Provide XML file for download with large number of records in asp.net c#

asp.net, c#, download, xml

Solution

You can directly hookup the XmlWriter to the Response OutputStream without the need for an intermediate file. By setting BufferOutput to `false` you prevent that the complete repsonse is buffered server side before being send to the client.

Do notice that the multiple Replace statements will lead to extra memory pressure/more strings to be GC-ed.

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("\n\r", " ")
                               .Replace("\n", " ")
                               .Replace("\r", " "));
  }

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

HttpContext.Current.Response.End();

Problem

I need to provide xml file for download around with 6,00,000 records(data may increase) but not allowed to save file on disk. I was facing issue in directly writing xml to stream & then providing for download , so i have first created xml file on disk & writing data to it and trying to read it in byes & provide for download and then delete file from disk. But getting "system.outofmemoryexception" in "Byte[] b = File.ReadAllBytes(filepath);". Below is my code: ``` 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(); ``` Is there any other way to handle large number of records?

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