitQty;
     newRow["CurCreditLC"] = creditLC;
     newRow["CurCreditQty"] = creditQty;
     //newRow["CurDebitLC"] = dt.Compute("Sum(YearDebitLC)", filter);
     //newRow["CurDebitQty"] = dt.Compute("Sum(YearDebitQty)", filter);
     //newRow["CurCreditLC"] = dt.Compute("Sum(YearCreditLC)", filter);
     //newRow["CurCreditQty"] = dt.Compute("Sum(YearCreditQty)", filter);
     if (!isCurrency)
     {
      //newRow["CurCreditFC"] = dt.Compute("Sum(YearCreditFC)", filter);
      //newRow["CurDebitFC"] = dt.Compute("Sum(YearDebitFC)", filter);
      newRow["CurCreditFC"] = creditFC;
      newRow["CurDebitFC"] = debitFC;
     }
     newdt.Rows.Add(sourceRow);
     newdt.Rows.Add(newRow);
    }
    else
    {
     DataRow sourceRow = newdt.NewRow();
     sourceRow.ItemArray = row.ItemArray;
     newdt.Rows.Add(sourceRow);
    }
   }
  }
  return newdt;
 }

int sid = dt.Rows.Count % 100 == 0 ? (dt.Rows.Count / 100) : (dt.Rows.Count / 100 + 1);
    for (int a = 1; a <= sid; a++)
    {
     object aa=a.ToString() + "," + sid.ToString();
     ThreadPool.QueueUserWorkItem(todo
      , aa);
    }
 public void todo(object aa)
 {
  string sql = "";
  int startindex = Convert.ToInt32(aa.ToString().Split(',')[0]);
  int limitstep = Convert.ToInt32(aa.ToString().Split(',')[1]);
  for (int i = (startindex > 1 ? ((startindex - 1) * 100) : 0); i < (startindex == limitstep ? (dt.Rows.Count) : startindex*100); i++)
  {
   //todo数据操作
  }
  Thread.Sleep(2000);
 }