提供XML文件供asp.net c#中的大量记录下载

发布时间：2020-12-16 23:31:40 所属栏目：百科来源：网络整理

导读：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stream然后提供下载,所以我首先在磁盘上创建了xml文件将数据写入其中并尝试在byes中读取数据提供下载,然后从磁盘中删除文件.但是要获得“system.outofm

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stream&然后提供下载,所以我首先在磁盘上创建了xml文件&将数据写入其中并尝试在byes&中读取数据提供下载,然后从磁盘中删除文件.但是要获得“system.outofmemoryexception”
“Byte [] b = File.ReadAllBytes(filepath);”.

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("nr"," ")
                                  .Replace("n"," ").Replace("r"," "),Convert.ToString(dataRow[dataColumn]).Replace("nr"," ").Replace("n"," "));
                        }

         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？

解决方法

您可以直接将XmlWriter连接到Response OutputStream,而无需中间文件.通过将 BufferOutput设置为false,可以防止完整的repsonse在发送到客户端之前缓冲服务器端.

请注意,多个Replace语句将导致额外的内存压力/更多字符串被GC编辑.

string name = string.Format("attachment; filename={0:yyyyMMddHHmmss}.xml",DateTime.Now);
HttpContext.Current.Response.ContentType = "application/xml";
HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;

HttpContext.Current.Response.BufferOutput = false; //start streaming immideately

HttpContext.Current.Response.AppendHeader("Content-Disposition",name);

DataTable dataTable = dsData.Tables[0];             

XmlWriterSettings xws = new XmlWriterSettings { OmitXmlDeclaration = true };

using (XmlWriter xmlWriter = XmlWriter.Create(
         HttpContext.Current.Response.OutputStream,// The OutputStream of the HttpResponse
         xws))
{
  xmlWriter.WriteStartElement("root");

  var cleanedColNames = new Dictionary<DataColumn,string>();
  foreach (DataColumn dataColumn in dataTable.Columns)
  {
      cleanedColNames.Add(dataColumn,dataColumn.ColumnName.Replace("nr"," ")
                               .Replace("n"," ")
                               .Replace("r"," "));
  }

  foreach (DataRow dataRow in dataTable.Rows)
  {
    xmlWriter.WriteStartElement("datanode");
    foreach (DataColumn dataColumn in dataTable.Columns)
    {
         xmlWriter.WriteElementString(
             cleanedColNames[dataColumn]," ")
                                                  .Replace("n"," ")
                                                  .Replace("r"," "));
                        }
         xmlWriter.WriteEndElement();
     }
     xmlWriter.WriteEndElement();
     xmlWriter.Flush();
     xmlWriter.Close();
   }

HttpContext.Current.Response.End();

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!