ASP MVC FileStreamResult OutOfMemoryException

Question

I have a large zip file (500MB or greater) that I am reading into a MemoryStream and return as a FileStreamResult. However, I am getting a OutOfMemory Exception for files over 200MB. Within my Action I have the following code:

MemoryStream outputStream = new MemoryStream();
using (var fs = new FileStream(filepath, FileMode.Open, FileAccess.Read))
{
   //Response.BufferOutput = false;   // to prevent buffering
   byte[] buffer = new byte[1024];
   int bytesRead = 0;
   while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) > 0)
   {
      outputStream.Write(buffer, 0, bytesRead);
   }
}

outputStream.Seek(0, SeekOrigin.Begin);
return new FileStreamResult(outputStream, content_type);

I do not want to use ReadAllBytes because of 2GB limit and also because of the memory issues when reading entire file into memory at once. — user327999
– user327999, Commented Apr 4, 2012 at 14:25

Community · Accepted Answer · 2017-05-23 10:29:12Z

2

You could try the solution proposed on this page:

OutOfMemoryException when sending a big file 500mb using filestream

It shows how to read the file into an IStream and send the Response.

edited May 23, 2017 at 10:29

CommunityBot

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answered Apr 4, 2012 at 14:38

SwDevMan81

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1 Comment

RayLoveless Over a year ago

This should be marked as the answer. Link worked for me. Thanks.

Fionn · Accepted Answer · 2012-04-04 14:47:56Z

2

If you read the file into a MemoryStream you still need to allocate the memory for the whole file, as internally the MemoryStream is nothing else than a byte array.

So currently you are reading your file into a large memory buffer using a smaller intermediate (also in memory) buffer.

Why not forward the file stream directly to the FileStreamResult?

using (var fs = new FileStream(filepath, FileMode.Open, FileAccess.Read))
{
    return new FileStreamResult(fs, content_type); 
}

answered Apr 4, 2012 at 14:47

Fionn

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3 Comments

user327999 Over a year ago

I am getting a The process cannot access the file because it is being used by another process when trying this approach.

Fionn Over a year ago

Sorry that the answer is so late, didn't notice it earlier. This should help: new FileStream(filepath, FileMode.Open, FileAccess.Read, FileShare.Read). It allows multiple opening of the file as long as it is read access.

RayLoveless Over a year ago

Couldn't get this to work. If I remove the using's it gives out of memory exception. If it include the Using my mvc app is 302 re-directing to our error page...Not sure why.

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