提供XML文件供asp.net c#中的大量记录下载

我需要提供xml文件以便下载6,00,000条记录(数据可能会增加)但不允许将文件保存在磁盘上.我直接将xml写入流然后提供下载时遇到问题,所以我首先在磁盘上创建了xml文件并将数据写入其中并尝试读取它并提供下载然后从磁盘中删除文件.但是在"Byte [] b = File.ReadAllBytes(filepath);"中获取"system.outofmemoryexception".

以下是我的代码:

string name = string.Format("{0:yyyyMMddHHmmss}", DateTime.Now);
string filename = "TestFile.xml";

string filepath = ConfigurationManager.AppSettings["XmlFiles"] + "\\" + filename;


DataTable dataTable = dsData.Tables[0];             

FileStream fs =new FileStream(filepath, FileMode.Create);
XmlWriterSettings xws = new XmlWriterSettings { OmitXmlDeclaration = true };
using (XmlWriter xmlWriter = XmlWriter.Create(fs,xws))
{

  xmlWriter.WriteStartElement("root");

  foreach (DataRow dataRow in dataTable.Rows)
  {
    xmlWriter.WriteStartElement("datanode");
    foreach (DataColumn dataColumn in dataTable.Columns)
    {
     xmlWriter.WriteElementString(dataColumn.ColumnName.Replace("\n\r", " ")
                                  .Replace("\n", " ").Replace("\r", " "), Convert.ToString(dataRow[dataColumn]).Replace("\n\r", " ").Replace("\n", " ").Replace("\r", " "));
                        }

         xmlWriter.WriteEndElement();
     }
     xmlWriter.WriteEndElement();
     xmlWriter.Flush();
     xmlWriter.Close();
   }

   fs.Close();
   Byte[] b = File.ReadAllBytes(filepath);                
   if (File.Exists(filepath))
      File.Delete(filepath);

string s = string.Format("{0:yyyyMMddHHmmss}", DateTime.Now);
HttpContext.Current.Response.ContentType = "application/xml";
HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;
HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment; filename=" + s + ".xml" + "");
HttpContext.Current.Response.BinaryWrite(b);
HttpContext.Current.Response.End();

还有其他方法可以处理大量记录吗？