How to convert a file into byte array in memory?

Question

Here is my code:

 public async Task<IActionResult> Index(ICollection<IFormFile> files)
 {
    foreach (var file in files)
        uploaddb(file);   

    var uploads = Path.Combine(_environment.WebRootPath, "uploads");
    foreach (var file in files)
    {
        if (file.Length > 0)
        {
            var fileName = ContentDispositionHeaderValue.Parse(file.ContentDisposition).FileName.Trim('"');

            await file.SaveAsAsync(Path.Combine(uploads, fileName));
        }
    }
}

Now I am converting this file into byte array using this code:

var filepath = Path.Combine(_environment.WebRootPath, "uploads/Book1.xlsx");
byte[] fileBytes = System.IO.File.ReadAllBytes(filepath);
string s = Convert.ToBase64String(fileBytes);

And then I am uploading this code into my nosql database.This is all working fine but the problem is i don't want to save the file. Instead of that i want to directly upload the file into my database. And it can be possible if i can just convert the file into byte array directly without saving it.

public async Task<IActionResult> Index(ICollection<IFormFile> files)
{
    foreach (var file in files)
        uploaddb(file);   
    var uploads = Path.Combine(_environment.WebRootPath, "uploads");
    foreach (var file in files)
    {
        if (file.Length > 0)
        {
            var fileName = ContentDispositionHeaderValue.Parse(file.ContentDisposition).FileName.Trim('"');

///Code to Convert the file into byte array
}

file.OpenReadStream() look for the documentation of IFormFile.OpenReadStream — Gusman
– Gusman, Commented Apr 5, 2016 at 16:32
When you originally saved the file, what form was it in? However you had it in memory, it should have already been a byte array, or convertible to a byte array. We would need to see how you are obtaining the file in the first place, and how you are saving it. — Kevin
– Kevin, Commented Apr 5, 2016 at 16:33

Samuel Liew · Accepted Answer · 2018-10-24 00:15:34Z

244

As opposed to saving the data as a string (which allocates more memory than needed and might not work if the binary data has null bytes in it), I would recommend an approach more like

foreach (var file in files)
{
  if (file.Length > 0)
  {
    using (var ms = new MemoryStream())
    {
      file.CopyTo(ms);
      var fileBytes = ms.ToArray();
      string s = Convert.ToBase64String(fileBytes);
      // act on the Base64 data
    }
  }
}

Also, for the benefit of others, the source code for IFormFile can be found on GitHub

edited Oct 24, 2018 at 0:15

Samuel Liew

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answered Apr 5, 2016 at 17:45

erdomke

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7 Comments

Bosken85 Over a year ago

you could shorten the code by using the copy functions on IFormFile themselve. using (var stream = new MemoryStream()) { formFile.CopyTo(stream); return stream.ToArray(); }

erdomke Over a year ago

@Bosken85 Good catch! I updated the example to reflect your recommendations.

David B Over a year ago

You can also use file.CopyToAsync(ms) now.

erdomke Over a year ago

Something to the effect of the following should help you out. using (var stream = file.OpenReadStream()) { var buffer = new byte[20]; stream.Read(buffer, 0, 20); }

Roxy'Pro Over a year ago

@erdomke why do we need file.CopyTo(ms);?

|

Rookian · Accepted Answer · 2022-04-19 12:37:33Z

63

You can just write a simple extension:

public static class FormFileExtensions
{
    public static async Task<byte[]> GetBytes(this IFormFile formFile)
    {
        await using var memoryStream = new MemoryStream();
        await formFile.CopyToAsync(memoryStream);
        return memoryStream.ToArray();
    }
}

Usage

var bytes = await formFile.GetBytes();
var hexString = Convert.ToBase64String(bytes);

edited Apr 19, 2022 at 12:37

answered Dec 16, 2019 at 15:03

Rookian

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5 Comments

Bruno Henri Over a year ago

Miss await before formFile.GetBytes(); Or Am I Wrong?

Mahmood Garibov Over a year ago

Let's change method name to GetBytesAsync(), so this suffix will indicate this is async function

Rookian Over a year ago

@MahmoodGaribov this won't happen as I don't see a point to add the suffix. See also: docs.particular.net/nservicebus/upgrades/5to6/…

Hendrik Clercx Over a year ago

The reason you missed the await is because you don't have the 'Async' suffix. So that already proves its point, next it's considered good practise to have this suffix.

Rookian Over a year ago

The reason was that I did not use an IDE.

Cat_Clan · Accepted Answer · 2016-04-05 16:40:24Z

7

You can use the following code to convert it to a byte array:

foreach (var file in files)
{
   if (file.Length > 0)
    {
      var fileName = ContentDispositionHeaderValue.Parse(file.ContentDisposition).FileName.Trim('"');
      using (var reader = new StreamReader(file.OpenReadStream()))
      {
        string contentAsString = reader.ReadToEnd();
        byte[] bytes = new byte[contentAsString.Length * sizeof(char)];
        System.Buffer.BlockCopy(contentAsString.ToCharArray(), 0, bytes, 0, bytes.Length);
      }
   }
}

answered Apr 5, 2016 at 16:40

Cat_Clan

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1 Comment

Joshua Over a year ago

Run a .jpg through this and see what you get. OP asks for byte array.

harili · Accepted Answer · 2022-07-17 12:13:45Z

-1

You can retrieve your file by using the Request.Form already implemented (as image for instance) :

var bytes = new byte[Request.Form.Files.First().Length];
var hexString = Convert.ToBase64String(bytes);

Hope it help

answered Jul 17, 2022 at 12:13

harili

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