Question

I have a site where a user can download a file. Some files are extremely large (the largest being 323 MB). When I test it to try and download this file I get an out-of-memory exception. The only way I know to download the file is below. The reason I’m using the code below is that the URL is encoded and I can’t let the user link directly to the file. Is there another way to download this file without having to read the whole thing into a byte array?

  FileStream fs = new FileStream(context.Server.MapPath(url),
                                 FileMode.Open,
                                 FileAccess.Read);

  BinaryReader br = new BinaryReader(fs);
  long numBytes = new FileInfo(context.Server.MapPath(url)).Length;
  byte[] bytes = br.ReadBytes((int) numBytes);

  string filename = Path.GetFileName(url);
  context.Response.Buffer = true;
  context.Response.Charset = "";

  context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
  context.Response.ContentType = "application/x-rar-compressed";
  context.Response.AddHeader("content-disposition", "attachment;filename=" + filename);

  context.Response.BinaryWrite(bytes);
  context.Response.Flush();
  context.Response.End();

Answer 1

Instead of

context.Response.BinaryWrite(bytes);

use

context.Response.TransmitFile(context.Server.MapPath(url));

This will avoid reading the entire file into memory.