ADO.NET

DataTable dtTable = null;
using (SqlConnection connSelect = new SqlConnection(_connFirst))
{
    try
    {
        connSelect.Open();
        string strSql = "select BarcodeCompInfo.*,WorkOrder.ContractID from BarcodeCompInfo left join WorkOrder on BarcodeCompInfo.WorkOrderID=WorkOrder.WorkOrderID where BarcodeCompInfo.AID>=" + begin + " and BarcodeCompInfo.AID<" + end;
        SqlDataAdapter myDp = new SqlDataAdapter(strSql, connSelect);
        DataSet ds = new DataSet();
        myDp.Fill(ds);
        connSelect.Close();

        dtTable = ds.Tables[0];
    }
    catch { }
}

using (SqlConnection connInsert = new SqlConnection(_connSecond))
{
      connInsert.Open();
      SqlCommand command = new SqlCommand(strSql, connInsert);
      command.CommandType = CommandType.Text;
      command.ExecuteNonQuery();
      connInsert.Close();
}