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, Apr 05 '16 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, Apr 05 '16 at 16:33

score 230 · Accepted Answer · edited Oct 24 '18 at 00:15

230

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 '18 at 00:15

Samuel Liew

76,741
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answered Apr 05 '16 at 17:45

erdomke

4,980
1
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30

you could shorten the code by using the copy functions on IFormFile themselve. using (var stream = new MemoryStream()) { formFile.CopyTo(stream); return stream.ToArray(); } – Bosken85 Sep 19 '17 at 09:26
@Bosken85 Good catch! I updated the example to reflect your recommendations. – erdomke Sep 19 '17 at 17:19
8

You can also use `file.CopyToAsync(ms)` now. – David B Jan 31 '18 at 08:28
Any way I can copy only the first 20 bytes or so to the memory stream and byte array? Only need those to check the file signature – kanpeki Oct 18 '19 at 13:12
2

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); }` – erdomke Oct 18 '19 at 17:02
@erdomke why do we need file.CopyTo(ms);? – Roxy'Pro Nov 15 '19 at 20:11
@Roxy'pro That line reads the file contents into a MemoryStream (backed by a byte array) so that you can convert the byte array to base64. – erdomke Nov 17 '19 at 04:20

Rookian · Answer 2 · 2022-04-19T12:37:33.303

56

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 '22 at 12:37

answered Dec 16 '19 at 15:03

Rookian

19,841
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1

Miss *await* before formFile.GetBytes(); Or Am I Wrong? – Bruno Henri Jun 19 '20 at 19:26
1

Let's change method name to GetBytesAsync(), so this suffix will indicate this is async function – Mahmood Garibov Jun 25 '22 at 16:58
@MahmoodGaribov this won't happen as I don't see a point to add the suffix. See also: https://docs.particular.net/nservicebus/upgrades/5to6/async-suffix#reason-for-no-async-suffix – Rookian Jul 01 '22 at 09:14

score 6 · Answer 3 · answered Apr 05 '16 at 16:40

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);
      }
   }
}

Run a .jpg through this and see what you get. OP asks for _`byte`_ array. — Joshua, Dec 15 '21 at 18:38

score -1 · Answer 4 · answered Jul 17 '22 at 12:13

-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 '22 at 12:13

harili

406
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How to convert a file into byte array in memory?

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